You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
635 lines
23 KiB
635 lines
23 KiB
/****************************************************************************
|
|
**
|
|
** Documentation on the xml module
|
|
**
|
|
** Copyright (C) 2005-2008 Trolltech ASA. All rights reserved.
|
|
**
|
|
** This file is part of the Qt GUI Toolkit.
|
|
**
|
|
** This file may be used under the terms of the GNU General
|
|
** Public License versions 2.0 or 3.0 as published by the Free
|
|
** Software Foundation and appearing in the files LICENSE.GPL2
|
|
** and LICENSE.GPL3 included in the packaging of this file.
|
|
** Alternatively you may (at your option) use any later version
|
|
** of the GNU General Public License if such license has been
|
|
** publicly approved by Trolltech ASA (or its successors, if any)
|
|
** and the KDE Free Qt Foundation.
|
|
**
|
|
** Please review the following information to ensure GNU General
|
|
** Public Licensing retquirements will be met:
|
|
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
|
|
** If you are unsure which license is appropriate for your use, please
|
|
** review the following information:
|
|
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
|
|
** or contact the sales department at sales@trolltech.com.
|
|
**
|
|
** This file may be used under the terms of the Q Public License as
|
|
** defined by Trolltech ASA and appearing in the file LICENSE.QPL
|
|
** included in the packaging of this file. Licensees holding valid Qt
|
|
** Commercial licenses may use this file in accordance with the Qt
|
|
** Commercial License Agreement provided with the Software.
|
|
**
|
|
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
|
|
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
|
|
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
|
|
** herein.
|
|
**
|
|
**********************************************************************/
|
|
|
|
/*! \page xml.html
|
|
|
|
\title XML Module
|
|
|
|
\if defined(commercial)
|
|
This module is part of the \link commercialeditions.html Qt Enterprise Edition\endlink.
|
|
\endif
|
|
|
|
\tableofcontents
|
|
|
|
\target overview
|
|
\section1 Overview of the XML architecture in Qt
|
|
|
|
The XML module provides a well-formed XML parser using the SAX2
|
|
(Simple API for XML) interface plus an implementation of the DOM Level
|
|
2 (Document Object Model).
|
|
|
|
SAX is an event-based standard interface for XML parsers.
|
|
The Qt interface follows the design of the SAX2 Java implementation.
|
|
Its naming scheme was adapted to fit the Qt naming conventions.
|
|
Details on SAX2 can be found at
|
|
\link http://www.saxproject.org http://www.saxproject.org \endlink.
|
|
|
|
Support for SAX2 filters and the reader factory are under
|
|
development. The Qt implementation does not include the SAX1
|
|
compatibility classes present in the Java interface.
|
|
|
|
For an introduction to Qt's SAX2 classes see
|
|
"\link #sax2 The Qt SAX2 classes \endlink".
|
|
|
|
DOM Level 2 is a W3C Recommendation for XML interfaces that maps the
|
|
constituents of an XML document to a tree structure. Details and the
|
|
specification of DOM Level 2 can be found at
|
|
\link http://www.w3.org/DOM/ http://www.w3.org/DOM/ \endlink.
|
|
More information about the DOM classes in Qt is provided in the
|
|
\link #dom Qt DOM classes \endlink.
