Ergebnis für URL: http://www.w3.org/TR/REC-xml [1] W3C
Extensible Markup Language (XML) 1.0 (Fifth Edition) W3C Recommendation 26 November
2008
Note: On 7 February 2013, this specification was modified in place to replace
broken links to RFC4646 and RFC4647.
This version:
[2]http://www.w3.org/TR/2008/REC-xml-20081126/
Latest version:
[3]http://www.w3.org/TR/xml/
Previous versions:
[4]http://www.w3.org/TR/2008/PER-xml-20080205/
[5]http://www.w3.org/TR/2006/REC-xml-20060816/
Editors:
Tim Bray, Textuality and Netscape [6]
Jean Paoli, Microsoft [7]
C. M. Sperberg-McQueen, W3C [8]
Eve Maler, Sun Microsystems, Inc. [9]
François Yergeau
Please refer to the [10]errata for this document, which may include some normative
corrections.
The [11]previous errata for this document, are also available.
See also [12]translations.
This document is also available in these non-normative formats: [13]XML and [14]XHTML
with color-coded revision indicators.
[15]Copyright © 2008 [16]W3C^® ([17]MIT, [18]ERCIM, [19]Keio), All Rights Reserved. W3C
[20]liability, [21]trademark and [22]document use rules apply.
____________________________________________________________________________
Abstract
The Extensible Markup Language (XML) is a subset of SGML that is completely described
in this document. Its goal is to enable generic SGML to be served, received, and
processed on the Web in the way that is now possible with HTML. XML has been designed
for ease of implementation and for interoperability with both SGML and HTML.
Status of this Document
This section describes the status of this document at the time of its publication.
Other documents may supersede this document. A list of current W3C publications and the
latest revision of this technical report can be found in the [23]W3C technical reports
index at http://www.w3.org/TR/.
This document specifies a syntax created by subsetting an existing, widely used
international text processing standard (Standard Generalized Markup Language, ISO
8879:1986(E) as amended and corrected) for use on the World Wide Web. It is a product
of the [24]XML Core Working Group as part of the [25]XML Activity. The English version
of this specification is the only normative version. However, for translations of this
document, see [26]http://www.w3.org/2003/03/Translations/byTechnology?technology=xml.
This document is a [27]W3C Recommendation. This fifth edition is not a new version of
XML. As a convenience to readers, it incorporates the changes dictated by the
accumulated errata (available at [28]http://www.w3.org/XML/xml-V10-4e-errata) to the
[29]Fourth Edition of XML 1.0, dated 16 August 2006. In particular, erratum [30][E09]
relaxes the restrictions on element and attribute names, thereby providing in XML 1.0
the major end user benefit currently achievable only by using XML 1.1. As a
consequence, many possible documents which were not well-formed according to previous
editions of this specification are now well-formed, and previously invalid documents
using the newly-allowed name characters in, for example, ID attributes, are now valid.
This edition supersedes the previous [31]W3C Recommendation of 16 August 2006.
Please report errors in this document to the public [32]xml-editor@w3.org mail list;
public [33]archives are available. For the convenience of readers, an [34]XHTML version
with color-coded revision indicators is also provided; this version highlights each
change due to an erratum published in the [35]errata list for the previous edition,
together with a link to the particular erratum in that list. Most of the errata in the
list provide a rationale for the change. The errata list for this fifth edition is
available at [36]http://www.w3.org/XML/xml-V10-5e-errata.
An implementation report is available at
[37]http://www.w3.org/XML/2008/01/xml10-5e-implementation.html. A [38]Test Suite is
maintained to help assessing conformance to this specification.
This document has been reviewed by W3C Members, by software developers, and by other
W3C groups and interested parties, and is endorsed by the Director as a W3C
Recommendation. It is a stable document and may be used as reference material or cited
from another document. W3C's role in making the Recommendation is to draw attention to
the specification and to promote its widespread deployment. This enhances the
functionality and interoperability of the Web.
W3C maintains a [39]public list of any patent disclosures made in connection with the
deliverables of the group; that page also includes instructions for disclosing a
patent. An individual who has actual knowledge of a patent which the individual
believes contains [40]Essential Claim(s) must disclose the information in accordance
with [41]section 6 of the W3C Patent Policy.
Table of Contents
1 [42]Introduction
1.1 [43]Origin and Goals
1.2 [44]Terminology
2 [45]Documents
2.1 [46]Well-Formed XML Documents
2.2 [47]Characters
2.3 [48]Common Syntactic Constructs
2.4 [49]Character Data and Markup
2.5 [50]Comments
2.6 [51]Processing Instructions
2.7 [52]CDATA Sections
2.8 [53]Prolog and Document Type Declaration
2.9 [54]Standalone Document Declaration
2.10 [55]White Space Handling
2.11 [56]End-of-Line Handling
2.12 [57]Language Identification
3 [58]Logical Structures
3.1 [59]Start-Tags, End-Tags, and Empty-Element Tags
3.2 [60]Element Type Declarations
3.2.1 [61]Element Content
3.2.2 [62]Mixed Content
3.3 [63]Attribute-List Declarations
3.3.1 [64]Attribute Types
3.3.2 [65]Attribute Defaults
3.3.3 [66]Attribute-Value Normalization
3.4 [67]Conditional Sections
4 [68]Physical Structures
4.1 [69]Character and Entity References
4.2 [70]Entity Declarations
4.2.1 [71]Internal Entities
4.2.2 [72]External Entities
4.3 [73]Parsed Entities
4.3.1 [74]The Text Declaration
4.3.2 [75]Well-Formed Parsed Entities
4.3.3 [76]Character Encoding in Entities
4.4 [77]XML Processor Treatment of Entities and References
4.4.1 [78]Not Recognized
4.4.2 [79]Included
4.4.3 [80]Included If Validating
4.4.4 [81]Forbidden
4.4.5 [82]Included in Literal
4.4.6 [83]Notify
4.4.7 [84]Bypassed
4.4.8 [85]Included as PE
4.4.9 [86]Error
4.5 [87]Construction of Entity Replacement Text
4.6 [88]Predefined Entities
4.7 [89]Notation Declarations
4.8 [90]Document Entity
5 [91]Conformance
5.1 [92]Validating and Non-Validating Processors
5.2 [93]Using XML Processors
6 [94]Notation
Appendices
A [95]References
A.1 [96]Normative References
A.2 [97]Other References
B [98]Character Classes
C [99]XML and SGML (Non-Normative)
D [100]Expansion of Entity and Character References (Non-Normative)
E [101]Deterministic Content Models (Non-Normative)
F [102]Autodetection of Character Encodings (Non-Normative)
F.1 [103]Detection Without External Encoding Information
F.2 [104]Priorities in the Presence of External Encoding Information
G [105]W3C XML Working Group (Non-Normative)
H [106]W3C XML Core Working Group (Non-Normative)
I [107]Production Notes (Non-Normative)
J [108]Suggestions for XML Names (Non-Normative)
____________________________________________________________________________
1 Introduction
Extensible Markup Language, abbreviated XML, describes a class of data objects called
[109]XML documents and partially describes the behavior of computer programs which
process them. XML is an application profile or restricted form of SGML, the Standard
Generalized Markup Language [110][ISO 8879]. By construction, XML documents are
conforming SGML documents.
XML documents are made up of storage units called [111]entities, which contain either
parsed or unparsed data. Parsed data is made up of [112]characters, some of which form
[113]character data, and some of which form [114]markup. Markup encodes a description
of the document's storage layout and logical structure. XML provides a mechanism to
impose constraints on the storage layout and logical structure.
[Definition: A software module called an XML processor is used to read XML documents
and provide access to their content and structure.] [Definition: It is assumed that an
XML processor is doing its work on behalf of another module, called the application.]
This specification describes the required behavior of an XML processor in terms of how
it must read XML data and the information it must provide to the application.
1.1 Origin and Goals
XML was developed by an XML Working Group (originally known as the SGML Editorial
Review Board) formed under the auspices of the World Wide Web Consortium (W3C) in 1996.
It was chaired by Jon Bosak of Sun Microsystems with the active participation of an XML
Special Interest Group (previously known as the SGML Working Group) also organized by
the W3C. The membership of the XML Working Group is given in an appendix. Dan Connolly
served as the Working Group's contact with the W3C.
The design goals for XML are:
1. XML shall be straightforwardly usable over the Internet.
2. XML shall support a wide variety of applications.
3. XML shall be compatible with SGML.
4. It shall be easy to write programs which process XML documents.
5. The number of optional features in XML is to be kept to the absolute minimum,
ideally zero.
6. XML documents should be human-legible and reasonably clear.
7. The XML design should be prepared quickly.
8. The design of XML shall be formal and concise.
9. XML documents shall be easy to create.
10. Terseness in XML markup is of minimal importance.
This specification, together with associated standards (Unicode [115][Unicode]
and ISO/IEC 10646 [116][ISO/IEC 10646] for characters, Internet BCP 47 [117][IETF
BCP 47] and the Language Subtag Registry [118][IANA-LANGCODES] for language
identification tags), provides all the information necessary to understand XML
Version 1.0 and construct computer programs to process it.
This version of the XML specification may be distributed freely, as long as all
text and legal notices remain intact.
1.2 Terminology
The terminology used to describe XML documents is defined in the body of this
specification. The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD
NOT, RECOMMENDED, MAY, and OPTIONAL, when EMPHASIZED, are to be interpreted as
described in [119][IETF RFC 2119]. In addition, the terms defined in the following list
are used in building those definitions and in describing the actions of an XML
processor:
error
[Definition: A violation of the rules of this specification; results are
undefined. Unless otherwise specified, failure to observe a prescription
of this specification indicated by one of the keywords MUST, REQUIRED,
MUST NOT, SHALL and SHALL NOT is an error. Conforming software MAY detect
and report an error and MAY recover from it.]
fatal error
[Definition: An error which a conforming [120]XML processor MUST detect
and report to the application. After encountering a fatal error, the
processor MAY continue processing the data to search for further errors
and MAY report such errors to the application. In order to support
correction of errors, the processor MAY make unprocessed data from the
document (with intermingled character data and markup) available to the
application. Once a fatal error is detected, however, the processor MUST
NOT continue normal processing (i.e., it MUST NOT continue to pass
character data and information about the document's logical structure to
the application in the normal way).]
at user option
[Definition: Conforming software MAY or MUST (depending on the modal verb
in the sentence) behave as described; if it does, it MUST provide users a
means to enable or disable the behavior described.]
validity constraint
[Definition: A rule which applies to all [121]valid XML documents.
