This document is also available in these non-normative formats: XML and Recent revisions.
Copyright © 2005 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
This document defines serialization of an instance of the data model as defined in [XQuery 1.0 and XPath 2.0 Data Model] into a sequence of octets. Serialization is designed to be a component that can be used by other specifications such as [XSL Transformations (XSLT) Version 2.0] or [XQuery 1.0: An XML Query Language].
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 W3C technical reports index at http://www.w3.org/TR/.
This is a Candidate Recommendation as described in the Process Document. This document is intended for review by W3C members and other interested parties. The publication of this document constitutes a call for implementations of this specification. This specification will remain a Candidate Recommendation until at least 28 February 2006.
This document has been jointly produced by the XML Query Working Group (WG) and the XSL Working Group, both of which are part of the XML Activity. Publication as a Candidate Recommendation does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This draft includes corrections and changes based on public comments recorded in the W3C public Bugzilla repository (http://www.w3.org/Bugs/Public/) used for Last Call issues tracking. A list of substantive changes since the Last Call Working Draft of 04 April 2005 can be found in E Revision Log.
Comments on this document should be made in W3C's public Bugzilla system (instructions can be found at http://www.w3.org/XML/2005/04/qt-bugzilla). If access to that system is not feasible, you may send your comments to the W3C XSLT/XPath/XQuery mailing list, public-qt-comments@w3.org. It will be very helpful if you include the string [Ser] in the subject line of your comment, whether made in Bugzilla or in email. Each Bugzilla entry and email message should contain only one comment. Archives of the comments and responses are available at http://lists.w3.org/Archives/Public/public-qt-comments/.
The XML Query and XSL Working Groups plan to submit this specification for consideration as a W3C Proposed Recommendation as soon as both [XQuery 1.0: An XML Query Language] and [XSL Transformations (XSLT) Version 2.0] have been submitted for consideration as W3C Proposed Recommendations.
The XML Query and XPath Test Suite is under development. Implementors are encouraged to run this test suite and report their results.
The patent policy for this document is the 5 February 2004 W3C Patent Policy. Patent disclosures relevant to this specification may be found on the XML Query Working Group's patent disclosure page and the XSL Working Group's patent disclosure page. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) with respect to this specification should disclose the information in accordance with section 6 of the W3C Patent Policy.
1 Introduction
1.1 Terminology
2 Sequence Normalization
3 Serialization Parameters
4 Phases of Serialization
5 XML Output Method
5.1 The Influence of Serialization Parameters upon the XML Output Method
5.1.1 XML Output Method: the version Parameter
5.1.2 XML Output Method: the encoding Parameter
5.1.3 XML Output Method: the indent Parameter
5.1.4 XML Output Method: the cdata-section-elements Parameter
5.1.5 XML Output Method: the omit-xml-declaration and standalone Parameters
5.1.6 XML Output Method: the doctype-system and doctype-public Parameters
5.1.7 XML Output Method: the undeclare-prefixes Parameter
5.1.8 XML Output Method: the normalization-form Parameter
5.1.9 XML Output Method: the media-type Parameter
5.1.10 XML Output Method: the use-character-maps Parameter
5.1.11 XML Output Method: the byte-order-mark Parameter
5.1.12 XML Output Method: the escape-uri-attributes Parameter
5.1.13 XML Output Method: the include-content-type Parameter
6 XHTML Output Method
6.1 The Influence of Serialization Parameters upon the XHTML Output Method
6.1.1 XHTML Output Method: the version Parameter
6.1.2 XHTML Output Method: the encoding Parameter
6.1.3 XHTML Output Method: the indent Parameter
6.1.4 XHTML Output Method: the cdata-section-elements Parameter
6.1.5 XHTML Output Method: the omit-xml-declaration and standalone Parameters
6.1.6 XHTML Output Method: the doctype-system and doctype-public Parameters
6.1.7 XHTML Output Method: the undeclare-prefixes Parameter
6.1.8 XHTML Output Method: the normalization-form Parameter
6.1.9 XHTML Output Method: the media-type Parameter
6.1.10 XHTML Output Method: the use-character-maps Parameter
6.1.11 XHTML Output Method: the byte-order-mark Parameter
6.1.12 XHTML Output Method: the escape-uri-attributes Parameter
6.1.13 XHTML Output Method: the include-content-type Parameter
7 HTML Output Method
7.1 Markup for Elements
7.2 Writing Attributes
7.3 Writing Character Data
7.4 The Influence of Serialization Parameters upon the HTML Output Method
7.4.1 HTML Output Method: the version Parameter
7.4.2 HTML Output Method: the encoding Parameter
7.4.3 HTML Output Method: the indent Parameter
7.4.4 HTML Output Method: the cdata-section-elements Parameter
7.4.5 HTML Output Method: the omit-xml-declaration and standalone Parameters
7.4.6 HTML Output Method: the doctype-system and doctype-public Parameters
7.4.7 HTML Output Method: the undeclare-prefixes Parameter
7.4.8 HTML Output Method: the normalization-form Parameter
7.4.9 HTML Output Method: the media-type Parameter
7.4.10 HTML Output Method: the use-character-maps Parameter
7.4.11 HTML Output Method: the byte-order-mark Parameter
7.4.12 HTML Output Method: the escape-uri-attributes Parameter
7.4.13 HTML Output Method: the include-content-type Parameter
8 Text Output Method
8.1 The Influence of Serialization Parameters upon the Text Output Method
8.1.1 Text Output Method: the version Parameter
8.1.2 Text Output Method: the encoding Parameter
8.1.3 Text Output Method: the indent Parameter
8.1.4 Text Output Method: the cdata-section-elements Parameter
8.1.5 Text Output Method: the omit-xml-declaration and standalone Parameters
8.1.6 Text Output Method: the doctype-system and doctype-public Parameters
8.1.7 Text Output Method: the undeclare-prefixes Parameter
8.1.8 Text Output Method: the normalization-form Parameter
8.1.9 Text Output Method: the media-type Parameter
8.1.10 Text Output Method: the use-character-maps Parameter
8.1.11 Text Output Method: the byte-order-mark Parameter
8.1.12 Text Output Method: the escape-uri-attributes Parameter
8.1.13 Text Output Method: the include-content-type Parameter
9 Character Maps
10 Conformance
A References
A.1 Normative References
A.2 Informative References
B Summary of Error Conditions
C List of URI Attributes
D Checklist of Implementation-Defined Features (Non-Normative)
E Revision Log (Non-Normative)
This document defines serialization of the W3C XQuery 1.0 and XPath 2.0 Data Model (XDM), which is the data model of at least [XML Path Language (XPath) 2.0], [XSL Transformations (XSLT) Version 2.0], and [XQuery 1.0: An XML Query Language], and any other specifications that reference it.
Serialization is the process of converting an instance of the [XQuery 1.0 and XPath 2.0 Data Model] into a sequence of octets. Serialization is well-defined for most data model instances.
In this specification, where they appear in upper case, the words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", "MAY", "REQUIRED", and "RECOMMENDED" are to be interpreted as described in [RFC2119].
[Definition: As is indicated in 10 Conformance, conformance criteria for serialization are determined by other specifications that refer to this specification. A serializer is software that implements some or all of the requirements of this specification in accordance with such conformance criteria.] A serializer is not REQUIRED to directly provide a programming interface that permits a user to set serialization parameters or to provide an input sequence for serialization.
Certain aspects of serialization are described in this specification as implementation-defined or implementation-dependent.
[Definition: Implementation-defined indicates an aspect that MAY differ between serializers, but whose actual behaviour MUST be specified either by another specification that sets conformance criteria for serialization (see 10 Conformance) or in documentation that accompanies the serializer.]
[Definition: Implementation-dependent indicates an aspect that MAY differ between serializers, and whose actual behaviour is not REQUIRED to be specified either by another specification that sets conformance criteria for serialization (see 10 Conformance) or in documentation that accompanies the serializer.]