|
|
|
|
|
|
Qt provides the following XML related classes:
|
|
|
|
\table
|
|
\header \i Class \i Short description
|
|
\row \i \l QDomAttr
|
|
\i Represents one attribute of a QDomElement
|
|
\row \i \l QDomCDATASection
|
|
\i Represents an XML CDATA section
|
|
\row \i \l QDomCharacterData
|
|
\i Represents a generic string in the DOM
|
|
\row \i \l QDomComment
|
|
\i Represents an XML comment
|
|
\row \i \l QDomDocument
|
|
\i The representation of an XML document
|
|
\row \i \l QDomDocumentFragment
|
|
\i Tree of QDomNodes which is usually not a complete QDomDocument
|
|
\row \i \l QDomDocumentType
|
|
\i The representation of the DTD in the document tree
|
|
\row \i \l QDomElement
|
|
\i Represents one element in the DOM tree
|
|
\row \i \l QDomEntity
|
|
\i Represents an XML entity
|
|
\row \i \l QDomEntityReference
|
|
\i Represents an XML entity reference
|
|
\row \i \l QDomImplementation
|
|
\i Information about the features of the DOM implementation
|
|
\row \i \l QDomNamedNodeMap
|
|
\i Collection of nodes that can be accessed by name
|
|
\row \i \l QDomNode
|
|
\i The base class for all nodes of the DOM tree
|
|
\row \i \l QDomNodeList
|
|
\i List of QDomNode objects
|
|
\row \i \l QDomNotation
|
|
\i Represents an XML notation
|
|
\row \i \l QDomProcessingInstruction
|
|
\i Represents an XML processing instruction
|
|
\row \i \l QDomText
|
|
\i Represents textual data in the parsed XML document
|
|
\row \i \l QXmlAttributes
|
|
\i XML attributes
|
|
\row \i \l QXmlContentHandler
|
|
\i Interface to report logical content of XML data
|
|
\row \i \l QXmlDeclHandler
|
|
\i Interface to report declaration content of XML data
|
|
\row \i \l QXmlDefaultHandler
|
|
\i Default implementation of all XML handler classes
|
|
\row \i \l QXmlDTDHandler
|
|
\i Interface to report DTD content of XML data
|
|
\row \i \l QXmlEntityResolver
|
|
\i Interface to resolve extern entities contained in XML data
|
|
\row \i \l QXmlErrorHandler
|
|
\i Interface to report errors in XML data
|
|
\row \i \l QXmlInputSource
|
|
\i The input data for the QXmlReader subclasses
|
|
\row \i \l QXmlLexicalHandler
|
|
\i Interface to report lexical content of XML data
|
|
\row \i \l QXmlLocator
|
|
\i The XML handler classes with information about the actual parsing position
|
|
\row \i \l QXmlNamespaceSupport
|
|
\i Helper class for XML readers which want to include namespace support
|
|
\row \i \l QXmlParseException
|
|
\i Used to report errors with the QXmlErrorHandler interface
|
|
\row \i \l QXmlReader
|
|
\i Interface for XML readers (i.e. for SAX2 parsers)
|
|
\row \i \l QXmlSimpleReader
|
|
\i Implementation of a simple XML reader (a SAX2 parser)
|
|
\endtable
|
|
|
|
\target sax2
|
|
\section1 The Qt SAX2 classes
|
|
|
|
\target sax2Intro
|
|
\section2 Introduction to SAX2
|
|
|
|
The SAX2 interface is an event-driven mechanism to provide the user with
|
|
document information. An "event" in this context means something
|
|
reported by the parser, for example, it has encountered a start tag,
|
|
or an end tag, etc.
|
|
|
|
To make it less abstract consider the following example:
|
|
\code
|
|
<quote>A quotation.</quote>
|
|
\endcode
|
|
|
|
Whilst reading (a SAX2 parser is usually referred to as "reader")
|
|
the above document three events would be triggered:
|
|
\list 1
|
|
\i A start tag occurs (\c{<quote>}).
|
|
\i Character data (i.e. text) is found, "A quotation.".
|
|
\i An end tag is parsed (\c{</quote>}).
|
|
\endlist
|
|
|
|
Each time such an event occurs the parser reports it; you can set up
|
|
event handlers to respond to these events.
|
|
|
|
Whilst this is a fast and simple approach to read XML documents,
|
|
manipulation is difficult because data is not stored, simply handled
|
|
and discarded serially. The \link #dom DOM interface
|
|
\endlink reads in and stores the whole document in a tree structure;
|
|
this takes more memory, but makes it easier to manipulate the
|
|
document's structure..
|
|
|
|
The Qt XML module provides an abstract class, \l QXmlReader, that
|
|
defines the interface for potential SAX2 readers. Qt includes a reader
|
|
implementation, \l QXmlSimpleReader, that is easy to adapt through
|
|
subclassing.