Violations of validity constraints are errors; they MUST, at user option,
be reported by [122]validating XML processors.]
well-formedness constraint
[Definition: A rule which applies to all [123]well-formed XML documents.
Violations of well-formedness constraints are [124]fatal errors.]
match
[Definition: (Of strings or names:) Two strings or names being compared
are identical. Characters with multiple possible representations in
ISO/IEC 10646 (e.g. characters with both precomposed and base+diacritic
forms) match only if they have the same representation in both strings. No
case folding is performed. (Of strings and rules in the grammar:) A string
matches a grammatical production if it belongs to the language generated
by that production. (Of content and content models:) An element matches
its declaration when it conforms in the fashion described in the
constraint [VC: [125]Element Valid].]
for compatibility
[Definition: Marks a sentence describing a feature of XML included solely
to ensure that XML remains compatible with SGML.]
for interoperability
[Definition: Marks a sentence describing a non-binding recommendation
included to increase the chances that XML documents can be processed by
the existing installed base of SGML processors which predate the WebSGML
Adaptations Annex to ISO 8879.]
2 Documents
[Definition: A data object is an XML document if it is [126]well-formed, as defined in
this specification. In addition, the XML document is [127]valid if it meets certain
further constraints.]
Each XML document has both a logical and a physical structure. Physically, the document
is composed of units called [128]entities. An entity may [129]refer to other entities
to cause their inclusion in the document. A document begins in a "root" or
[130]document entity. Logically, the document is composed of declarations, elements,
comments, character references, and processing instructions, all of which are indicated
in the document by explicit markup. The logical and physical structures MUST nest
properly, as described in [131]4.3.2 Well-Formed Parsed Entities.
2.1 Well-Formed XML Documents
[Definition: A textual object is a well-formed XML document if:]
1. Taken as a whole, it matches the production labeled [132]document.
2. It meets all the well-formedness constraints given in this specification.
3. Each of the [133]parsed entities which is referenced directly or indirectly
within the document is [134]well-formed.
Document
[1] document ::= [135]prolog [136]element [137]Misc*
Matching the [138]document production implies that:
1. It contains one or more [139]elements.
2. [Definition: There is exactly one element, called the root, or document
element, no part of which appears in the [140]content of any other element.]
For all other elements, if the [141]start-tag is in the content of another
element, the [142]end-tag is in the content of the same element. More simply
stated, the elements, delimited by start- and end-tags, nest properly within
each other.
[Definition: As a consequence of this, for each non-root element C in the
document, there is one other element P in the document such that C is in the
content of P, but is not in the content of any other element that is in the
content of P. P is referred to as the parent of C, and C as a child of P.]
2.2 Characters
[Definition: A parsed entity contains text, a sequence of [143]characters, which may
represent markup or character data.] [Definition: A character is an atomic unit of text
as specified by ISO/IEC 10646:2000 [144][ISO/IEC 10646]. Legal characters are tab,
carriage return, line feed, and the legal characters of Unicode and ISO/IEC 10646. The
versions of these standards cited in [145]A.1 Normative References were current at the
time this document was prepared. New characters may be added to these standards by
amendments or new editions. Consequently, XML processors MUST accept any character in
the range specified for [146]Char. ]
Character Range
[2] Char ::= #x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] |
[#x10000-#x10FFFF] /* any Unicode character, excluding the surrogate blocks,
FFFE, and FFFF. */
The mechanism for encoding character code points into bit patterns may vary from entity
to entity. All XML processors MUST accept the UTF-8 and UTF-16 encodings of Unicode
[147][Unicode]; the mechanisms for signaling which of the two is in use, or for
bringing other encodings into play, are discussed later, in [148]4.3.3 Character
Encoding in Entities.
Note:
Document authors are encouraged to avoid "compatibility characters", as defined
in section 2.3 of [149][Unicode]. The characters defined in the following ranges
are also discouraged. They are either control characters or permanently undefined
Unicode characters:
[#x7F-#x84], [#x86-#x9F], [#xFDD0-#xFDEF],
[#x1FFFE-#x1FFFF], [#x2FFFE-#x2FFFF], [#x3FFFE-#x3FFFF],
[#x4FFFE-#x4FFFF], [#x5FFFE-#x5FFFF], [#x6FFFE-#x6FFFF],
[#x7FFFE-#x7FFFF], [#x8FFFE-#x8FFFF], [#x9FFFE-#x9FFFF],
[#xAFFFE-#xAFFFF], [#xBFFFE-#xBFFFF], [#xCFFFE-#xCFFFF],
[#xDFFFE-#xDFFFF], [#xEFFFE-#xEFFFF], [#xFFFFE-#xFFFFF],
[#x10FFFE-#x10FFFF].
2.3 Common Syntactic Constructs
This section defines some symbols used widely in the grammar.
[150]S (white space) consists of one or more space (#x20) characters, carriage returns,
line feeds, or tabs.
White Space
[3] S ::= (#x20 | #x9 | #xD | #xA)+
Note:
The presence of #xD in the above production is maintained purely for backward
compatibility with the [151]First Edition. As explained in [152]2.11 End-of-Line
Handling, all #xD characters literally present in an XML document are either
removed or replaced by #xA characters before any other processing is done. The
only way to get a #xD character to match this production is to use a character
reference in an entity value literal.
An [153]Nmtoken (name token) is any mixture of name characters.
[Definition: A [154]Name is an [155]Nmtoken with a restricted set of initial
characters.] Disallowed initial characters for [156]Names include digits, diacritics,
the full stop and the hyphen.
Names beginning with the string "xml", or with any string which would match (('X'|'x')
('M'|'m') ('L'|'l')), are reserved for standardization in this or future versions of
this specification.
Note:
The Namespaces in XML Recommendation [157][XML Names] assigns a meaning to names
containing colon characters. Therefore, authors should not use the colon in XML
names except for namespace purposes, but XML processors must accept the colon as
a name character.
The first character of a [158]Name MUST be a [159]NameStartChar, and any other
characters MUST be [160]NameChars; this mechanism is used to prevent names from
beginning with European (ASCII) digits or with basic combining characters. Almost
all characters are permitted in names, except those which either are or
reasonably could be used as delimiters. The intention is to be inclusive rather
than exclusive, so that writing systems not yet encoded in Unicode can be used in
XML names. See [161]J Suggestions for XML Names for suggestions on the creation
of names.
Document authors are encouraged to use names which are meaningful words or
combinations of words in natural languages, and to avoid symbolic or white space
characters in names. Note that COLON, HYPHEN-MINUS, FULL STOP (period), LOW LINE
(underscore), and MIDDLE DOT are explicitly permitted.
The ASCII symbols and punctuation marks, along with a fairly large group of
Unicode symbol characters, are excluded from names because they are more useful
as delimiters in contexts where XML names are used outside XML documents;
providing this group gives those contexts hard guarantees about what cannot be
part of an XML name. The character #x037E, GREEK QUESTION MARK, is excluded
because when normalized it becomes a semicolon, which could change the meaning of
entity references.
Names and Tokens
[4] NameStartChar ::= ":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] |
[#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] | [#x200C-#x200D] |
[#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] | [#xF900-#xFDCF] |
[#xFDF0-#xFFFD] | [#x10000-#xEFFFF]
[4a] NameChar ::= [162]NameStartChar | "-" | "". | [0-9] | #xB7 |
[#x0300-#x036F] | [#x203F-#x2040]
[5] Name ::= [163]NameStartChar ([164]NameChar)*
[6] Names ::= [165]Name (#x20 [166]Name)*
[7] Nmtoken ::= ([167]NameChar)+
[8] Nmtokens ::= [168]Nmtoken (#x20 [169]Nmtoken)*
Note:
The [170]Names and [171]Nmtokens productions are used to define the validity of
tokenized attribute values after normalization (see [172]3.3.1 Attribute Types).
Literal data is any quoted string not containing the quotation mark used as a
delimiter for that string. Literals are used for specifying the content of
internal entities ([173]EntityValue), the values of attributes ([174]AttValue),
and external identifiers ([175]SystemLiteral). Note that a [176]SystemLiteral can
be parsed without scanning for markup.
Literals
[9] EntityValue ::= '"' ([^%&"] | [177]PEReference | [178]Reference)*
'"'
| "'" ([^%&'] | [179]PEReference | [180]Reference)* "'"
[10] AttValue ::= '"' ([^) may be represented
using the string " > ", and MUST, [204]for compatibility, be escaped using either "
> " or a character reference when it appears in the string " ]]> " in content, when
that string is not marking the end of a [205]CDATA section.
In the content of elements, character data is any string of characters which does not
contain the start-delimiter of any markup and does not include the CDATA-section-close
delimiter, " ]]> ". In a CDATA section, character data is any string of characters not
including the CDATA-section-close delimiter, " ]]> ".
To allow attribute values to contain both single and double quotes, the apostrophe or
single-quote character (') may be represented as " ' ", and the double-quote
character (") as " " ".
Character Data
[14] CharData ::= [^
Note that the grammar does not allow a comment ending in --->. The following
example is not well-formed.
2.6 Processing Instructions
[Definition: Processing instructions (PIs) allow documents to contain instructions for
applications.]
Processing Instructions
[16] PI ::= ''
[215]Char*)))? '?>'
[17] PITarget ::= [216]Name - (('X' | 'x') ('M' | 'm') ('L' | 'l'))
PIs are not part of the document's [217]character data, but MUST be passed through to
the application. The PI begins with a target ([218]PITarget) used to identify the
application to which the instruction is directed. The target names " XML ", " xml ",
and so on are reserved for standardization in this or future versions of this
specification. The XML [219]Notation mechanism may be used for formal declaration of PI
targets. Parameter entity references MUST NOT be recognized within processing
instructions.