[Definition: In some instances, the sequence that is input to serialization cannot be successfully converted into a sequence of octets given the set of serialization parameter (3 Serialization Parameters) values specified. A serialization error is said to occur in such an instance.] In some cases, a serializer is REQUIRED to signal such an error. What it means to signal a serialization error is determined by the relevant conformance criteria (10 Conformance) to which the serializer conforms. In other cases, there is an implementation-defined choice between signaling a serialization error and performing a recovery action. Such a recovery action will allow a serializer to produce a sequence of octets that might not fully reflect the usual requirements of the parameter settings that are in effect.
Many terms used in this document are defined in the XPath specification [XML Path Language (XPath) 2.0] or the Data Model specification [XQuery 1.0 and XPath 2.0 Data Model]. Particular attention is drawn to the following:
[Definition: The term atomization is defined in Section 2.4.2 AtomizationXP. It is a process that takes as input a sequence of nodes and atomic valuesXP, and returns a sequence of atomic valuesXP, in which the nodes are replaced by their typed valuesXP as defined in [XQuery 1.0 and XPath 2.0 Data Model].]
[Definition: The term Node is defined as part of Section 6 NodesDM. There are seven kinds of nodes in the data model: document, element, attribute, text, namespace, processing instruction, and comment.]
[Definition: The term sequence is defined in Section 2 BasicsXP. A sequence is an ordered collection of zero or more items.]
[Definition: The term string value is defined in Section 5.13 string-value AccessorDM. Every node has a string value. For example, the string value of an element is the concatenation of the string values of all its descendant text nodes.]
[Definition: The term expanded QName is defined in Section 2 BasicsXP. An expanded QName consists of an optional namespace URI and a local name. An expanded QName also retains its original namespace prefix (if any), to facilitate casting the expanded QName into a string.]
[Definition: An element or attribute that is in no namespace, or an expanded-QName whose namespace part is an empty sequence, is referred to as having a null namespace URI].
[Definition: An element or attribute that does not have a null namespace URI, is referred to as having a non-null namespace URI].
An instance of the data model that is input to the serialization process is a sequence. Prior to serializing a sequence using any of the output methods whose behavior is specified by this document (3 Serialization Parameters), the serializer MUST first compute a normalized sequence for serialization; it is the normalized sequence that is actually serialized. [Definition: The purpose of sequence normalization is to create a sequence that can be serialized as a well-formed XML document or external general parsed entity, that also reflects the content of the input sequence to the extent possible.] [Definition: The result of the sequence normalization process is a result tree.]
The normalized sequence for serialization is constructed by applying all of the following rules in order, with the initial sequence being input to the first step, and the sequence that results from any step being used as input to the subsequent step. For any implementation-defined output method, it is implementation-defined whether this sequence normalization process takes place.
Where the process of converting the input sequence to a normalized sequence indicates that a value MUST be cast to xs:string
, that operation is defined in Section 17.1.2 Casting to xs:string and xdt:untypedAtomicFO of [XQuery 1.0 and XPath 2.0 Functions and Operators]. The steps in computing the normalized sequence are:
If the sequence that is input to serialization is empty, create a sequence S1 that consists of a zero-length string. Otherwise, copy each item in the sequence that is input to serialization to create the new sequence S1.
For each item in S1, if the item is atomic, obtain the lexical representation of the item by casting it to an xs:string
and copy the string representation to the new sequence; otherwise, copy the item, which will be a node, to the new sequence. The new sequence is S2.
For each subsequence of adjacent strings in S2, copy a single string to the new sequence equal to the values of the strings in the subsequence concatenated in order, each separated by a single space. Copy all other items to the new sequence. The new sequence is S3.
For each item in S3, if the item is a string, create a text node in the new sequence whose string value is equal to the string; otherwise, copy the item to the new sequence. The new sequence is S4.
For each item in S4, if the item is a document node, copy its children to the new sequence; otherwise, copy the item to the new sequence. The new sequence is S5.
For each subsequence of adjacent text nodes in S5, copy a single text node to the new sequence equal to the values of the text nodes in the subsequence concatenated in order. Any text nodes with values of zero length are dropped. Copy all other items to the new sequence. The new sequence is S6.
It is a serialization error [err:SENR0001] if an item in S6 is an attribute node or a namespace node. Otherwise, construct a new sequence, S7, that consists of a single document node and copy all the items in the sequence, which are all nodes, as children of that document node.
S7 is the normalized sequence.
The result tree rooted at the document node that is created by the final step of this sequence normalization process is the instance of the data model to which the rules of the appropriate output method are applied. If the sequence normalization process results in a serialization error, the serializer MUST signal the error.
Note:
The sequence normalization process for a sequence $seq
is equivalent to constructing a document node using the XSLT instruction:
<xsl:document> <xsl:copy-of select="$seq"/> </xsl:document>
or the XQuery expression:
document { for $s in $seq return if ($s instance of document-node()) then $s/child::node() else $s }
This process results in a serialization error [err:SENR0001] if sequences contain parentless attribute and/or namespace nodes.
There are a number of parameters that influence how serialization is performed. Host languages MAY allow users to specify any or all of these parameters, but they are not REQUIRED to be able to do so. However, the host language specification MUST specify how the value of all applicable parameters is to be determined.
It is a serialization error [err:SEPM0016] if a parameter value is invalid for the given parameter. It is the responsibility of the host language to specify how invalid values should be handled at the level of that language.
The following serialization parameters are defined:
Serialization parameter name | Permitted values for parameter |
---|---|
byte-order-mark |
One of the enumerated values yes or no . This parameter indicates whether the serialized sequence of octets is to be preceded by a Byte Order Mark. (See Section 5.1 of [Unicode Encoding].) The actual octet order used is implementation-dependent. If the encoding defines no Byte Order Mark, or if the Byte Order Mark is prohibited for the specific Unicode encoding or implementation environment,
then this parameter is ignored. |
cdata-section-elements |
A list of expanded QNames, possibly empty. |
doctype-public |
A string of Unicode characters. This parameter may be absent. |
doctype-system |
A string of Unicode characters. This parameter may be absent. |
encoding |
A string of Unicode characters in the range #x21 to #x7E (that is, printable ASCII characters); the value SHOULD be a charset registered with the Internet Assigned Numbers Authority [IANA], [RFC2278] or begin with the characters x- or X- . |
escape-uri-attributes |
One of the enumerated values yes or no . |
include-content-type |
One of the enumerated values yes or no . |
indent |
One of the enumerated values yes or no . |
media-type |
A string of Unicode characters specifying the media type (MIME content type) [RFC2046]; the charset parameter of the media type MUST NOT be specified explicitly in the value of the media-type parameter. If the destination of the serialized output is annotated with a media type, this parameter MAY be used to provide such an annotation. For example, it MAY be used to set the media type in an HTTP header. |
method |
An expanded QName with a null namespace URI, and the local part of the name equal to one of xml , xhtml , html or text , or having a non-null namespace URI. If the namespace URI is non-null, the parameter specifies an implementation-defined output method. |
normalization-form |
One of the enumerated values NFC , NFD , NFKC , NFKD , fully-normalized , none or an implementation-defined value. |
omit-xml-declaration |
One of the enumerated values yes or no . |
standalone |
One of the enumerated values yes , no or omit . |
undeclare-prefixes |
One of the enumerated values yes or no . |
use-character-maps |
A list of pairs, possibly empty, with each pair consisting of a single Unicode character and a string of Unicode characters. |
version |
A string of Unicode characters. |
The value of the method
parameter is an expanded QName. If the value has a null namespace URI, then the local name identifies a method specified in this document and MUST be one of xml
, html
, xhtml
, or text
; in this case, the output method specified MUST be used for serializing. If the
namespace URI is non-null, then it identifies an implementation-defined output method; the behavior in this case is not specified by this document.
In those cases where they have no important effect on the content of the serialized result, details of the output methods defined by this specification are left unspecified and are regarded as implementation-dependent. Whether a serializer uses apostrophes or quotation marks to delimit attribute values in the XML output method is an example of such a detail.
The detailed semantics of each parameter will be described separately for each output method for which it is applicable. If the semantics of a parameter are not described for an output method, then it is not applicable to that output method.