|
|
|
|
The reader reports parsing events through special handler classes:
|
|
\table
|
|
\header \i Handler class \i Description
|
|
\row \i \l QXmlContentHandler
|
|
\i Reports events related to the content of a document (e.g. the start tag
|
|
or characters).
|
|
\row \i \l QXmlDTDHandler
|
|
\i Reports events related to the DTD (e.g. notation declarations).
|
|
\row \i \l QXmlErrorHandler
|
|
\i Reports errors or warnings that occurred during parsing.
|
|
\row \i \l QXmlEntityResolver
|
|
\i Reports external entities during parsing and allows users to resolve
|
|
external entities themselves instead of leaving it to the reader.
|
|
\row \i \l QXmlDeclHandler
|
|
\i Reports further DTD related events (e.g. attribute declarations).
|
|
\row \i \l QXmlLexicalHandler
|
|
\i Reports events related to the lexical structure of the
|
|
document (the beginning of the DTD, comments etc.).
|
|
\endtable
|
|
|
|
These classes are abstract classes describing the interface. The \l
|
|
QXmlDefaultHandler class provides a "do nothing" default
|
|
implementation for all of them. Therefore users only need to overload
|
|
the QXmlDefaultHandler functions they are interested in.
|
|
|
|
To read input XML data a special class \l QXmlInputSource is used.
|
|
|
|
Apart from those already mentioned, the following SAX2 support classes
|
|
provide additional useful functionality:
|
|
\table
|
|
\header \i Class \i Description
|
|
\row \i \l QXmlAttributes
|
|
\i Used to pass attributes in a start element event.
|
|
\row \i \l QXmlLocator
|
|
\i Used to obtain the actual parsing position of an event.
|
|
\row \i \l QXmlNamespaceSupport
|
|
\i Used to implement \link xml.html#namespaces namespace\endlink
|
|
support for a reader. Note that namespaces do not change the
|
|
parsing behavior. They are only reported through the handler.
|
|
\endtable
|
|
|
|
|
|
\target sax2Features
|
|
\section2 Features
|
|
|
|
The behaviour of an XML reader depends on its support for certain
|
|
optional features. For example, a reader may have the feature "report
|
|
attributes used for \link xml.html#namespaces namespace\endlink
|
|
declarations and prefixes along with the local name of a tag". Like
|
|
every other feature this has a unique name represented by a URI: it is
|
|
called \e http://xml.org/sax/features/namespace-prefixes.
|
|
|
|
The Qt SAX2 implementation can report whether the reader has
|
|
particular functionality using the \l QXmlReader::hasFeature()
|
|
function. Available features can be tested with QXmlReader::feature(),
|
|
and switched on or off using \l QXmlReader::setFeature().
|
|
|
|
Consider the example
|
|
\code
|
|
<document xmlns:book = 'http://trolltech.com/fnord/book/'
|
|
xmlns = 'http://trolltech.com/fnord/' >
|
|
\endcode
|
|
A reader that does not support the \e
|
|
http://xml.org/sax/features/namespace-prefixes feature would report
|
|
the element name \e document but not its attributes \e xmlns:book and
|
|
\e xmlns with their values. A reader with the feature \e
|
|
http://xml.org/sax/features/namespace-prefixes reports the namespace
|
|
attributes if the \link QXmlReader::feature() feature\endlink is
|
|
switched on.
|
|
|
|
Other features include \e http://xml.org/sax/features/namespace
|
|
(namespace processing, implies \e
|
|
http://xml.org/sax/features/namespace-prefixes) and \e
|
|
http://xml.org/sax/features/validation (the ability to report
|
|
validation errors).
|
|
|
|
Whilst SAX2 leaves it to the user to define and implement whatever
|
|
features are retquired, support for \e
|
|
http://xml.org/sax/features/namespace (and thus \e
|
|
http://xml.org/sax/features/namespace-prefixes) is mandantory.
|
|
The \l QXmlSimpleReader implementation of \l QXmlReader,
|
|
supports them, and can do namespace processing.