2.7 CDATA Sections
[Definition: CDATA sections may occur anywhere character data may occur; they are used
to escape blocks of text containing characters which would otherwise be recognized as
markup. CDATA sections begin with the string " ":]
CDATA Sections
[18] CDSect ::= [220]CDStart [221]CData [222]CDEnd
[19] CDStart ::= '' [225]Char*))
[21] CDEnd ::= ']]>'
Within a CDATA section, only the [226]CDEnd string is recognized as markup, so that
left angle brackets and ampersands may occur in their literal form; they need not (and
cannot) be escaped using " < " and " & ". CDATA sections cannot nest.
An example of a CDATA section, in which " " and " " are
recognized as [227]character data, not [228]markup:
Hello, world!]]>
2.8 Prolog and Document Type Declaration
[Definition: XML documents SHOULD begin with an XML declaration which specifies the
version of XML being used.] For example, the following is a complete XML document,
[229]well-formed but not [230]valid:
Hello, world!
and so is this:
Hello, world!
The function of the markup in an XML document is to describe its storage and
logical structure and to associate attribute name-value pairs with its logical
structures. XML provides a mechanism, the [231]document type declaration, to
define constraints on the logical structure and to support the use of predefined
storage units. [Definition: An XML document is valid if it has an associated
document type declaration and if the document complies with the constraints
expressed in it.]
The document type declaration MUST appear before the first [232]element in the
document.
Prolog
[22] prolog ::= [233]XMLDecl? [234]Misc* ([235]doctypedecl [236]Misc*)?
[23] XMLDecl ::= ''
[24] VersionInfo ::= [241]S 'version' [242]Eq ("'" [243]VersionNum "'" |
'"' [244]VersionNum '"')
[25] Eq ::= [245]S? '=' [246]S?
[26] VersionNum ::= '1.' [0-9]+
[27] Misc ::= [247]Comment | [248]PI | [249]S
Even though the [250]VersionNum production matches any version number of the form
'1.x', XML 1.0 documents SHOULD NOT specify a version number other than '1.0'.
Note:
When an XML 1.0 processor encounters a document that specifies a 1.x version
number other than '1.0', it will process it as a 1.0 document. This means that an
XML 1.0 processor will accept 1.x documents provided they do not use any non-1.0
features.
[Definition: The XML document type declaration contains or points to [251]markup
declarations that provide a grammar for a class of documents. This grammar is
known as a document type definition, or DTD. The document type declaration can
point to an external subset (a special kind of [252]external entity) containing
markup declarations, or can contain the markup declarations directly in an
internal subset, or can do both. The DTD for a document consists of both subsets
taken together.]
[Definition: A markup declaration is an [253]element type declaration, an
[254]attribute-list declaration, an [255]entity declaration, or a [256]notation
declaration.] These declarations may be contained in whole or in part within
[257]parameter entities, as described in the well-formedness and validity
constraints below. For further information, see [258]4 Physical Structures.
Document Type Definition
[28] doctypedecl ::= '' [266][VC: Root
Element Type]
[267][WFC: External Subset]
[28a] DeclSep ::= [268]PEReference | [269]S [270][WFC: PE Between
Declarations]
[28b] intSubset ::= ([271]markupdecl | [272]DeclSep)*
[29] markupdecl ::= [273]elementdecl | [274]AttlistDecl |
[275]EntityDecl | [276]NotationDecl | [277]PI | [278]Comment [279][VC: Proper
Declaration/PE Nesting]
[280][WFC: PEs in Internal Subset]
Note that it is possible to construct a well-formed document containing a
[281]doctypedecl that neither points to an external subset nor contains an
internal subset.
The markup declarations may be made up in whole or in part of the
[282]replacement text of [283]parameter entities. The productions later in this
specification for individual nonterminals ([284]elementdecl, [285]AttlistDecl,
and so on) describe the declarations after all the parameter entities have been
[286]included.
Parameter entity references are recognized anywhere in the DTD (internal and
external subsets and external parameter entities), except in literals, processing
instructions, comments, and the contents of ignored conditional sections (see
[287]3.4 Conditional Sections). They are also recognized in entity value
literals. The use of parameter entities in the internal subset is restricted as
described below.
Validity constraint: Root Element Type
The [288]Name in the document type declaration MUST match the element type of the
[289]root element.
Validity constraint: Proper Declaration/PE Nesting
Parameter-entity [290]replacement text MUST be properly nested with markup
declarations. That is to say, if either the first character or the last character
of a markup declaration ([291]markupdecl above) is contained in the replacement
text for a [292]parameter-entity reference, both MUST be contained in the same
replacement text.
Well-formedness constraint: PEs in Internal Subset
In the internal DTD subset, [293]parameter-entity references MUST NOT occur
within markup declarations; they may occur where markup declarations can occur.
(This does not apply to references that occur in external parameter entities or
to the external subset.)
Well-formedness constraint: External Subset
The external subset, if any, MUST match the production for [294]extSubset.
Well-formedness constraint: PE Between Declarations
The replacement text of a parameter entity reference in a [295]DeclSep MUST match
the production [296]extSubsetDecl.
Like the internal subset, the external subset and any external parameter entities
referenced in a [297]DeclSep MUST consist of a series of complete markup
declarations of the types allowed by the non-terminal symbol [298]markupdecl,
interspersed with white space or [299]parameter-entity references. However,
portions of the contents of the external subset or of these external parameter
entities may conditionally be ignored by using the [300]conditional section
construct; this is not allowed in the internal subset but is allowed in external
parameter entities referenced in the internal subset.
External Subset
[30] extSubset ::= [301]TextDecl? [302]extSubsetDecl
[31] extSubsetDecl ::= ( [303]markupdecl | [304]conditionalSect |
[305]DeclSep)*
The external subset and external parameter entities also differ from the internal
subset in that in them, [306]parameter-entity references are permitted within
markup declarations, not only between markup declarations.
An example of an XML document with a document type declaration:
Hello, world!
The [307]system identifier " hello.dtd " gives the address (a URI reference) of a
DTD for the document.
The declarations can also be given locally, as in this example:
Hello, world!
If both the external and internal subsets are used, the internal subset MUST be
considered to occur before the external subset. This has the effect that entity
and attribute-list declarations in the internal subset take precedence over those
in the external subset.
2.9 Standalone Document Declaration
Markup declarations can affect the content of the document, as passed from an [308]XML
processor to an application; examples are attribute defaults and entity declarations.
The standalone document declaration, which may appear as a component of the XML
declaration, signals whether or not there are such declarations which appear external
to the [309]document entity or in parameter entities. [Definition: An external markup
declaration is defined as a markup declaration occurring in the external subset or in a
parameter entity (external or internal, the latter being included because
non-validating processors are not required to read them).]
Standalone Document Declaration
[32] SDDecl ::= [310]S 'standalone' [311]Eq (("'" ('yes' | 'no') "'") |
('"' ('yes' | 'no') '"')) [312][VC: Standalone Document Declaration]
In a standalone document declaration, the value "yes" indicates that there are no
[313]external markup declarations which affect the information passed from the XML
processor to the application. The value "no" indicates that there are or may be such
external markup declarations. Note that the standalone document declaration only
denotes the presence of external declarations; the presence, in a document, of
references to external entities, when those entities are internally declared, does not
change its standalone status.
If there are no external markup declarations, the standalone document declaration has
no meaning. If there are external markup declarations but there is no standalone
document declaration, the value "no" is assumed.
Any XML document for which standalone="no" holds can be converted algorithmically to a
standalone document, which may be desirable for some network delivery applications.
Validity constraint: Standalone Document Declaration
The standalone document declaration MUST have the value "no" if any external
markup declarations contain declarations of:
* attributes with [314]default values, if elements to which these attributes
apply appear in the document without specifications of values for these
attributes, or
* entities (other than amp, lt, gt, apos, quot), if [315]references to those
entities appear in the document, or
* attributes with tokenized types, where the attribute appears in the document
with a value such that [316]normalization will produce a different value from
that which would be produced in the absence of the declaration, or
* element types with [317]element content, if white space occurs directly
within any instance of those types.
An example XML declaration with a standalone document declaration:
2.10 White Space Handling
In editing XML documents, it is often convenient to use "white space" (spaces, tabs,
and blank lines) to set apart the markup for greater readability. Such white space is
typically not intended for inclusion in the delivered version of the document. On the
other hand, "significant" white space that should be preserved in the delivered version
is common, for example in poetry and source code.
An [318]XML processor MUST always pass all characters in a document that are not markup
through to the application. A [319]validating XML processor MUST also inform the
application which of these characters constitute white space appearing in [320]element
content.
A special [321]attribute named xml:space may be attached to an element to signal an
intention that in that element, white space should be preserved by applications. In
valid documents, this attribute, like any other, MUST be [322]declared if it is used.
When declared, it MUST be given as an [323]enumerated type whose values are one or both
of "default" and "preserve". For example:
The value "default" signals that applications' default white-space processing
modes are acceptable for this element; the value "preserve" indicates the intent
that applications preserve all the white space. This declared intent is
considered to apply to all elements within the content of the element where it is
specified, unless overridden with another instance of the xml:space attribute.
This specification does not give meaning to any value of xml:space other than
"default" and "preserve". It is an error for other values to be specified; the
XML processor MAY report the error or MAY recover by ignoring the attribute
specification or by reporting the (erroneous) value to the application.
Applications may ignore or reject erroneous values.
The [324]root element of any document is considered to have signaled no
intentions as regards application space handling, unless it provides a value for
this attribute or the attribute is declared with a default value.
2.11 End-of-Line Handling
XML [325]parsed entities are often stored in computer files which, for editing
convenience, are organized into lines. These lines are typically separated by some
combination of the characters CARRIAGE RETURN (#xD) and LINE FEED (#xA).
To simplify the tasks of [326]applications, the [327]XML processor MUST behave as if it
normalized all line breaks in external parsed entities (including the document entity)
on input, before parsing, by translating both the two-character sequence #xD #xA and
any #xD that is not followed by #xA to a single #xA character.
2.12 Language Identification
In document processing, it is often useful to identify the natural or formal language
in which the content is written. A special [328]attribute named xml:lang may be
inserted in documents to specify the language used in the contents and attribute values
of any element in an XML document. In valid documents, this attribute, like any other,
MUST be [329]declared if it is used. The values of the attribute are language
identifiers as defined by [330][IETF BCP 47], Tags for the Identification of Languages;
in addition, the empty string may be specified.