Implementations MAY define additional serialization parameters, and MAY allow users to do so. For this purpose, the name of a serialization parameter is considered to be a QName; the parameters listed above are QNames in no namespace, while any additional serialization parameters must have names that are namespace-qualified. If the serialization method is one of the four methods xml
, html
, xhtml
, or text
, then the
additional serialization parameters MAY affect the output of the serializer to the extent (but only to the extent) that this specification leaves the output implementation-defined or implementation-dependent. For example, such parameters might control whether namespace declarations on an element are written before or after the attributes of the element, or they might define the
number of space or tab characters to be inserted when the indent
parameter is set to yes
; but they could not instruct the serializer to suppress the error that occurs when the HTML output method encounters illegal characters (see error [err:SERE0014]).
Following the sequence normalization process described in 2 Sequence Normalization, serialization can be regarded as involving three phases of processing.
For an implementation-defined output method, any of these phases MAY be skipped or MAY be performed in a different order than is specified here. For the output methods defined in this specification, these phases are carried out sequentially as follows:
Markup generation produces the character representation of those parts of the serialized result that describe the structure of the normalized sequence. In the cases of the XML, HTML and XHTML output methods, this phase produces the character representations of the following:
the document type declaration;
start tags and end tags (except for attribute values, whose representation is produced by the character expansion phase);
processing instructions; and
comments.
In the cases of the XML and XHTML output methods, this phase also produces the following:
the XML or text declaration; and
empty element tags (except for the attribute values);
Character expansion is concerned with the representation of characters appearing in text and attribute nodes in the normalized sequence. The substitution processes that apply are listed below, in priority order: a character that is handled by one process in this list will be unaffected by processes appearing later in the list, except that a character affected by Unicode Normalization MAY be affected by creation of CDATA sections and by character escaping:
URI escaping, as determined by the escape-uri-attributes
parameter that is applicable to HTML and XHTML output methods. [Definition: URI escaping is a process where the content of URI attribute values are first normalized to NFC using the method defined in Section 7.4.6 fn:normalize-unicodeFO of [XQuery 1.0 and XPath 2.0 Functions and Operators], then escaped using the method defined in Section 7.4.12 fn:escape-html-uriFO of [XQuery 1.0 and XPath 2.0 Functions and Operators].] [Definition: The values of attributes listed in C List of URI Attributes are URI attribute values. Namespace declaration attributes and attributes whose type annotation is xs:anyURI
are excluded from this list.]
Character mapping, as determined by the use-character-maps
parameter. Text nodes that are children of elements specified by the cdata-section-elements
parameter are not affected by this step.
Unicode Normalization, if requested by the normalization-form
parameter. [Definition: Unicode Normalization is the process of removing alternate representations of equivalent sequences from textual data, to convert the data into a form that can be binary-compared for equivalence, as specified in [UAX #15: Unicode Normalization Forms]. For specific recommendations for character normalization on the World Wide Web, see [Character Model for the World Wide Web 1.0: Normalization].]
The meanings associated with the possible values of the normalization-form
parameter are as follows:
NFC
specifies the serialized result will be in Normalization Form C, using the rules specified in [Character Model for the World Wide Web 1.0: Normalization].
NFD
specifies the serialized result will be in Normalization Form D, as specified in [UAX #15: Unicode Normalization Forms].
NFKC
specifies the serialized result will be in Normalization Form KC, as specified in [UAX #15: Unicode Normalization Forms].
NFKD
specifies the serialized result will be in Normalization Form KD, as specified in [UAX #15: Unicode Normalization Forms].
fully-normalized
specifies the serialized result will be in fully normalized text, as specified in [Character Model for the World Wide Web 1.0: Normalization].
none
specifies that no Unicode Normalization will be applied.
An implementation-defined value has an implementation-defined effect.
Creation of CDATA sections, as determined by the cdata-section-elements
parameter. Note that this is also affected by the encoding
parameter, in that characters not present in the selected encoding cannot be represented in a CDATA section.
Escaping according to XML or HTML rules of special characters that cannot be represented in the selected encoding, for example, replacing <
with <
.
Encoding, as controlled by the encoding
parameter, converts the character stream produced by the previous phases into an octet stream.
Note:
Serialization is only defined in terms of encoding the result as a stream of octets. However, a serializer may provide an option that allows the encoding phase to be skipped, so that the result of serialization is a stream of Unicode characters. The effect of any such option is implementation-defined, and a serializer is not required to support such an option.
The XML output method serializes the normalized sequence as an XML entity that MUST satisfy the rules for either a well-formed XML document entity or a well-formed XML external general parsed entity, or both. A serialization error [err:SERE0003] results if the serializer is unable to satisfy those rules, except for content modified by the character expansion phase of serialization, as described in 4 Phases of Serialization, which could result in the serialized output being not well-formed but will not result in a serialization error. If a serialization error results, the serializer MUST signal the error.
If the document node of the normalized sequence has a single element node child and no text node children, then the serialized output is a well-formed XML document entity, and the serialized output MUST conform to the appropriate version of the XML Namespaces Recommendation [XML Names] or [XML Names 1.1]. If the normalized sequence does not take this form, then the serialized output is a well-formed XML external general parsed entity, which, when referenced within a trivial XML document wrapper like this:
<?xml version="version"?> <!DOCTYPE doc [ <!ENTITY e SYSTEM "entity-URI"> ]> <doc>&e;</doc>
where entity-URI
is a URI for the entity, and the value of the version
pseudo-attribute is the value of the version
parameter, produces a document which MUST itself be a well-formed XML document conforming to the corresponding version of the XML Namespaces Recommendation [XML Names] or [XML Names 1.1].
[Definition: A reconstructed tree may be constructed by parsing the XML document and converting it into an instance of the data model as specified in [XQuery 1.0 and XPath 2.0 Data Model].] The result of serialization MUST be such that the reconstructed tree is the same as the result tree except for the following permitted differences:
If the document was produced by adding a document wrapper, as described above, then it will contain an extra doc
element as the document element.
The order of attribute and namespace nodes in the two trees MAY be different.
The following properties of corresponding nodes in the two trees MAY be different:
The reconstructed tree MAY contain additional attributes and text nodes resulting from the expansion of default and fixed values in its DTD or schema.
The type annotations of the nodes in the two trees MAY be different. Type annotations in a result tree are discarded when the tree is serialized. Any new type annotations obtained by parsing the document will depend on whether the serialized XML document is assessed against a schema, and this MAY result in type annotations that are different from those in the original result tree.
Note:
In order to influence the type annotations in the instance of the data model that would result from processing a serialized XML document, the author of the XSLT stylesheet, XQuery expression or other process might wish to create the instance of the data model that is input to the serialization process so that it makes use of mechanisms provided by [XML Schema], such as xsi:type
and xsi:schemaLocation
attributes. The serialization process will not
automatically create such attributes in the serialized document if those attributes were not part of the result tree that is to be serialized.
Similarly, it is possible that an element node in the instance of the data model that is to be serialized has the nilled
property with the value true
, but no xsi:nil
attribute. The serialization process will not create such an attribute in the serialized document simply to reflect the value of the property. The value of the nilled
property has no direct effect on the serialized result.
Additional namespace nodes MAY be present in the reconstructed tree if the serialization process did not undeclare one or more namespaces, as described in 5.1.7 XML Output Method: the undeclare-prefixes Parameter, and the starting instance of the data model contained an element node with a namespace node that declared some prefix, but a child element of that node did not have any namespace node that declared the same prefix.
The result tree MAY contain namespace nodes that are not present in the reconstructed tree, as the process of creating an instance of the data model MAY ignore namespace declarations in some circumstances. See Section 6.2.3 Construction from an InfosetDM and Section 6.2.4 Construction from a PSVIDM of [XQuery 1.0 and XPath 2.0 Data Model] for additional information.
If the indent
parameter has the value yes
,
additional text nodes consisting of whitespace characters MAY be present in the reconstructed tree; and
text nodes in the result tree that contained only whitespace characters MAY correspond to text nodes in the reconstructed tree that contain additional whitespace characters that were not present in the result tree
See 5.1.3 XML Output Method: the indent Parameter for more information on the indent
parameter.