|
|
|
|
\l QXmlSimpleReader is not validating, so it
|
|
does not support \e http://xml.org/sax/features/validation.
|
|
|
|
|
|
\target sax2Namespaces
|
|
\section2 Namespace support via features
|
|
|
|
As we have seen in the \link #sax2Features previous section\endlink
|
|
we can configure the behavior of the reader when it comes to namespace
|
|
processing. This is done by setting and unsetting the
|
|
\e http://xml.org/sax/features/namespaces and
|
|
\e http://xml.org/sax/features/namespace-prefixes features.
|
|
|
|
They influence the reporting behavior in the following way:
|
|
\list 1
|
|
\i Namespace prefixes and local parts of elements and attributes can
|
|
be reported.
|
|
\i The qualified names of elements and attributes are reported.
|
|
\i \l QXmlContentHandler::startPrefixMapping() and \l
|
|
QXmlContentHandler::endPrefixMapping() are called by the reader.
|
|
\i Attributes that declare namespaces (i.e. the attribute \e xmlns and
|
|
attributes starting with \e{xmlns:}) are reported.
|
|
\endlist
|
|
|
|
Consider the following element:
|
|
\code
|
|
<author xmlns:fnord = 'http://trolltech.com/fnord/'
|
|
title="Ms"
|
|
fnord:title="Goddess"
|
|
name="Eris Kallisti"/>
|
|
\endcode
|
|
With \e http://xml.org/sax/features/namespace-prefixes set to TRUE
|
|
the reader will report four attributes; but with the \e
|
|
namespace-prefixes feature set to FALSE only three, with the \e
|
|
xmlns:fnord attribute defining a namespace being "invisible" to the
|
|
reader.
|
|
|
|
The \e http://xml.org/sax/features/namespaces feature is responsible
|
|
for reporting local names, namespace prefixes and URIs. With \e
|
|
http://xml.org/sax/features/namespaces set to TRUE the parser will
|
|
report \e title as the local name of the \e fnord:title attribute, \e
|
|
fnord being the namespace prefix and \e http://trolltech.com/fnord/ as
|
|
the namespace URI. When \e http://xml.org/sax/features/namespaces is
|
|
FALSE none of them are reported.
|
|
|
|
In the current implementation the Qt XML classes follow the definition
|
|
that the prefix \e xmlns itself isn't associated with any namespace at all
|
|
(see \link http://www.w3.org/TR/1999/REC-xml-names-19990114/#ns-using
|
|
http://www.w3.org/TR/1999/REC-xml-names-19990114/#ns-using \endlink).
|
|
Therefore even with \e http://xml.org/sax/features/namespaces and
|
|
\e http://xml.org/sax/features/namespace-prefixes both set to TRUE
|
|
the reader won't return either a local name, a namespace prefix or
|
|
a namespace URI for \e xmlns:fnord.
|
|
|
|
This might be changed in the future following the W3C suggestion
|
|
\link http://www.w3.org/2000/xmlns/ http://www.w3.org/2000/xmlns/ \endlink
|
|
to associate \e xmlns with the namespace \e http://www.w3.org/2000/xmlns.
|
|
|
|
|
|
As the SAX2 standard suggests, \l QXmlSimpleReader defaults to having
|
|
\e http://xml.org/sax/features/namespaces set to TRUE and
|
|
\e http://xml.org/sax/features/namespace-prefixes set to FALSE.
|
|
When changing this behavior using \l QXmlSimpleReader::setFeature()
|
|
note that the combination of both features set to
|
|
FALSE is illegal.
|
|
|
|
For a practical demonstration of how the two features affect the
|
|
output of the reader run the \link tagreader-with-features-example.html
|
|
tagreader with features example. \endlink
|
|
|
|
\target sax2NamespacesSummary
|
|
\section3 Summary
|
|
|
|
\l QXmlSimpleReader implements the following behavior:
|
|
|
|
\table
|
|
\header \i (namespaces, namespace-prefixes)
|
|
\i Namespace prefix and local part
|
|
\i Qualified names
|
|
\i Prefix mapping
|
|
\i xmlns attributes
|
|
\row \i (TRUE, FALSE) \i Yes \i Yes* \i Yes \i No
|
|
\row \i (TRUE, TRUE) \i Yes \i Yes \i Yes \i Yes
|
|
\row \i (FALSE, TRUE) \i No* \i Yes \i No* \i Yes
|
|
\row \i (FALSE, FALSE) \i41 Illegal
|
|
\endtable
|
|
|
|
<sup>*</sup> The behavior of these entries is not specified by SAX.