(Productions 33 through 38 have been removed.)
For example:
The quick brown fox jumps over the lazy dog.
What colour is it?
What color is it?
Habe nun, ach! Philosophie,
Juristerei, und Medizin
und leider auch Theologie
durchaus studiert mit heißem Bemüh'n.
The language specified by xml:lang applies to the element where it is specified
(including the values of its attributes), and to all elements in its content
unless overridden with another instance of xml:lang. In particular, the empty
value of xml:lang is used on an element B to override a specification of xml:lang
on an enclosing element A, without specifying another language. Within B, it is
considered that there is no language information available, just as if xml:lang
had not been specified on B or any of its ancestors. Applications determine which
of an element's attribute values and which parts of its character content, if
any, are treated as language-dependent values described by xml:lang.
Note:
Language information may also be provided by external transport protocols (e.g.
HTTP or MIME). When available, this information may be used by XML applications,
but the more local information provided by xml:lang should be considered to
override it.
A simple declaration for xml:lang might take the form
xml:lang CDATA #IMPLIED
but specific default values may also be given, if appropriate. In a collection of
French poems for English students, with glosses and notes in English, the
xml:lang attribute might be declared this way:
3 Logical Structures
[Definition: Each [331]XML document contains one or more elements, the boundaries of
which are either delimited by [332]start-tags and [333]end-tags, or, for [334]empty
elements, by an [335]empty-element tag. Each element has a type, identified by name,
sometimes called its "generic identifier" (GI), and may have a set of attribute
specifications.] Each attribute specification has a [336]name and a [337]value.
Element
[39] element ::= [338]EmptyElemTag
| [339]STag [340]content [341]ETag [342][WFC: Element Type Match]
[343][VC: Element Valid]
This specification does not constrain the application semantics, use, or (beyond
syntax) names of the element types and attributes, except that names beginning with a
match to (('X'|'x')('M'|'m')('L'|'l')) are reserved for standardization in this or
future versions of this specification.
Well-formedness constraint: Element Type Match
The [344]Name in an element's end-tag MUST match the element type in the
start-tag.
Validity constraint: Element Valid
An element is valid if there is a declaration matching [345]elementdecl where the
[346]Name matches the element type, and one of the following holds:
1. The declaration matches EMPTY and the element has no [347]content (not even
entity references, comments, PIs or white space).
2. The declaration matches [348]children and the sequence of [349]child elements
belongs to the language generated by the regular expression in the content
model, with optional white space, comments and PIs (i.e. markup matching
production [27] [350]Misc) between the start-tag and the first child element,
between child elements, or between the last child element and the end-tag.
Note that a CDATA section containing only white space or a reference to an
entity whose replacement text is character references expanding to white
space do not match the nonterminal [351]S, and hence cannot appear in these
positions; however, a reference to an internal entity with a literal value
consisting of character references expanding to white space does match
[352]S, since its replacement text is the white space resulting from
expansion of the character references.
3. The declaration matches [353]Mixed, and the content (after replacing any
entity references with their replacement text) consists of [354]character
data (including [355]CDATA sections), [356]comments, [357]PIs and [358]child
elements whose types match names in the content model.
4. The declaration matches ANY, and the content (after replacing any entity
references with their replacement text) consists of character data,
[359]CDATA sections, [360]comments, [361]PIs and [362]child elements whose
types have been declared.
3.1 Start-Tags, End-Tags, and Empty-Element Tags
[Definition: The beginning of every non-empty XML element is marked by a start-tag.]
Start-tag
[40] STag ::= ''
[367][WFC: Unique Att Spec]
[41] Attribute ::= [368]Name [369]Eq [370]AttValue [371][VC: Attribute
Value Type]
[372][WFC: No External Entity References]
[373][WFC: No < in Attribute Values]
The [374]Name in the start- and end-tags gives the element's type. [Definition: The
[375]Name-[376]AttValue pairs are referred to as the attribute specifications of the
element], [Definition: with the [377]Name in each pair referred to as the attribute
name ] and [Definition: the content of the [378]AttValue (the text between the ' or "
delimiters) as the attribute value.] Note that the order of attribute specifications in
a start-tag or empty-element tag is not significant.
Well-formedness constraint: Unique Att Spec
An attribute name MUST NOT appear more than once in the same start-tag or
empty-element tag.
Validity constraint: Attribute Value Type
The attribute MUST have been declared; the value MUST be of the type declared for
it. (For attribute types, see [379]3.3 Attribute-List Declarations.)
Well-formedness constraint: No External Entity References
Attribute values MUST NOT contain direct or indirect entity references to
external entities.
Well-formedness constraint: No < in Attribute Values
The [380]replacement text of any entity referred to directly or indirectly in an
attribute value MUST NOT contain a '
[53] AttDef ::= [472]S [473]Name [474]S [475]AttType [476]S
[477]DefaultDecl
The [478]Name in the [479]AttlistDecl rule is the type of an element. At user
option, an XML processor MAY issue a warning if attributes are declared for an
element type not itself declared, but this is not an error. The [480]Name in the
[481]AttDef rule is the name of the attribute.
When more than one [482]AttlistDecl is provided for a given element type, the
contents of all those provided are merged. When more than one definition is
provided for the same attribute of a given element type, the first declaration is
binding and later declarations are ignored. [483]For interoperability, writers of
DTDs may choose to provide at most one attribute-list declaration for a given
element type, at most one attribute definition for a given attribute name in an
attribute-list declaration, and at least one attribute definition in each
attribute-list declaration. For interoperability, an XML processor MAY at user
option issue a warning when more than one attribute-list declaration is provided
for a given element type, or more than one attribute definition is provided for a
given attribute, but this is not an error.
3.3.1 Attribute Types
XML attribute types are of three kinds: a string type, a set of tokenized types, and
enumerated types. The string type may take any literal string as a value; the tokenized
types are more constrained. The validity constraints noted in the grammar are applied
after the attribute value has been normalized as described in [484]3.3.3
Attribute-Value Normalization.
Attribute Types
[54] AttType ::= [485]StringType | [486]TokenizedType |
[487]EnumeratedType
[55] StringType ::= 'CDATA'
[56] TokenizedType ::= 'ID' [488][VC: ID]
[489][VC: One ID per Element Type]
[490][VC: ID Attribute Default]
| 'IDREF' [491][VC: IDREF]
| 'IDREFS' [492][VC: IDREF]
| 'ENTITY' [493][VC: Entity Name]
| 'ENTITIES' [494][VC: Entity Name]
| 'NMTOKEN' [495][VC: Name Token]
| 'NMTOKENS' [496][VC: Name Token]
Validity constraint: ID
Values of type ID MUST match the [497]Name production. A name MUST NOT appear
more than once in an XML document as a value of this type; i.e., ID values MUST
uniquely identify the elements which bear them.
Validity constraint: One ID per Element Type
An element type MUST NOT have more than one ID attribute specified.
Validity constraint: ID Attribute Default
An ID attribute MUST have a declared default of #IMPLIED or #REQUIRED.
Validity constraint: IDREF
Values of type IDREF MUST match the [498]Name production, and values of type
IDREFS MUST match [499]Names; each [500]Name MUST match the value of an ID
attribute on some element in the XML document; i.e. IDREF values MUST match the
value of some ID attribute.
Validity constraint: Entity Name
Values of type ENTITY MUST match the [501]Name production, values of type
ENTITIES MUST match [502]Names; each [503]Name MUST match the name of an
[504]unparsed entity declared in the [505]DTD.
Validity constraint: Name Token
Values of type NMTOKEN MUST match the [506]Nmtoken production; values of type
NMTOKENS MUST match [507]Nmtokens.
[Definition: Enumerated attributes have a list of allowed values in their
declaration ]. They MUST take one of those values. There are two kinds of
enumerated attribute types:
Enumerated Attribute Types
[57] EnumeratedType ::= [508]NotationType | [509]Enumeration
[58] NotationType ::= 'NOTATION' [510]S '(' [511]S? [512]Name ([513]S?
'|' [514]S? [515]Name)* [516]S? ')' [517][VC: Notation Attributes]
[518][VC: One Notation Per Element Type]
[519][VC: No Notation on Empty Element]
[520][VC: No Duplicate Tokens]
[59] Enumeration ::= '(' [521]S? [522]Nmtoken ([523]S? '|' [524]S?
[525]Nmtoken)* [526]S? ')' [527][VC: Enumeration]
[528][VC: No Duplicate Tokens]
A NOTATION attribute identifies a [529]notation, declared in the DTD with
associated system and/or public identifiers, to be used in interpreting the
element to which the attribute is attached.
Validity constraint: Notation Attributes
Values of this type MUST match one of the [530]notation names included in the
declaration; all notation names in the declaration MUST be declared.
Validity constraint: One Notation Per Element Type
An element type MUST NOT have more than one NOTATION attribute specified.
Validity constraint: No Notation on Empty Element
[531]For compatibility, an attribute of type NOTATION MUST NOT be declared on an
element declared EMPTY.
Validity constraint: No Duplicate Tokens
The notation names in a single [532]NotationType attribute declaration, as well
as the [533]NmTokens in a single [534]Enumeration attribute declaration, MUST all
be distinct.
Validity constraint: Enumeration
Values of this type MUST match one of the [535]Nmtoken tokens in the declaration.
[536]For interoperability, the same [537]Nmtoken SHOULD NOT occur more than once
in the enumerated attribute types of a single element type.
3.3.2 Attribute Defaults
An [538]attribute declaration provides information on whether the attribute's presence
is REQUIRED, and if not, how an XML processor is to react if a declared attribute is
absent in a document.
Attribute Defaults
[60] DefaultDecl ::= '#REQUIRED' | '#IMPLIED'
| (('#FIXED' [539]S)? [540]AttValue) [541][VC: Required Attribute]
[542][VC: Attribute Default Value Syntactically Correct]
[543][WFC: No < in Attribute Values]
[544][VC: Fixed Attribute Default]
[545][WFC: No External Entity References]
In an attribute declaration, #REQUIRED means that the attribute MUST always be
provided, #IMPLIED that no default value is provided. [Definition: If the declaration
is neither #REQUIRED nor #IMPLIED, then the [546]AttValue value contains the declared
default value; the #FIXED keyword states that the attribute MUST always have the
default value. When an XML processor encounters an element without a specification for
an attribute for which it has read a default value declaration, it MUST report the
attribute with the declared default value to the application.]