Additional nodes MAY be present in the reconstructed tree due to the effect of character mapping in the character expansion phase, and the values of attribute nodes and text nodes in the reconstructed tree MAY be different from those in the result tree, due to the effects of URI expansion, character mapping and Unicode Normalization in the character expansion phase of serialization.
Note:
The use-character-maps
parameter can cause arbitrary characters to be inserted into the serialized XML document in an unescaped form, including characters that would be considered to be part of XML markup. Such characters could result in arbitrary new element nodes, attribute nodes, and so on, in the reconstructed tree that results from processing the
serialized XML document.
A consequence of this rule is that certain characters MUST be output as character references, to ensure that they survive the round trip through serialization and parsing. Specifically, CR, NEL and LINE SEPARATOR characters in text nodes MUST be output respectively as "
", "…
", and "

", or their equivalents; while CR, NL, TAB, NEL and LINE SEPARATOR characters in
attribute nodes MUST be output respectively as "
", "

", "	
", "…
", and "

", or their equivalents. In addition, the non-whitespace control characters #x1 through #x1F and #x7F through #x9F in text nodes and attribute nodes MUST be output as character
references.
For example, an attribute with the value "x" followed by "y" separated by a newline will result in the output "x
y"
(or with any equivalent character reference). The XML output cannot be "x" followed by a literal newline followed by a "y" because after parsing, the attribute value would be "x y"
as a consequence of the XML attribute normalization rules.
Note:
XML 1.0 did not permit an XML processor to normalize NEL or LINE SEPARATOR characters to a LINE FEED character. However, if a document entity that specifies version 1.1 invokes an external general parsed entity with no text declaration or a text declaration that specifies version 1.0, the external parsed entity is processed according to the rules of XML 1.1. For this reason, NEL and LINE SEPARATOR characters in text and attribute nodes must always be escaped using
character references, regardless of the value of the version
parameter.
XML 1.0 permitted control characters in the range #x7F through #x9F to appear as literal characters in an XML document, but XML 1.1 requires such characters, other than NEL, to be escaped as character references. An external general parsed entity with no text declaration or a text declaration that specifies a version pseudo-attribute with value 1.0
that is invoked by an XML 1.1 document entity MUST follow the rules of XML 1.1. Therefore, the non-whitespace control
characters in the ranges #x1 through #x1F and #x7F through #x9F, other than NEL, MUST always be escaped, regardless of the value of the version
parameter.
It is a serialization error [err:SEPM0004] to specify the doctype-system parameter, or to specify the standalone parameter with a value other than omit
, if the instance of the data model contains text nodes or multiple element nodes as children of the root node. The serializer MUST either signal the error, or recover by ignoring the request to output a document type declaration or standalone
parameter.
The result of serialization using the XML output method is not guaranteed to be well-formed XML if character maps have been specified (see 9 Character Maps).
version
ParameterThe version
parameter specifies the version of XML and the version of Namespaces in XML to be used for outputting the instance of the data model. The version output in the XML declaration (if an XML declaration is not omitted) MUST correspond to the version of XML that the serializer used for outputting the instance of the data model. The value of the version
parameter MUST match the VersionNum XML production of the XML Recommendation [XML10] or [XML11].
If the serialized result would contain an NCName Names that contains a character that is not permitted by the version of Namespaces in XML specified by the version
parameter, a serialization error [err:SERE0005] results. The serializer MUST
signal the error.
If the serialized result would contain a character that is not permitted by the version of XML specified by the version
parameter, a serialization error [err:SERE0006] results. The serializer MUST signal the error.
For example, if the version
parameter has the value 1.0
, and the instance of the data model contains a non-whitespace control character in the range #x1 to #x1F, a serialization error [err:SERE0006] results. If the version
parameter has the value 1.1
and a comment node in the instance of the data model contains a
non-whitespace control character in the range #x1 to #x1F or a control character other than NEL in the range #x7F to #x9F, a serialization error [err:SERE0006] results.
encoding
ParameterThe encoding
parameter specifies the encoding to be used for outputting the instance of the data model. Serializers are REQUIRED to support values of UTF-8
and UTF-16
. A serialization error [err:SESU0007] occurs if an output encoding other than UTF-8
or UTF-16
is requested and
the serializer does not support that encoding. The serializer MUST signal the error, or recover by using UTF-8
or UTF-16
instead. The serializer MUST NOT use an encoding whose name does not match the EncName XML production of the XML
Recommendation [XML10].
When outputting a newline character in the instance of the data model, the serializer is free to represent it using any character sequence that will be normalized to a newline character by an XML parser, unless a specific mapping for the newline character is provided in a character map (see 9 Character Maps).
When outputting any other character that is defined in the selected encoding, the character MUST be output using the correct representation of that character in the selected encoding.
It is possible that the instance of the data model will contain a character that cannot be represented in the encoding that the serializer is using for output. In this case, if the character occurs in a context where XML recognizes character references (that is, in the value of an attribute node or text node), then the character MUST be output as a character reference. A serialization error [err:SERE0008] occurs if such a character appears in a context where character references are not allowed (for example, if the character occurs in the name of an element). The serializer MUST signal the error.
For example, if a text node contains the character LATIN SMALL LETTER E WITH ACUTE (#xE9), and the value of the encoding
parameter is US-ASCII
, the character MUST be serialized as a character reference. If a comment node contains the same character, a serialization error [err:SERE0008]
results.
indent
ParameterIf the indent
parameter has the value yes
, then the XML output method MAY output whitespace in addition to the whitespace in the instance of the data model in order to indent the result so that a person will find it easier to read; if the indent
parameter has the value no
, it MUST NOT output any additional whitespace. If the XML output method does output additional whitespace, it MUST use an algorithm
to output additional whitespace that satisfies all of the following constraints:
Whitespace characters MUST NOT be added adjacent to a text node that contains non-whitespace characters.
Whitespace characters MUST NOT be added other than adjacent to an element node, that is, immediately before a start tag or immediately after an end tag.
Whitespace characters MUST NOT be inserted in a part of the result document that is controlled by an xml:space
attribute with value preserve
. (See [XML10] for more information about the xml:space
attribute.)
Whitespace characters SHOULD NOT be added in places where the characters would constitute significant whitespace, for example, in the content of an element whose content model is known to be mixed.
In any location where the above rules allow the addition of whitespace characters, existing whitespace characters MAY also be removed or replaced. For example, a tab MAY be inserted as a replacement for existing spaces.
Note:
The effect of these rules is to ensure that whitespace is only added in places where (a) XSLT's <xsl:strip-space>
declaration could cause it to be removed, and (b) it does not affect the string value of any element node with simple content. It is usually not safe to indent document types that include elements with mixed content.
Note:
The whitespace added may possibly be based on whitespace stripped from either the source document or the stylesheet (in the case of XSLT), or guided by other means that might depend on the host language, in the case of an instance of the data model created using some other process.
cdata-section-elements
ParameterThe cdata-section-elements
parameter contains a list of expanded QNames. If the expanded QName of the parent of a text node is a member of the list, then the text node MUST be output as a CDATA section, except in those circumstances described below.
If the text node contains the sequence of characters ]]>
, then the currently open CDATA section MUST be closed following the ]]
and a new CDATA section opened before the >
.
If the text node contains characters that are not representable in the character encoding being used to output the instance of the data model, then the currently open CDATA section MUST be closed before such characters, the characters MUST be output using character references or entity references, and a new CDATA section MUST be opened for any further characters in the text node.
CDATA sections MUST NOT be used except where they have been explicitly requested by the user, either by using the cdata-section-elements
parameter, or by using some other implementation-defined mechanism.