Validity constraint: Required Attribute
If the default declaration is the keyword #REQUIRED, then the attribute MUST be
specified for all elements of the type in the attribute-list declaration.
Validity constraint: Attribute Default Value Syntactically Correct
The declared default value MUST meet the syntactic constraints of the declared
attribute type. That is, the default value of an attribute:
* of type IDREF or ENTITY must match the [547]Name production;
* of type IDREFS or ENTITIES must match the [548]Names production;
* of type NMTOKEN must match the [549]Nmtoken production;
* of type NMTOKENS must match the [550]Nmtokens production;
* of an [551]enumerated type (either a [552]NOTATION type or an
[553]enumeration) must match one of the enumerated values.
Note that only the syntactic constraints of the type are required here; other
constraints (e.g. that the value be the name of a declared unparsed entity, for
an attribute of type ENTITY) will be reported by a validating parser only if an
element without a specification for this attribute actually occurs.
Validity constraint: Fixed Attribute Default
If an attribute has a default value declared with the #FIXED keyword, instances
of that attribute MUST match the default value.
Examples of attribute-list declarations:
3.3.3 Attribute-Value Normalization
Before the value of an attribute is passed to the application or checked for validity,
the XML processor MUST normalize the attribute value by applying the algorithm below,
or by using some other method such that the value passed to the application is the same
as that produced by the algorithm.
1. All line breaks MUST have been normalized on input to #xA as described in
[554]2.11 End-of-Line Handling, so the rest of this algorithm operates on
text normalized in this way.
2. Begin with a normalized value consisting of the empty string.
3. For each character, entity reference, or character reference in the
unnormalized attribute value, beginning with the first and continuing to the
last, do the following:
+ For a character reference, append the referenced character to the
normalized value.
+ For an entity reference, recursively apply step 3 of this algorithm to
the replacement text of the entity.
+ For a white space character (#x20, #xD, #xA, #x9), append a space
character (#x20) to the normalized value.
+ For another character, append the character to the normalized value.
If the attribute type is not CDATA, then the XML processor MUST further process
the normalized attribute value by discarding any leading and trailing space
(#x20) characters, and by replacing sequences of space (#x20) characters by a
single space (#x20) character.
Note that if the unnormalized attribute value contains a character reference to a
white space character other than space (#x20), the normalized value contains the
referenced character itself (#xD, #xA or #x9). This contrasts with the case where
the unnormalized value contains a white space character (not a reference), which
is replaced with a space character (#x20) in the normalized value and also
contrasts with the case where the unnormalized value contains an entity reference
whose replacement text contains a white space character; being recursively
processed, the white space character is replaced with a space character (#x20) in
the normalized value.
All attributes for which no declaration has been read SHOULD be treated by a
non-validating processor as if declared CDATA.
It is an error if an [555]attribute value contains a [556]reference to an entity
for which no declaration has been read.
Following are examples of attribute normalization. Given the following
declarations:
the attribute specifications in the left column below would be normalized to the
character sequences of the middle column if the attribute a is declared NMTOKENS
and to those of the right columns if a is declared CDATA.
Attribute specification a is NMTOKENS a is CDATA
a="
xyz"
x y z
#x20 #x20 x y z
a="&d;&d;A&a; &a;B&da;"
A #x20 B
#x20 #x20 A #x20 #x20 #x20 B #x20 #x20
a=
"

A

B
"
#xD #xD A #xA #xA B #xD #xA
#xD #xD A #xA #xA B #xD #xA
Note that the last example is invalid (but well-formed) if a is declared to be of
type NMTOKENS.
3.4 Conditional Sections
[Definition: Conditional sections are portions of the [557]document type declaration
external subset or of external parameter entities which are included in, or excluded
from, the logical structure of the DTD based on the keyword which governs them.]
Conditional Section
[61] conditionalSect ::= [558]includeSect | [559]ignoreSect
[62] includeSect ::= '' [563][VC: Proper Conditional Section/PE Nesting]
[63] ignoreSect ::= '' [567][VC: Proper Conditional Section/PE Nesting]
[64] ignoreSectContents ::= [568]Ignore ('' [570]Ignore)*
[65] Ignore ::= [571]Char* - ([572]Char* ('') [573]Char*)
Validity constraint: Proper Conditional Section/PE Nesting
If any of the "" of a conditional section is contained in the
replacement text for a parameter-entity reference, all of them MUST be contained
in the same replacement text.
Like the internal and external DTD subsets, a conditional section may contain one or
more complete declarations, comments, processing instructions, or nested conditional
sections, intermingled with white space.
If the keyword of the conditional section is INCLUDE, then the contents of the
conditional section MUST be processed as part of the DTD. If the keyword of the
conditional section is IGNORE, then the contents of the conditional section MUST NOT be
processed as part of the DTD. If a conditional section with a keyword of INCLUDE occurs
within a larger conditional section with a keyword of IGNORE, both the outer and the
inner conditional sections MUST be ignored. The contents of an ignored conditional
section MUST be parsed by ignoring all characters after the "[" following the keyword,
except conditional section starts "", until the matching conditional
section end is found. Parameter entity references MUST NOT be recognized in this
process.
If the keyword of the conditional section is a parameter-entity reference, the
parameter entity MUST be replaced by its content before the processor decides whether
to include or ignore the conditional section.
An example:
]]>
]]>
4 Physical Structures
[Definition: An XML document may consist of one or many storage units. These are called
entities; they all have content and are all (except for the [574]document entity and
the [575]external DTD subset) identified by entity name.] Each XML document has one
entity called the [576]document entity, which serves as the starting point for the
[577]XML processor and may contain the whole document.
Entities may be either parsed or unparsed. [Definition: The contents of a parsed entity
are referred to as its [578]replacement text; this [579]text is considered an integral
part of the document.]
[Definition: An unparsed entity is a resource whose contents may or may not be
[580]text, and if text, may be other than XML. Each unparsed entity has an associated
[581]notation, identified by name. Beyond a requirement that an XML processor make the
identifiers for the entity and notation available to the application, XML places no
constraints on the contents of unparsed entities.]
Parsed entities are invoked by name using entity references; unparsed entities by name,
given in the value of ENTITY or ENTITIES attributes.
[Definition: General entities are entities for use within the document content. In this
specification, general entities are sometimes referred to with the unqualified term
entity when this leads to no ambiguity.] [Definition: Parameter entities are parsed
entities for use within the DTD.] These two types of entities use different forms of
reference and are recognized in different contexts. Furthermore, they occupy different
namespaces; a parameter entity and a general entity with the same name are two distinct
entities.
4.1 Character and Entity References
[Definition: A character reference refers to a specific character in the ISO/IEC 10646
character set, for example one not directly accessible from available input devices.]
Character Reference
[66] CharRef ::= '&#' [0-9]+ ';'
| '&#x' [0-9a-fA-F]+ ';' [582][WFC: Legal Character]
Well-formedness constraint: Legal Character
Characters referred to using character references MUST match the production for
[583]Char.
If the character reference begins with " &#x ", the digits and letters up to the
terminating ; provide a hexadecimal representation of the character's code point in
ISO/IEC 10646. If it begins just with " &# ", the digits up to the terminating ;
provide a decimal representation of the character's code point.
[Definition: An entity reference refers to the content of a named entity.] [Definition:
References to parsed general entities use ampersand (&) and semicolon (;) as
delimiters.] [Definition: Parameter-entity references use percent-sign (%) and
semicolon (;) as delimiters.]
Entity Reference
[67] Reference ::= [584]EntityRef | [585]CharRef
[68] EntityRef ::= '&' [586]Name ';' [587][WFC: Entity Declared]
[588][VC: Entity Declared]
[589][WFC: Parsed Entity]
[590][WFC: No Recursion]
[69] PEReference ::= '%' [591]Name ';' [592][VC: Entity Declared]
[593][WFC: No Recursion]
[594][WFC: In DTD]
Well-formedness constraint: Entity Declared
In a document without any DTD, a document with only an internal DTD subset which
contains no parameter entity references, or a document with " standalone='yes' ",
for an entity reference that does not occur within the external subset or a
parameter entity, the [595]Name given in the entity reference MUST [596]match
that in an [597]entity declaration that does not occur within the external subset
or a parameter entity, except that well-formed documents need not declare any of
the following entities: amp, lt, gt, apos, quot. The declaration of a general
entity MUST precede any reference to it which appears in a default value in an
attribute-list declaration.
Note that non-validating processors are [598]not obligated to read and process
entity declarations occurring in parameter entities or in the external subset;
for such documents, the rule that an entity must be declared is a well-formedness
constraint only if [599]standalone='yes'.
Validity constraint: Entity Declared
In a document with an external subset or parameter entity references, if the
document is not standalone (either "standalone='no'" is specified or there is no
standalone declaration), then the [600]Name given in the entity reference MUST
[601]match that in an [602]entity declaration. For interoperability, valid
documents SHOULD declare the entities amp, lt, gt, apos, quot, in the form
specified in [603]4.6 Predefined Entities. The declaration of a parameter entity
MUST precede any reference to it. Similarly, the declaration of a general entity
MUST precede any attribute-list declaration containing a default value with a
direct or indirect reference to that general entity.
Well-formedness constraint: Parsed Entity
An entity reference MUST NOT contain the name of an [604]unparsed entity.
Unparsed entities may be referred to only in [605]attribute values declared to be
of type ENTITY or ENTITIES.
Well-formedness constraint: No Recursion
A parsed entity MUST NOT contain a recursive reference to itself, either directly
or indirectly.
Well-formedness constraint: In DTD
Parameter-entity references MUST NOT appear outside the [606]DTD.
Examples of character and entity references:
Type less-than (<) to save options.
This document was prepared on &docdate; and
is classified &security-level;.
Example of a parameter-entity reference:
%ISOLat2;
4.2 Entity Declarations
[Definition: Entities are declared thus:]
Entity Declaration
[70] EntityDecl ::= [607]GEDecl | [608]PEDecl
[71] GEDecl ::= ''
[72] PEDecl ::= ''
[73] EntityDef ::= [620]EntityValue | ([621]ExternalID [622]NDataDecl?)
[74] PEDef ::= [623]EntityValue | [624]ExternalID
The [625]Name identifies the entity in an [626]entity reference or, in the case of an
unparsed entity, in the value of an ENTITY or ENTITIES attribute. If the same entity is
declared more than once, the first declaration encountered is binding; at user option,
an XML processor MAY issue a warning if entities are declared multiple times.
4.2.1 Internal Entities
[Definition: If the entity definition is an [627]EntityValue, the defined entity is
called an internal entity. There is no separate physical storage object, and the
content of the entity is given in the declaration.] Note that some processing of entity
and character references in the [628]literal entity value may be required to produce
the correct [629]replacement text: see [630]4.5 Construction of Entity Replacement
Text.
An internal entity is a [631]parsed entity.
Example of an internal entity declaration:
4.2.2 External Entities
[Definition: If the entity is not internal, it is an external entity, declared as
follows:]
External Entity Declaration
[75] ExternalID ::= 'SYSTEM' [632]S [633]SystemLiteral
| 'PUBLIC' [634]S [635]PubidLiteral [636]S [637]SystemLiteral
[76] NDataDecl ::= [638]S 'NDATA' [639]S [640]Name [641][VC: Notation
Declared]
If the [642]NDataDecl is present, this is a general [643]unparsed entity; otherwise it
is a parsed entity.
Validity constraint: Notation Declared
The [644]Name MUST match the declared name of a [645]notation.
[Definition: The [646]SystemLiteral is called the entity's system identifier. It
is meant to be converted to a URI reference (as defined in [647][IETF RFC 3986]),
as part of the process of dereferencing it to obtain input for the XML processor
to construct the entity's replacement text.] It is an error for a fragment
identifier (beginning with a # character) to be part of a system identifier.
Unless otherwise provided by information outside the scope of this specification
(e.g. a special XML element type defined by a particular DTD, or a processing
instruction defined by a particular application specification), relative URIs are
relative to the location of the resource within which the entity declaration
occurs. This is defined to be the external entity containing the '
4.4.6 Notify
When the name of an [744]unparsed entity appears as a token in the value of an
attribute of declared type ENTITY or ENTITIES, a validating processor MUST inform the
application of the [745]system and [746]public (if any) identifiers for both the entity
and its associated [747]notation.
4.4.7 Bypassed
When a general entity reference appears in the [748]EntityValue in an entity
declaration, it MUST be bypassed and left as is.
4.4.8 Included as PE
Just as with external parsed entities, parameter entities need only be [749]included if
validating. When a parameter-entity reference is recognized in the DTD and included,
its [750]replacement text MUST be enlarged by the attachment of one leading and one
following space (#x20) character; the intent is to constrain the replacement text of
parameter entities to contain an integral number of grammatical tokens in the DTD. This
behavior MUST NOT apply to parameter entity references within entity values; these are
described in [751]4.4.5 Included in Literal.
4.4.9 Error
It is an [752]error for a reference to an unparsed entity to appear in the
[753]EntityValue in an entity declaration.
4.5 Construction of Entity Replacement Text
In discussing the treatment of entities, it is useful to distinguish two forms of the
entity's value. [Definition: For an internal entity, the literal entity value is the
quoted string actually present in the entity declaration, corresponding to the
non-terminal [754]EntityValue.] [Definition: For an external entity, the literal entity
value is the exact text contained in the entity.] [Definition: For an internal entity,
the replacement text is the content of the entity, after replacement of character
references and parameter-entity references.] [Definition: For an external entity, the
replacement text is the content of the entity, after stripping the text declaration
(leaving any surrounding whitespace) if there is one but without any replacement of
character references or parameter-entity references.]
The literal entity value as given in an internal entity declaration ([755]EntityValue)
may contain character, parameter-entity, and general-entity references. Such references
MUST be contained entirely within the literal entity value. The actual replacement text
that is [756]included (or [757]included in literal) as described above MUST contain the
replacement text of any parameter entities referred to, and MUST contain the character
referred to, in place of any character references in the literal entity value; however,
general-entity references MUST be left as-is, unexpanded. For example, given the
following declarations:
then the replacement text for the entity " book " is:
La Peste: Albert Camus,
© 1947 Éditions Gallimard. &rights;
The general-entity reference " &rights; " would be expanded should the reference
" &book; " appear in the document's content or an attribute value.
These simple rules may have complex interactions; for a detailed discussion of a
difficult example, see [758]D Expansion of Entity and Character References.
4.6 Predefined Entities
[Definition: Entity and character references may both be used to escape the left angle
bracket, ampersand, and other delimiters. A set of general entities (amp, lt, gt, apos,
quot) is specified for this purpose. Numeric character references may also be used;
they are expanded immediately when recognized and MUST be treated as character data, so
the numeric character references " < " and " & " may be used to escape < and &
when they occur in character data.]
All XML processors MUST recognize these entities whether they are declared or not.
[759]For interoperability, valid XML documents SHOULD declare these entities, like any
others, before using them. If the entities lt or amp are declared, they MUST be
declared as internal entities whose replacement text is a character reference to the
respective character (less-than sign or ampersand) being escaped; the double escaping
is REQUIRED for these entities so that references to them produce a well-formed result.
If the entities gt, apos, or quot are declared, they MUST be declared as internal
entities whose replacement text is the single character being escaped (or a character
reference to that character; the double escaping here is OPTIONAL but harmless). For
example:
4.7 Notation Declarations
[Definition: Notations identify by name the format of [760]unparsed entities, the
format of elements which bear a notation attribute, or the application to which a
[761]processing instruction is addressed.]
[Definition: Notation declarations provide a name for the notation, for use in entity
and attribute-list declarations and in attribute specifications, and an external
identifier for the notation which may allow an XML processor or its client application
to locate a helper application capable of processing data in the given notation.]
Notation Declarations
[82] NotationDecl ::= '' [768][VC: Unique Notation Name]
[83] PublicID ::= 'PUBLIC' [769]S [770]PubidLiteral
Validity constraint: Unique Notation Name
A given [771]Name MUST NOT be declared in more than one notation declaration.
XML processors MUST provide applications with the name and external identifier(s) of
any notation declared and referred to in an attribute value, attribute definition, or
entity declaration. They MAY additionally resolve the external identifier into the
[772]system identifier, file name, or other information needed to allow the application
to call a processor for data in the notation described. (It is not an error, however,
for XML documents to declare and refer to notations for which notation-specific
applications are not available on the system where the XML processor or application is
running.)
4.8 Document Entity
[Definition: The document entity serves as the root of the entity tree and a
starting-point for an [773]XML processor.] This specification does not specify how the
document entity is to be located by an XML processor; unlike other entities, the
document entity has no name and might well appear on a processor input stream without
any identification at all.
5 Conformance
5.1 Validating and Non-Validating Processors
Conforming [774]XML processors fall into two classes: validating and non-validating.
Validating and non-validating processors alike MUST report violations of this
specification's well-formedness constraints in the content of the [775]document entity
and any other [776]parsed entities that they read.
[Definition: Validating processors MUST, at user option, report violations of the
constraints expressed by the declarations in the [777]DTD, and failures to fulfill the
validity constraints given in this specification.] To accomplish this, validating XML
processors MUST read and process the entire DTD and all external parsed entities
referenced in the document.
Non-validating processors are REQUIRED to check only the [778]document entity,
including the entire internal DTD subset, for well-formedness. [Definition: While they
are not required to check the document for validity, they are REQUIRED to process all
the declarations they read in the internal DTD subset and in any parameter entity that
they read, up to the first reference to a parameter entity that they do not read; that
is to say, they MUST use the information in those declarations to [779]normalize
attribute values, [780]include the replacement text of internal entities, and supply
[781]default attribute values.] Except when standalone="yes", they MUST NOT
[782]process [783]entity declarations or [784]attribute-list declarations encountered
after a reference to a parameter entity that is not read, since the entity may have
contained overriding declarations; when standalone="yes", processors MUST process these
declarations.
Note that when processing invalid documents with a non-validating processor the
application may not be presented with consistent information. For example, several
requirements for uniqueness within the document may not be met, including more than one
element with the same id, duplicate declarations of elements or notations with the same
name, etc. In these cases the behavior of the parser with respect to reporting such
information to the application is undefined.
5.2 Using XML Processors
The behavior of a validating XML processor is highly predictable; it must read every
piece of a document and report all well-formedness and validity violations. Less is
required of a non-validating processor; it need not read any part of the document other
than the document entity. This has two effects that may be important to users of XML
processors:
* Certain well-formedness errors, specifically those that require reading
external entities, may fail to be detected by a non-validating processor.
Examples include the constraints entitled [785]Entity Declared, [786]Parsed
Entity, and [787]No Recursion, as well as some of the cases described as
[788]forbidden in [789]4.4 XML Processor Treatment of Entities and
References.
* The information passed from the processor to the application may vary,
depending on whether the processor reads parameter and external entities. For
example, a non-validating processor may fail to [790]normalize attribute
values, [791]include the replacement text of internal entities, or supply
[792]default attribute values, where doing so depends on having read
declarations in external or parameter entities, or in the internal subset
after an unread parameter entity reference.
For maximum reliability in interoperating between different XML processors,
applications which use non-validating processors SHOULD NOT rely on any behaviors
not required of such processors. Applications which require DTD facilities not
related to validation (such as the declaration of default attributes and internal
entities that are or may be specified in external entities) SHOULD use validating
XML processors.
6 Notation
The formal grammar of XML is given in this specification using a simple Extended
Backus-Naur Form (EBNF) notation. Each rule in the grammar defines one symbol, in the
form
symbol ::= expression
Symbols are written with an initial capital letter if they are the start symbol
of a regular language, otherwise with an initial lowercase letter. Literal
strings are quoted.
Within the expression on the right-hand side of a rule, the following expressions
are used to match strings of one or more characters:
#xN
where N is a hexadecimal integer, the expression matches the character
whose number (code point) in ISO/IEC 10646 is N. The number of leading
zeros in the #xN form is insignificant.
[a-zA-Z], [#xN-#xN]
matches any [793]Char with a value in the range(s) indicated (inclusive).