Note:
This is phrased to permit an implementor to provide an option that attempts to preserve CDATA sections present in the source document.
omit-xml-declaration
and standalone
ParametersThe XML output method MUST output an XML declaration if the omit-xml-declaration
parameter has the value no
. The XML declaration MUST include both version information and an encoding declaration. If the standalone
parameter has the value yes
or the value no
, the XML declaration MUST include a standalone document declaration with the same value as the value of the standalone
parameter. If the standalone
parameter has the value omit
, the XML declaration MUST NOT include a standalone document declaration; this ensures that it is both an XML declaration (allowed at the beginning of a document entity) and a text declaration (allowed at the beginning of an external general parsed entity).
A serialization error [err:SEPM0009] results if the omit-xml-declaration
parameter has the value yes
, and
the standalone
parameter has a value other than omit
; or
the version
parameter has a value other than 1.0
and the doctype-system
parameter is specified.
Otherwise, if the omit-xml-declaration
parameter has the value yes
, the XML output method MUST NOT output an XML declaration.
doctype-system
and doctype-public
ParametersIf the doctype-system
parameter is specified, the XML output method MUST output a document type declaration immediately before the first element. The name following <!DOCTYPE
MUST be the name of the first element, if any. If the doctype-public
parameter is also specified, then the XML output method MUST output PUBLIC
followed by the public identifier and then the system identifier; otherwise, it
MUST output SYSTEM
followed by the system identifier. The internal subset MUST be empty. The doctype-public
parameter MUST be ignored unless the doctype-system
parameter is specified.
undeclare-prefixes
ParameterThe Data Model allows an element node that binds a non-empty prefix to have a child element node that does not bind that same prefix. In Namespaces in XML 1.1 ([XML Names 1.1]), this can be represented accurately by undeclaring namespaces. If the undeclare-prefixes
parameter has the value yes
, the output method is XML, and the version
parameter value is
greater than 1.0
, the serializer MUST undeclare namespaces.
Consider an element x:foo
with four in-scope namespaces that associate prefixes with URIs as follows:
x
is associated with http://example.org/x
y
is associated with http://example.org/y
z
is associated with http://example.org/z
xml
is associated with http://www.w3.org/XML/1998/namespace
Suppose that it has a child element x:bar
with three in-scope namespaces:
x
is associated with http://example.org/x
y
is associated with http://example.org/y
xml
is associated with http://www.w3.org/XML/1998/namespace
If namespace undeclaration is in effect, it will be serialized this way:
<x:foo xmlns:x="http://example.org/x" xmlns:y="http://example.org/y" xmlns:z="http://example.org/z"> <x:bar xmlns:z="">...</x:bar> </x:foo>
In Namespaces in XML ([XML Names]), namespace undeclaration is not possible. If the output method is XML, the value of the undeclare-prefixes
parameter is yes
, and the value of the version
parameter is 1.0
, a serialization error [err:SEPM0010] results; the serializer
MUST signal the error.
normalization-form
ParameterThe normalization-form
parameter is applicable to the XML output method. The values NFC
and none
MUST be supported by the serializer. A serialization error [err:SESU0011] results if the value of the normalization-form
parameter specifies a normalization form that is not supported by the
serializer; the serializer MUST signal the error.
It is a serialization error [err:SERE0012] if the value of the parameter is fully-normalized
and any relevant construct of the result begins with a combining character. The serializer MUST signal the error. See Section 2.13 of [XML11] for the definition of the relevant constructs of XML.
media-type
ParameterThe media-type
parameter is applicable to the XML output method. See 3 Serialization Parameters for more information.
use-character-maps
ParameterThe use-character-maps
parameter is applicable to the XML output method. See 9 Character Maps for more information.
byte-order-mark
ParameterThe byte-order-mark
parameter is applicable to the XML output method. See 3 Serialization Parameters for more information.
escape-uri-attributes
ParameterThe escape-uri-attributes
parameter is not applicable to the XML output method. It is the responsibility of the host language to specify whether an error occurs if this parameter is specified in combination with the XML output method, or if the parameter is simply dropped.
include-content-type
ParameterThe include-content-type
parameter is not applicable to the XML output method. It is the responsibility of the host language to specify whether an error occurs if this parameter is specified in combination with the XML output method, or if the parameter is simply dropped.
The XHTML output method serializes the instance of the data model as XML, using the HTML compatibility guidelines defined in the XHTML specification.
It is entirely the responsibility of the person or process that creates the instance of the data model to ensure that the instance of the data model conforms to the [XHTML 1.0] or [XHTML 1.1] specification. It is not an error if the instance of the data model is invalid XHTML. Equally, it is entirely under the control of the person or process that creates the instance of the data model whether the output conforms to XHTML 1.0 Strict, XHTML 1.0 Transitional, or any other specific definition of XHTML.
The serialization of the instance of the data model follows the same rules as for the XML output method, with the general exceptions noted below and parameter-specific exceptions in 6.1 The Influence of Serialization Parameters upon the XHTML Output Method. These differences are based on the HTML compatibility guidelines published in Appendix C of [XHTML 1.0], which are designed to ensure that as far as possible, XHTML is rendered correctly on user agents designed originally to handle HTML.
[Definition: The following XHTML elements have an EMPTY content model: area
, base
, br
, col
, hr
, img
, input
, link
, meta
, basefont
, frame
, isindex
, and param
.] Given an empty instance of an XHTML element whose content model is not EMPTY
(for example, an empty title or paragraph) the serializer MUST NOT use the minimized form. That is, it MUST output <p></p>
and not <p />
.
Given an XHTML element whose content model is EMPTY, the serializer MUST use the minimized tag syntax, for example <br />
, as the alternative syntax <br></br>
allowed by XML gives uncertain results in many existing user agents. The serializer MUST include a space before the trailing
/>
, e.g. <br />
, <hr />
and <img src="karen.jpg" alt="Karen" />
.
The serializer MUST NOT use the entity reference '
which, although legal in XML and therefore in XHTML, is not defined in HTML and is not recognized by all HTML user agents.
The serializer SHOULD output namespace declarations in a way that is consistent with the requirements of the XHTML DTD if this is possible. The XHTML 1.0 DTDs require the declaration xmlns="http://www.w3.org/1999/xhtml"
to appear on the html
element, and only on the html
element. The serializer MUST output namespace declarations that are
consistent with the namespace nodes present in the result tree, but it MUST avoid outputting redundant namespace declarations on elements where the DTD would make them invalid.
Note:
If the html
element is generated by an XSLT literal result element of the form <html xmlns="http://www.w3.org/1999/xhtml"> ... </html>
, or by an XQuery direct element constructor of the same form, then the html
element in the result document will have a node name whose prefix is "", which will satisfy the requirements of the DTD. In other cases the prefix assigned to the element is implementation-dependent.
Note:
Appendix C of [XHTML 1.0] describes a number of compatibility guidelines for users of XHTML who wish to render their XHTML documents with HTML user agents. In some cases, such as the guideline on the form empty elements should take, only the serialization process itself has the ability to follow the guideline. In such cases, those guidelines are reflected in the requirements on the serializer described above.
In all other cases, the guidelines can be adhered to by the instance of the data model that is input to the serialization process. The guideline on the use of whitespace characters in attribute values is one such example. Another example is that xml:lang="..."
does not serialize to both xml:lang="..."
and lang="..."
as required by some legacy user agents. It is the responsibility of the person or process that creates the instance of the data model that is input to
the serialization process to ensure it is created in a way that is consistent with the guidelines. No serialization error results if the input instance of the data model does not adhere to the guidelines.
version
ParameterThe behavior for version
parameter for the XHTML output method is described in 5.1.1 XML Output Method: the version Parameter.
encoding
ParameterThe behavior for encoding
parameter for the XHTML output method is described in 5.1.2 XML Output Method: the encoding Parameter.
indent
ParameterIf the indent
parameter has the value yes
, the serializer MAY add or remove whitespace as it serializes the result tree, so long as it does not change the way that a conforming HTML user agent would render the output.
Note:
This rule can be satisfied by observing the following constraints:
Whitespace MUST NOT be added other than before or after an element, or adjacent to an existing whitespace character.
Whitespace MUST NOT be added or removed adjacent to an inline element. The inline elements are those elements in the XHTML namespace in the %inline category of any of the XHTML 1.0 DTD's, in the %inline.class category of the XHTML 1.1 DTD, and elements in the XHTML namespace with local names ins
and del
if they are used as inline elements (i.e., if they do not contain element children).
Whitespace MUST NOT be added or removed inside a formatted element, the formatted elements being those in the XHTML namespace with local names pre
, script
, style
, and textarea
.
The HTML definition of whitespace is different from the XML definition: see section 9.1 of [HTML] 4.01 specification.
cdata-section-elements
ParameterThe behavior for cdata-section-elements
parameter for the XHTML output method is described in 5.1.4 XML Output Method: the cdata-section-elements Parameter.
omit-xml-declaration
and standalone
ParametersThe behavior for omit-xml-declaration
and standalone
parameters for the XHTML output method is described in 5.1.5 XML Output Method: the omit-xml-declaration and standalone Parameters.
Note:
As with the XML output method, the XHTML output method specifies that an XML declaration will be output unless it is suppressed using the omit-xml-declaration
parameter. Appendix C.1 of [XHTML 1.0] provides advice on the consequences of including, or omitting, the XML declaration.
doctype-system
and doctype-public
ParametersThe behavior for doctype-system
and doctype-public
parameters for the XHTML output method is described in 5.1.6 XML Output Method: the doctype-system and doctype-public Parameters.
undeclare-prefixes
ParameterThe behavior for undeclare-prefixes
parameter for the XHTML output method is described in 5.1.7 XML Output Method: the undeclare-prefixes Parameter.
normalization-form
ParameterThe behavior for normalization-form
parameter for the XHTML output method is described in 5.1.8 XML Output Method: the normalization-form Parameter.
media-type
ParameterThe behavior for media-type
parameter for the XHTML output method is described in 5.1.9 XML Output Method: the media-type Parameter.
use-character-maps
ParameterThe behavior for use-character-maps
parameter for the XHTML output method is described in 5.1.10 XML Output Method: the use-character-maps Parameter.
byte-order-mark
ParameterThe behavior for byte-order-mark
parameter for the XHTML output method is described in 5.1.11 XML Output Method: the byte-order-mark Parameter.
escape-uri-attributes
ParameterIf the escape-uri-attributes
parameter has the value yes
, the XHTML output method MUST apply URI escaping to URI attribute values, except that relative URIs MUST NOT be absolutized.
Note:
This escaping is deliberately confined to non-ASCII characters, because escaping of ASCII characters is not always appropriate, for example when URIs or URI fragments are interpreted locally by the HTML user agent. Even in the case of non-ASCII characters, escaping can sometimes cause problems. More precise control of URI escaping is therefore available by setting escape-uri-attributes
to no
, and controlling the escaping of URIs
by means of the fn:escape-uri
function defined in [XQuery 1.0 and XPath 2.0 Functions and Operators].
include-content-type
ParameterIf the instance of the data model includes a head
element in the XHTML namespace, and the include-content-type
parameter has the value yes
, the XHTML output method MUST add a meta
element as the first child element of the head
element, specifying the character encoding actually used.
For example,
<head> <meta http-equiv="Content-Type" content="text/html; charset=EUC-JP" /> ...
The content type SHOULD be set to the value given for the media-type
parameter.
Note:
It is recommended that the host language use as default value for this parameter one of the MIME types ([RFC2046]) registered for XHTML. Currently, these are text/html
(registered by [RFC2854]) and application/xhtml-xml
(registered by [RFC3236]). Note that some user agents fail to recognize the charset parameter if the content type is not
text/html
.
If a meta
element has been added to the head
element as described above, then any existing meta
element child of the head
element having an http-equiv
attribute with the value "Content-Type", making the comparison without consideration of casing and leading/trailing spaces, MUST be discarded.
Note:
This process removes possible parameters in the attribute value. For example,
<meta http-equiv="Content-Type" content="text/html;version='3.0'" />
in the data model instance would be replaced by,
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
The HTML output method serializes the instance of the data model as HTML.
For example, the following XSL stylesheet generates html output,
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="html" version="4.0"/> <xsl:template match="/"> <html> <xsl:apply-templates/> </html> </xsl:template> ... </xsl:stylesheet>
In the example, the version
attribute of the xsl:output
element indicates the version of the HTML Recommendation [HTML] to which the serialized result is to conform.
It is entirely the responsibility of the person or process that creates the instance of the data model to ensure that the instance of the data model conforms to the HTML Recommendation [HTML]. It is not an error if the instance of the data model is invalid HTML. Equally, it is entirely under the control of the person or process that creates the instance of the data model whether the output conforms to HTML.
The HTML output method MUST NOT output an element differently from the XML output method unless the expanded QName of the element has a null namespace URI. [Definition: An element whose expanded QName has a non-null namespace URI MUST be output as XML. This is known as an XML
Island.] If the expanded QName of the element has a null namespace URI, but the local part of the expanded QName is not recognized as the name of an HTML element, the element MUST be output in the same way as a non-empty, inline element such as span
. In particular:
If the result tree contains namespace nodes for namespaces other than the XML namespace, the HTML output method MUST represent these namespaces using attributes named xmlns
or xmlns:
prefix in the same way as the XML output method would represent them when the version
parameter is set to 1.0
.
If the result tree contains elements or attributes whose names have a non-null namespace URI, the HTML output method MUST generate namespace-prefixed QNames for these nodes in the same way as the XML output method would do when the version
parameter is set to 1.0
.
Where special rules are defined later in this section for serializing specific HTML elements and attributes, these rules MUST NOT be applied to an element or attribute whose name has a non-null namespace URI. However, the generic rules for the HTML output method that apply to all elements and attributes, for example the rules for escaping special characters in the text and the rules for indentation, MUST be used also for namespaced elements and attributes.
When serializing an element whose name is not defined in the HTML specification, but that is in the null namespace, the HTML output method MUST apply the same rules (for example, indentation rules) as when serializing a span
element. The descendants of such an element MUST be serialized as if they were descendants of a span
element.
When serializing an element whose name is in a non-null namespace, the HTML output method MUST apply the same rules (for example, indentation rules) as when serializing a div
element. The descendants of such an element MUST be serialized as if they were descendants of a div
element.
The HTML output method MUST NOT output an end-tag for empty elements. For HTML 4.0, the empty elements are area
, base
, basefont
, br
, col
, frame
, hr
, img
, input
, isindex
, link
, meta
and param
. For example, an element written as <br/>
or <br></br>
in an XSLT stylesheet
MUST be output as <br>
.
The HTML output method MUST recognize the names of HTML elements regardless of case. For example, elements named br
, BR
or Br
MUST all be recognized as the HTML br
element and output without an end-tag.
The HTML output method MUST NOT perform escaping for the content of the script
and style
elements.
For example, a script
element created by an XQuery direct element constructor or an XSLT literal result element, such as:
<script>if (a < b) foo()</script>
or
<script><![CDATA[if (a < b) foo()]]></script>
MUST be output as
<script>if (a < b) foo()</script>
A common requirement is to output a script
element as shown in the example below:
<script type="application/ecmascript"> document.write ("<em>This won't work</em>") </script>
This is illegal HTML, for the reasons explained in section B.3.2 of the [HTML] 4.01 specification. Nevertheless, it is possible to output this fragment, using either of the following constructs:
Firstly, by use of a script
element created by an XQuery direct element constructor or an XSLT literal result element:
<script type="application/ecmascript"> document.write ("<em>This won't work</em>") </script>
Secondly, by constructing the markup from ordinary text characters:
<script type="application/ecmascript"> document.write ("<em>This won't work</em>") </script>
As the [HTML] specification points out, the correct way to write this is to use the escape conventions for the specific scripting language. For JavaScript, it can be written as:
<script type="application/ecmascript"> document.write ("<em>This will work<\/em>") </script>
The [HTML] 4.01 specification also shows examples of how to write this in various other scripting languages. The escaping MUST be done manually, it will not be done by the serializer.
The HTML output method MUST NOT escape "<
" characters occurring in attribute values.
The HTML output method MUST output boolean attributes (that is attributes with only a single allowed value that is equal to the name of the attribute) in minimized form.