[abc], [#xN#xN#xN]
matches any [794]Char with a value among the characters enumerated.
Enumerations and ranges can be mixed in one set of brackets.
[^a-z], [^#xN-#xN]
matches any [795]Char with a value outside the range indicated.
[^abc], [^#xN#xN#xN]
matches any [796]Char with a value not among the characters given.
Enumerations and ranges of forbidden values can be mixed in one set of
brackets.
"string"
matches a literal string [797]matching that given inside the double
quotes.
'string'
matches a literal string [798]matching that given inside the single
quotes.
These symbols may be combined to match more complex patterns as follows, where A
and B represent simple expressions:
(expression)
expression is treated as a unit and may be combined as described in this
list.
A?
matches A or nothing; optional A.
A B
matches A followed by B. This operator has higher precedence than
alternation; thus A B | C D is identical to (A B) | (C D).
A | B
matches A or B.
A - B
matches any string that matches A but does not match B.
A+
matches one or more occurrences of A. Concatenation has higher precedence
than alternation; thus A+ | B+ is identical to (A+) | (B+).
A*
matches zero or more occurrences of A. Concatenation has higher precedence
than alternation; thus A* | B* is identical to (A*) | (B*).
Other notations used in the productions are:
/* ... */
comment.
[ wfc: ... ]
well-formedness constraint; this identifies by name a constraint on
[799]well-formed documents associated with a production.
[ vc: ... ]
validity constraint; this identifies by name a constraint on [800]valid
documents associated with a production.
A References
A.1 Normative References
IANA-CHARSETS
(Internet Assigned Numbers Authority) [801]Official Names for Character
Sets, ed. Keld Simonsen et al. (See
http://www.iana.org/assignments/character-sets.)
IETF RFC 2119
IETF (Internet Engineering Task Force). [802]RFC 2119: Key words for use
in RFCs to Indicate Requirement Levels. Scott Bradner, 1997. (See
http://www.ietf.org/rfc/rfc2119.txt.)
IETF BCP 47
IETF (Internet Engineering Task Force). BCP 47, consisting of [803]RFC
4646: Tags for Identifying Languages, and [804]RFC 4647: Matching of
Language Tags, A. Phillips, M. Davis. 2006.
IETF RFC 3986
IETF (Internet Engineering Task Force). [805]RFC 3986: Uniform Resource
Identifier (URI): Generic Syntax. T. Berners-Lee, R. Fielding, L.
Masinter. 2005. (See http://www.ietf.org/rfc/rfc3986.txt.)
ISO/IEC 10646
ISO (International Organization for Standardization). ISO/IEC
10646-1:2000. Information technology -- Universal Multiple-Octet Coded
Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane
and ISO/IEC 10646-2:2001. Information technology -- Universal
Multiple-Octet Coded Character Set (UCS) -- Part 2: Supplementary Planes,
as, from time to time, amended, replaced by a new edition or expanded by
the addition of new parts. [Geneva]: International Organization for
Standardization. (See [806]http://www.iso.org/iso/home.htm for the latest
version.)
ISO/IEC 10646:2000
ISO (International Organization for Standardization). ISO/IEC
10646-1:2000. Information technology -- Universal Multiple-Octet Coded
Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
[Geneva]: International Organization for Standardization, 2000.
Unicode
The Unicode Consortium. The Unicode Standard, Version 5.0.0, defined by:
The Unicode Standard, Version 5.0 (Boston, MA, Addison-Wesley, 2007. ISBN
0-321-48091-0).
UnicodeNormal
The Unicode Consortium. [807]Unicode normalization forms. Mark Davis and
Martin Durst. 2008. (See http://unicode.org/reports/tr15/.)
A.2 Other References
Aho/Ullman
Aho, Alfred V., Ravi Sethi, and Jeffrey D. Ullman. Compilers: Principles,
Techniques, and Tools. Reading: Addison-Wesley, 1986, rpt. corr. 1988.
Brüggemann-Klein
Brüggemann-Klein, Anne. [808]Formal Models in Document Processing.
Habilitationsschrift. Faculty of Mathematics at the University of
Freiburg, 1993. (See
ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps.)
Brüggemann-Klein and Wood
Brüggemann-Klein, Anne, and Derick Wood. Deterministic Regular Languages.
Universität Freiburg, Institut für Informatik, Bericht 38, Oktober 1991.
Extended abstract in A. Finkel, M. Jantzen, Hrsg., STACS 1992, S. 173-184.
Springer-Verlag, Berlin 1992. Lecture Notes in Computer Science 577. Full
version titled One-Unambiguous Regular Languages in Information and
Computation 140 (2): 229-253, February 1998.
Clark
James Clark. [809]Comparison of SGML and XML. (See
http://www.w3.org/TR/NOTE-sgml-xml-971215.)
IANA-LANGCODES
(Internet Assigned Numbers Authority) [810]Registry of Language Tags (See
http://www.iana.org/assignments/language-subtag-registry.)
IETF RFC 2141
IETF (Internet Engineering Task Force). [811]RFC 2141: URN Syntax, ed. R.
Moats. 1997. (See http://www.ietf.org/rfc/rfc2141.txt.)
IETF RFC 3023
IETF (Internet Engineering Task Force). [812]RFC 3023: XML Media Types.
eds. M. Murata, S. St.Laurent, D. Kohn. 2001. (See
http://www.ietf.org/rfc/rfc3023.txt.)
IETF RFC 2781
IETF (Internet Engineering Task Force). [813]RFC 2781: UTF-16, an encoding
of ISO 10646, ed. P. Hoffman, F. Yergeau. 2000. (See
http://www.ietf.org/rfc/rfc2781.txt.)
ISO 639
(International Organization for Standardization). ISO 639:1988 (E). Code
for the representation of names of languages. [Geneva]: International
Organization for Standardization, 1988.
ISO 3166
(International Organization for Standardization). ISO 3166-1:1997 (E).
Codes for the representation of names of countries and their subdivisions
-- Part 1: Country codes [Geneva]: International Organization for
Standardization, 1997.
ISO 8879
ISO (International Organization for Standardization). ISO 8879:1986(E).
Information processing -- Text and Office Systems -- Standard Generalized
Markup Language (SGML). First edition -- 1986-10-15. [Geneva]:
International Organization for Standardization, 1986.
ISO/IEC 10744
ISO (International Organization for Standardization). ISO/IEC 10744-1992
(E). Information technology -- Hypermedia/Time-based Structuring Language
(HyTime). [Geneva]: International Organization for Standardization, 1992.
Extended Facilities Annexe. [Geneva]: International Organization for
Standardization, 1996.
WEBSGML
ISO (International Organization for Standardization). [814]ISO 8879:1986
TC2. Information technology -- Document Description and Processing
Languages. [Geneva]: International Organization for Standardization, 1998.
(See http://www.sgmlsource.com/8879/n0029.htm.)
XML Names
Tim Bray, Dave Hollander, and Andrew Layman, editors. [815]Namespaces in
XML. Textuality, Hewlett-Packard, and Microsoft. World Wide Web
Consortium, 1999. (See http://www.w3.org/TR/xml-names/.)
B Character Classes
Because of changes to productions [816][4] and [817][5], the productions in this
Appendix are now orphaned and not used anymore in determining name characters. This
Appendix may be removed in a future edition of this specification; other specifications
that wish to refer to the productions herein should do so by means of a reference to
the relevant production(s) in the [818]Fourth Edition of this specification.
Following the characteristics defined in the Unicode standard, characters are classed
as base characters (among others, these contain the alphabetic characters of the Latin
alphabet), ideographic characters, and combining characters (among others, this class
contains most diacritics). Digits and extenders are also distinguished.
Characters
[84] Letter ::= [819]BaseChar | [820]Ideographic
[85] BaseChar ::= [#x0041-#x005A] | [#x0061-#x007A] | [#x00C0-#x00D6]
| [#x00D8-#x00F6] | [#x00F8-#x00FF] | [#x0100-#x0131] | [#x0134-#x013E]
| [#x0141-#x0148] | [#x014A-#x017E] | [#x0180-#x01C3] | [#x01CD-#x01F0]
| [#x01F4-#x01F5] | [#x01FA-#x0217] | [#x0250-#x02A8] | [#x02BB-#x02C1] | #x0386
| [#x0388-#x038A] | #x038C | [#x038E-#x03A1] | [#x03A3-#x03CE] | [#x03D0-#x03D6]
| #x03DA | #x03DC | #x03DE | #x03E0 | [#x03E2-#x03F3] | [#x0401-#x040C]
| [#x040E-#x044F] | [#x0451-#x045C] | [#x045E-#x0481] | [#x0490-#x04C4]
| [#x04C7-#x04C8] | [#x04CB-#x04CC] | [#x04D0-#x04EB] | [#x04EE-#x04F5]
| [#x04F8-#x04F9] | [#x0531-#x0556] | #x0559 | [#x0561-#x0586] | [#x05D0-#x05EA]
| [#x05F0-#x05F2] | [#x0621-#x063A] | [#x0641-#x064A] | [#x0671-#x06B7]
| [#x06BA-#x06BE] | [#x06C0-#x06CE] | [#x06D0-#x06D3] | #x06D5 | [#x06E5-#x06E6]
| [#x0905-#x0939] | #x093D | [#x0958-#x0961] | [#x0985-#x098C] | [#x098F-#x0990]
| [#x0993-#x09A8] | [#x09AA-#x09B0] | #x09B2 | [#x09B6-#x09B9] | [#x09DC-#x09DD]
| [#x09DF-#x09E1] | [#x09F0-#x09F1] | [#x0A05-#x0A0A] | [#x0A0F-#x0A10]
| [#x0A13-#x0A28] | [#x0A2A-#x0A30] | [#x0A32-#x0A33] | [#x0A35-#x0A36]
| [#x0A38-#x0A39] | [#x0A59-#x0A5C] | #x0A5E | [#x0A72-#x0A74] | [#x0A85-#x0A8B]
| #x0A8D | [#x0A8F-#x0A91] | [#x0A93-#x0AA8] | [#x0AAA-#x0AB0] | [#x0AB2-#x0AB3]
| [#x0AB5-#x0AB9] | #x0ABD | #x0AE0 | [#x0B05-#x0B0C] | [#x0B0F-#x0B10]
| [#x0B13-#x0B28] | [#x0B2A-#x0B30] | [#x0B32-#x0B33] | [#x0B36-#x0B39] | #x0B3D
| [#x0B5C-#x0B5D] | [#x0B5F-#x0B61] | [#x0B85-#x0B8A] | [#x0B8E-#x0B90]
| [#x0B92-#x0B95] | [#x0B99-#x0B9A] | #x0B9C | [#x0B9E-#x0B9F] | [#x0BA3-#x0BA4]
| [#x0BA8-#x0BAA] | [#x0BAE-#x0BB5] | [#x0BB7-#x0BB9] | [#x0C05-#x0C0C]
| [#x0C0E-#x0C10] | [#x0C12-#x0C28] | [#x0C2A-#x0C33] | [#x0C35-#x0C39]
| [#x0C60-#x0C61] | [#x0C85-#x0C8C] | [#x0C8E-#x0C90] | [#x0C92-#x0CA8]
| [#x0CAA-#x0CB3] | [#x0CB5-#x0CB9] | #x0CDE | [#x0CE0-#x0CE1] | [#x0D05-#x0D0C]
| [#x0D0E-#x0D10] | [#x0D12-#x0D28] | [#x0D2A-#x0D39] | [#x0D60-#x0D61]
| [#x0E01-#x0E2E] | #x0E30 | [#x0E32-#x0E33] | [#x0E40-#x0E45] | [#x0E81-#x0E82]
| #x0E84 | [#x0E87-#x0E88] | #x0E8A | #x0E8D | [#x0E94-#x0E97] | [#x0E99-#x0E9F]
| [#x0EA1-#x0EA3] | #x0EA5 | #x0EA7 | [#x0EAA-#x0EAB] | [#x0EAD-#x0EAE] | #x0EB0
| [#x0EB2-#x0EB3] | #x0EBD | [#x0EC0-#x0EC4] | [#x0F40-#x0F47] | [#x0F49-#x0F69]
| [#x10A0-#x10C5] | [#x10D0-#x10F6] | #x1100 | [#x1102-#x1103] | [#x1105-#x1107]
| #x1109 | [#x110B-#x110C] | [#x110E-#x1112] | #x113C | #x113E | #x1140 | #x114C
| #x114E | #x1150 | [#x1154-#x1155] | #x1159 | [#x115F-#x1161] | #x1163 | #x1165
| #x1167 | #x1169 | [#x116D-#x116E] | [#x1172-#x1173] | #x1175 | #x119E | #x11A8
| #x11AB | [#x11AE-#x11AF] | [#x11B7-#x11B8] | #x11BA | [#x11BC-#x11C2] | #x11EB
| #x11F0 | #x11F9 | [#x1E00-#x1E9B] | [#x1EA0-#x1EF9] | [#x1F00-#x1F15]
| [#x1F18-#x1F1D] | [#x1F20-#x1F45] | [#x1F48-#x1F4D] | [#x1F50-#x1F57] | #x1F59
| #x1F5B | #x1F5D | [#x1F5F-#x1F7D] | [#x1F80-#x1FB4] | [#x1FB6-#x1FBC] | #x1FBE
| [#x1FC2-#x1FC4] | [#x1FC6-#x1FCC] | [#x1FD0-#x1FD3] | [#x1FD6-#x1FDB]
| [#x1FE0-#x1FEC] | [#x1FF2-#x1FF4] | [#x1FF6-#x1FFC] | #x2126 | [#x212A-#x212B]
| #x212E | [#x2180-#x2182] | [#x3041-#x3094] | [#x30A1-#x30FA] | [#x3105-#x312C]
| [#xAC00-#xD7A3]
[86] Ideographic ::= [#x4E00-#x9FA5] | #x3007 | [#x3021-#x3029]
[87] CombiningChar ::= [#x0300-#x0345] | [#x0360-#x0361]
| [#x0483-#x0486] | [#x0591-#x05A1] | [#x05A3-#x05B9] | [#x05BB-#x05BD] | #x05BF
| [#x05C1-#x05C2] | #x05C4 | [#x064B-#x0652] | #x0670 | [#x06D6-#x06DC]
| [#x06DD-#x06DF] | [#x06E0-#x06E4] | [#x06E7-#x06E8] | [#x06EA-#x06ED]
| [#x0901-#x0903] | #x093C | [#x093E-#x094C] | #x094D | [#x0951-#x0954]
| [#x0962-#x0963] | [#x0981-#x0983] | #x09BC | #x09BE | #x09BF | [#x09C0-#x09C4]
| [#x09C7-#x09C8] | [#x09CB-#x09CD] | #x09D7 | [#x09E2-#x09E3] | #x0A02 | #x0A3C
| #x0A3E | #x0A3F | [#x0A40-#x0A42] | [#x0A47-#x0A48] | [#x0A4B-#x0A4D]
| [#x0A70-#x0A71] | [#x0A81-#x0A83] | #x0ABC | [#x0ABE-#x0AC5] | [#x0AC7-#x0AC9]
| [#x0ACB-#x0ACD] | [#x0B01-#x0B03] | #x0B3C | [#x0B3E-#x0B43] | [#x0B47-#x0B48]
| [#x0B4B-#x0B4D] | [#x0B56-#x0B57] | [#x0B82-#x0B83] | [#x0BBE-#x0BC2]
| [#x0BC6-#x0BC8] | [#x0BCA-#x0BCD] | #x0BD7 | [#x0C01-#x0C03] | [#x0C3E-#x0C44]
| [#x0C46-#x0C48] | [#x0C4A-#x0C4D] | [#x0C55-#x0C56] | [#x0C82-#x0C83]
| [#x0CBE-#x0CC4] | [#x0CC6-#x0CC8] | [#x0CCA-#x0CCD] | [#x0CD5-#x0CD6]
| [#x0D02-#x0D03] | [#x0D3E-#x0D43] | [#x0D46-#x0D48] | [#x0D4A-#x0D4D] | #x0D57
| #x0E31 | [#x0E34-#x0E3A] | [#x0E47-#x0E4E] | #x0EB1 | [#x0EB4-#x0EB9]
| [#x0EBB-#x0EBC] | [#x0EC8-#x0ECD] | [#x0F18-#x0F19] | #x0F35 | #x0F37 | #x0F39
| #x0F3E | #x0F3F | [#x0F71-#x0F84] | [#x0F86-#x0F8B] | [#x0F90-#x0F95] | #x0F97
| [#x0F99-#x0FAD] | [#x0FB1-#x0FB7] | #x0FB9 | [#x20D0-#x20DC] | #x20E1
| [#x302A-#x302F] | #x3099 | #x309A
[88] Digit ::= [#x0030-#x0039] | [#x0660-#x0669] | [#x06F0-#x06F9]
| [#x0966-#x096F] | [#x09E6-#x09EF] | [#x0A66-#x0A6F] | [#x0AE6-#x0AEF]
| [#x0B66-#x0B6F] | [#x0BE7-#x0BEF] | [#x0C66-#x0C6F] | [#x0CE6-#x0CEF]
| [#x0D66-#x0D6F] | [#x0E50-#x0E59] | [#x0ED0-#x0ED9] | [#x0F20-#x0F29]
[89] Extender ::= #x00B7 | #x02D0 | #x02D1 | #x0387 | #x0640 | #x0E46
| #x0EC6 | #x3005 | [#x3031-#x3035] | [#x309D-#x309E] | [#x30FC-#x30FE]
The character classes defined here can be derived from the Unicode 2.0 character
database as follows:
* Name start characters must have one of the categories Ll, Lu, Lo, Lt, Nl.
* Name characters other than Name-start characters must have one of the
categories Mc, Me, Mn, Lm, or Nd.
* Characters in the compatibility area (i.e. with character code greater than
#xF900 and less than #xFFFE) are not allowed in XML names.
* Characters which have a font or compatibility decomposition (i.e. those with
a "compatibility formatting tag" in field 5 of the database -- marked by
field 5 beginning with a "An ampersand (&#38;) may be escaped
numerically (&#38;#38;) or with a general entity
(&amp;)". >
then the XML processor will recognize the character references when it parses the
entity declaration, and resolve them before storing the following string as the
value of the entity " example ":
An ampersand (&) may be escaped
numerically (&#38;) or with a general entity
(&amp;).
A reference in the document to " &example; " will cause the text to be reparsed,
at which time the start- and end-tags of the p element will be recognized and the
three references will be recognized and expanded, resulting in a p element with
the following content (all data, no delimiters or markup):
An ampersand (&) may be escaped
numerically (&) or with a general entity
(&).
A more complex example will illustrate the rules and their effects fully. In the
following example, the line numbers are solely for reference.
1
2
5
6 %xx;
7 ]>
8 This sample shows a &tricky; method.
This produces the following:
* in line 4, the reference to character 37 is expanded immediately, and the
parameter entity " xx " is stored in the symbol table with the value " %zz;
". Since the replacement text is not rescanned, the reference to parameter
entity " zz " is not recognized. (And it would be an error if it were, since
" zz " is not yet declared.)
* in line 5, the character reference " < " is expanded immediately and the
parameter entity " zz " is stored with the replacement text " ", which is a well-formed entity declaration.
* in line 6, the reference to " xx " is recognized, and the replacement text of
" xx " (namely " %zz; ") is parsed. The reference to " zz " is recognized in
its turn, and its replacement text (" ") is
parsed. The general entity " tricky " has now been declared, with the
replacement text " error-prone ".
* in line 8, the reference to the general entity " tricky " is recognized, and
it is expanded, so the full content of the test element is the
self-describing (and ungrammatical) string This sample shows a error-prone
method.
In the following example
the replacement text of x is the four characters "<" because references to
general entities in entity values are [823]bypassed. The replacement text of lt
is a character reference to the less-than character, for example the five
characters "<" (see [824]4.6 Predefined Entities). Since neither of these
contains a less-than character the result is well-formed.
If the definition of x had been
then the document would not have been well-formed, because the replacement text
of x would be the single character "
Usage: http://www.kk-software.de/kklynxview/get/URL
e.g. http://www.kk-software.de/kklynxview/get/http://www.kk-software.de
Errormessages are in German, sorry ;-)