For example, a start-tag created using the following XQuery direct element constructor or XSLT literal result element
<OPTION selected="selected">
MUST be output as
<OPTION selected>
The HTML output method MUST NOT escape a &
character occurring in an attribute value immediately followed by a {
character (see Section B.7.1 of the HTML Recommendation [HTML]).
For example, a start-tag created using the following XQuery direct element constructor or XSLT literal result element
<BODY bgcolor='&{{randomrbg}};'>
MUST be output as
<BODY bgcolor='&{randomrbg};'>
See 7.4 The Influence of Serialization Parameters upon the HTML Output Method for additional directives on how attributes may be written.
The HTML output method MAY output a character using a character entity reference in preference to using a numeric character reference, if an entity is defined for the character in the version of HTML that the output method is using. Entity references and character references SHOULD be used only where the character is not present in the selected encoding, or where the visual representation of the character is unclear (as with
, for example).
When outputting a sequence of whitespace characters in the instance of the data model, within an element where whitespace is treated normally (but not in elements such as pre
and textarea
), the HTML output method MAY represent it using any sequence of whitespace that will be treated in the same way by an HTML user agent. See section 3.5 of [XHTML Modularization] for some additional information on handling of whitespace by an
HTML user agent.
Certain characters, specifically the control characters #x7F-#x9F, are legal in XML but not in HTML. It is a serialization error [err:SERE0014] to use the HTML output method when such characters appear in the instance of the data model. The serializer MUST signal the error.
The HTML output method MUST terminate processing instructions with >
rather than ?>
. It is a serialization error [err:SERE0015] to use the HTML output method when >
appears within a processing instruction in the data model instance being serialized.
version
ParameterThe version
attribute indicates the version of the HTML Recommendation [HTML] to which the serialized result is to conform. If the serializer does not support the version of HTML specified by this parameter, it MUST signal a serialization error [err:SESU0013].
encoding
ParameterThe encoding
parameter specifies the encoding to be used. Serializers are REQUIRED to support values of UTF-8
and UTF-16
. A serialization error [err:SESU0007] occurs if an output encoding other than UTF-8
or UTF-16
is requested and the serializer does not support that encoding. The serializer MUST signal the error.
It is possible that the instance of the data model will contain a character that cannot be represented in the encoding that the serializer is using for output. In this case, if the character occurs in a context where HTML recognizes character references, then the character MUST be output as a character entity reference or decimal numeric character reference; otherwise (for example, in a script
or style
element or in
a comment), the serializer MUST signal a serialization error [err:SERE0008].
See 7.4.13 HTML Output Method: the include-content-type Parameter regarding how this parameter is used with the include-content-type
parameter.
indent
ParameterIf the indent
parameter has the value yes
, then the HTML output method MAY add or remove whitespace as it serializes the result tree, so long as it does not change the way that a conforming HTML user agent would render the output.
Note:
This rule can be satisfied by observing the following constraints:
Whitespace MUST NOT be added other than before or after an element, or adjacent to an existing whitespace character.
Whitespace MUST NOT be added or removed adjacent to an inline element. The inline elements are those included in the %inline
category of any of the HTML 4.01 DTD's, as well as the ins
and del
elements if they are used as inline elements (i.e., if they do not contain element children).
Whitespace MUST NOT be added or removed inside a formatted element, the formatted elements being pre
, script
, style
, and textarea
.
Note that the HTML definition of whitespace is different from the XML definition (see section 9.1 of the [HTML] specification).
cdata-section-elements
ParameterThe cdata-section-elements
parameter is not applicable to the HTML output method, except in the case of XML Islands.
omit-xml-declaration
and standalone
ParametersThe omit-xml-declaration
and standalone
parameters are not applicable to the HTML output method.
doctype-system
and doctype-public
ParametersIf the doctype-public
or doctype-system
parameters are specified, then the HTML output method MUST output a document type declaration immediately before the first element. The name following <!DOCTYPE
MUST be HTML
or html
. If the doctype-public
parameter is specified, then the output method MUST output PUBLIC
followed by the specified public identifier; if the
doctype-system
parameter is also specified, it MUST also output the specified system identifier following the public identifier. If the doctype-system
parameter is specified but the doctype-public
parameter is not specified, then the output method MUST output SYSTEM
followed by the specified system identifier.
undeclare-prefixes
ParameterThe undeclare-prefixes
parameter is not applicable to the HTML output method, except in the case of XML Islands.
normalization-form
ParameterThe normalization-form
parameter is applicable to the HTML output method. The values NFC
and none
MUST be supported by the serializer. A serialization error [err:SESU0011] results if the value of the normalization-form
parameter specifies a normalization form that is not supported by the
serializer; the serializer MUST signal the error.
media-type
ParameterThe media-type
parameter is applicable to the HTML output method. See 3 Serialization Parameters for more information. See 7.4.13 HTML Output Method: the include-content-type Parameter regarding how this parameter is used with the include-content-type
parameter.
use-character-maps
ParameterThe use-character-maps
parameter is applicable to the HTML output method. See 9 Character Maps for more information.
byte-order-mark
ParameterThe byte-order-mark
parameter is applicable to the HTML output method. See 3 Serialization Parameters for more information.
escape-uri-attributes
ParameterIf the escape-uri-attributes
parameter has the value yes
, the HTML output method MUST apply URI escaping to URI attribute values, except that relative URIs MUST NOT be absolutized.
Note:
This escaping is deliberately confined to non-ASCII characters, because escaping of ASCII characters is not always appropriate, for example when URIs or URI fragments are interpreted locally by the HTML user agent. Even in the case of non-ASCII characters, escaping can sometimes cause problems. More precise control of URI escaping is therefore available by setting escape-uri-attributes
to no
, and controlling the escaping of URIs
by means of the fn:escape-uri
function defined in [XQuery 1.0 and XPath 2.0 Functions and Operators].
include-content-type
ParameterIf there is a head
element, and the include-content-type
parameter has the value yes
, the HTML output method MUST add a meta
element as the first child element of the head
element specifying the character encoding actually used.
For example,
<HEAD> <META http-equiv="Content-Type" content="text/html; charset=EUC-JP"> ...
The content type MUST be set to the value given for the media-type
parameter.
If a meta
element has been added to the head
element as described above, then any existing meta
element child of the head
element having an http-equiv
attribute with the value "Content-Type" MUST be discarded.
Note:
This process removes possible parameters in the attribute value. For example,
<meta http-equiv="Content-Type" content="text/html;version='3.0'"/>
in the data model instance would be replaced by,
<meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
The Text output method serializes the instance of the data model by outputting the string value of the document node created by sequence normalization, without any escaping.
A newline character in the instance of the data model MAY be output using any character sequence that is conventionally used to represent a line ending in the chosen system environment.
version
ParameterThe version
parameter is not applicable to the Text output method.
encoding
ParameterThe encoding
parameter identifies the encoding that the Text output method MUST use to convert sequences of characters to sequences of bytes. Serializers are REQUIRED to support values of UTF-8
and UTF-16
. A serialization error [err:SESU0007] occurs if the serializer does not support the encoding specified by the encoding
parameter. The serializer MUST signal the error. If the instance of the data model contains a character that cannot be represented in the encoding that the serializer is using for output, the serializer MUST signal a serialization error [err:SERE0008].
indent
ParameterThe indent
parameter is not applicable to the Text output method.
cdata-section-elements
ParameterThe cdata-section-elements
parameter is not applicable to the Text output method.
omit-xml-declaration
and standalone
ParametersThe omit-xml-declaration
and standalone
parameters are not applicable to the Text output method.
doctype-system
and doctype-public
ParametersThe doctype-system
and doctype-public
parameters are not applicable to the Text output method.
undeclare-prefixes
ParameterThe undeclare-prefixes
parameter is not applicable to the Text output method.
normalization-form
ParameterThe normalization-form
parameter is applicable to the Text output method. The values NFC
and none
MUST be supported by the serializer. A serialization error [err:SESU0011] results if the value of the normalization-form
parameter specifies a normalization form that is not supported by the
serializer; the serializer MUST signal the error.
media-type
ParameterThe media-type
parameter is applicable to the Text output method. See 3 Serialization Parameters for more information.
use-character-maps
ParameterThe use-character-maps
parameter is applicable to the Text output method. See 9 Character Maps for more information.
byte-order-mark
ParameterThe byte-order-mark
parameter is applicable to the Text output method. See 3 Serialization Parameters for more information.
The use-character-maps
parameter is a list of characters and corresponding string substitutions.
Character maps allow a specific character appearing in a text or attribute node in the instance of the data model to be replaced with a specified string of characters during serialization. The string that is substituted is output "as is," and the serializer performs no checks that the resulting document is well-formed. This mechanism can therefore be used to introduce arbitrary markup in the serialized output. See Section 20.1 Character MapsXT of [XSL Transformations (XSLT) Version 2.0] for examples of using character mapping in XSLT.
Character mapping is applied to the characters that actually appear in a text or attribute node in the instance of the data model, before any other serialization operations such as escaping or Unicode Normalization are applied. If a character is mapped, then it is not subjected to XML or HTML escaping, nor to Unicode Normalization. The string that is substituted for a character is not validated or processed in any way by the serializer, except for translation into the target encoding. In particular, it is not subjected to XML or HTML escaping, it is not subjected to Unicode Normalization, and it is not subjected to further character mapping.
Character mapping is not applied to characters in text nodes whose parent elements are listed in the cdata-section-elements
parameter, nor to characters for which output escaping has been disabled (disabling output escaping is an [XSL Transformations (XSLT) Version 2.0] feature), nor to characters in attribute values that are subject to URI escaping defined for the HTML and XHTML
output methods, unless URI escaping has been disabled using the escape-uri-attributes
parameter in the output definition.
On serialization, occurrences of a character specified in the use-character-maps
in text nodes and attribute values are replaced by the corresponding string from the use-character-maps
parameter.
Note:
Using a character map can result in non-well-formed documents if the string contains XML-significant characters. For example, it is possible to create documents containing unmatched start and end tags, references to entities that are not declared, or attributes that contain tags or unescaped quotation marks.
If a character is mapped, then it is not subjected to XML or HTML escaping.
A serialization error [err:SERE0008] occurs if character mapping causes the output of a string containing a character that cannot be represented in the encoding that the serializer is using for output. The serializer MUST signal the error.
[Definition: Serialization is intended primarily as a component of a host language such as [XSL Transformations (XSLT) Version 2.0] or [XQuery 1.0: An XML Query Language].] Therefore, this document relies on specifications that use it to specify conformance criteria for Serialization in their respective environments. Specifications that set conformance criteria for their use of Serialization MUST NOT change the semantic definitions of Serialization as given in this specification, except by subsetting and/or compatible extensions. It is the responsibility of the host language to specify how serialization errors should be handled.
Certain facilities in this specification are described as producing implementation-defined results. A claim that asserts conformance with this specification MUST be accompanied by documentation stating the effect of each implementation-defined feature. For convenience, a non-normative checklist of implementation-defined features is provided at D Checklist of Implementation-Defined Features.
It is a error [err:SENR0001] if an item in S6 in sequence normalization is an attribute node or a namespace node.
It is an error if the serializer is unable to satisfy the rules for either a well-formed XML document entity or a well-formed XML external general parsed entity, or both, except for content modified by the character expansion phase of serialization.
It is an error to specify the doctype-system parameter, or to specify the standalone parameter with a value other than omit
, if the instance of the data model contains text nodes or multiple element nodes as children of the root node.
It is an error if the serialized result would contain an NCName Names that contains a character that is not permitted by the version of Namespaces in XML specified by the version
parameter.
It is an error if the serialized result would contain a character that is not permitted by the version of XML specified by the version
parameter.
It is an error if an output encoding other than UTF-8
or UTF-16
is requested and the serializer does not support that encoding.
It is an error if a character that cannot be represented in the encoding that the serializer is using for output appears in a context where character references are not allowed (for example if the character occurs in the name of an element).
It is an error if the omit-xml-declaration
parameter has the value yes
, and the standalone
attribute has a value other than omit
; or the version
parameter has a value other than 1.0
and the doctype-system
parameter is specified.
It is an error if the output method is xml
, the value of the undeclare-prefixes
parameter is yes
, and the value of the version
parameter is 1.0.
It is an error if the value of the normalization-form
parameter specifies a normalization form that is not supported by the serializer.
It is an error if the value of the normalization-form
parameter is fully-normalized
and any relevant construct of the result begins with a combining character.
It is an error if the serializer does not support the version of HTML specified by the version
parameter.
It is an error to use the HTML output method when characters which are legal in XML but not in HTML, specifically the control characters #x7F-#x9F, appear in the instance of the data model.
It is an error to use the HTML output method when >
appears within a processing instruction in the data model instance being serialized.
It is a an error if a parameter value is invalid for the defined domain.
The following list of attributes are declared as type %URI
or %UriList
for a given HTML or XHTML element, with the exception of the name
attribute for element A
which is not a URI type. The name
attribute for element A
should be escaped as is recommended by the HTML Recommendation [HTML] in Appendix B.2.1.
Attributes | Elements |
---|---|
action | FORM |
archive | OBJECT |
background | BODY |
cite | BLOCKQUOTE, DEL, INS, Q |
classid | OBJECT |
codebase | APPLET, OBJECT |
data | OBJECT |
datasrc | BUTTON, DIV, INPUT, OBJECT, SELECT, SPAN, TABLE, TEXTAREA |
for | SCRIPT |
href | A, AREA, BASE, LINK |
longdesc | FRAME, IFRAME, IMG |
name | A |
profile | HEAD |
src | FRAME, IFRAME, IMG, INPUT, SCRIPT |
usemap | IMG, INPUT, OBJECT |
This appendix provides a summary of Serialization features whose effect is explicitly implementation-defined. The conformance rules (see 10 Conformance) require vendors to provide documentation that explains how these choices have been exercised.
method
serialization parameter, then the parameter specifies an implementation-defined output method. (See 3 Serialization Parameters)normalization-form
form parameter is not NFC
, NFD
, NFKC
, NFKD
, fully-normalized
, or none
then the meaning of the value and its effect is implementation-defined. (See 4 Phases of Serialization)This log records the changes that have been made to this document since the second Last Call Draft of 4 April 2005.
bug 1218 - Serialization error codes have been changed from 6 characters to 8 characters. The additional 2 characters are based on a logical categorization of errors as described in the bugzilla report.
bug 1220 - Bullet f in the character expansion phase has been dropped. This bullet describes delimiter fixup when an attribute value contains a quote (or apostrophe). This detail is now left to the implementation.
bug 1222 - A paragraph has been added to section 3 to clarify the support of additional serialization parameters. The names of such parameters must be namespace-qualified and the affect must not override the provisions of this specification.
bug 1258 - A definition of URI attribute values has been added. Appendix List of URI Attributes has also been added to provide a complete list of attributes that are of type %URI or %UriList.
bug 1324 - Description of byte-order-mark in section 3 has been revised to clarify when the parameter is ignored.
bug 1327 - The reference to Section 5.4 of XLink in the description of URI escaping has been removed. It now references the function fn:escape-html-uri defined in XQuery 1.0 and XPath 2.0 Functions and Operators.
bug 1829 - The definition of URI escaping has been modified to add a preceding step to normalize URI attribute values to NFC before applying fn:escape-html-uri.
bug 1859 - The 3rd bullet in section 5.1.3 has been revised and relocated to follow the bulleted list. The constraint that existing whitespace must not be removed without a replacement has been lifted.
internal comment - A paragraph has been added to section 7, describing that it is the person or process responsibility to ensure that the instance of the data model conforms to the HTML Recommendation.
internal comment - The description of error SESU0006 in Appendix B has been modified to reflect the more accurate description of this error provided in section 5.1.1.
bugs 1203, 1204, 1205, 1206, 1221, 1223, 1224, 1332, 1858 - minor editorial changes