|
|
|
|
\target sax2Properties
|
|
\section2 Properties
|
|
|
|
Properties are a more general concept. They have a unique name,
|
|
represented as an URI, but their value is \c void*. Thus nearly
|
|
anything can be used as a property value. This concept involves some
|
|
danger, though: there is no means of ensuring type-safety; the user
|
|
must take care that they pass the right type. Properties are
|
|
useful if a reader supports special handler classes.
|
|
|
|
The URIs used for features and properties often look like URLs, e.g.
|
|
\c http://xml.org/sax/features/namespace. This does not mean that the
|
|
data retquired is at this address. It is simply a way of defining
|
|
unique names.
|
|
|
|
Anyone can define and use new SAX2 properties for their readers.
|
|
Property support is not mandatory.
|
|
|
|
To set or query properties the following functions are provided: \l
|
|
QXmlReader::setProperty(), \l QXmlReader::property() and \l
|
|
QXmlReader::hasProperty().
|
|
|
|
|
|
\target sax2Reading
|
|
\section2 Further reading
|
|
|
|
More information about XML (e.g. \link xml.html#namespaces namespaces \endlink)
|
|
can be found in the \link xml.html introduction to the Qt XML module. \endlink
|
|
|
|
|
|
|
|
\target dom
|
|
\section1 The Qt DOM classes
|
|
|
|
\target domIntro
|
|
\section2 Introduction to DOM
|
|
|
|
DOM provides an interface to access and change the content and
|
|
structure of an XML file. It makes a hierarchical view of the document
|
|
(a tree view). Thus -- in contrast to the SAX2 interface -- an object
|
|
model of the document is resident in memory after parsing which makes
|
|
manipulation easy.
|
|
|
|
All DOM nodes in the document tree are subclasses of \l QDomNode. The
|
|
document itself is represented as a \l QDomDocument object.
|
|
|
|
Here are the available node classes and their potential child classes:
|
|
|
|
\list
|
|
\i \l QDomDocument: Possible children are
|
|
\list
|
|
\i \l QDomElement (at most one)
|
|
\i \l QDomProcessingInstruction
|
|
\i \l QDomComment
|
|
\i \l QDomDocumentType
|
|
\endlist
|
|
\i \l QDomDocumentFragment: Possible children are
|
|
\list
|
|
\i \l QDomElement
|
|
\i \l QDomProcessingInstruction
|
|
\i \l QDomComment
|
|
\i \l QDomText
|
|
\i \l QDomCDATASection
|
|
\i \l QDomEntityReference
|
|
\endlist
|
|
\i \l QDomDocumentType: No children
|
|
\i \l QDomEntityReference: Possible children are
|
|
\list
|
|
\i \l QDomElement
|
|
\i \l QDomProcessingInstruction
|
|
\i \l QDomComment
|
|
\i \l QDomText
|
|
\i \l QDomCDATASection
|
|
\i \l QDomEntityReference
|
|
\endlist
|
|
\i \l QDomElement: Possible children are
|
|
\list
|
|
\i \l QDomElement
|
|
\i \l QDomText
|
|
\i \l QDomComment
|
|
\i \l QDomProcessingInstruction
|
|
\i \l QDomCDATASection
|
|
\i \l QDomEntityReference
|
|
\endlist
|
|
\i \l QDomAttr: Possible children are
|
|
\list
|
|
\i \l QDomText
|
|
\i \l QDomEntityReference
|
|
\endlist
|
|
\i \l QDomProcessingInstruction: No children
|
|
\i \l QDomComment: No children
|
|
\i \l QDomText: No children
|
|
\i \l QDomCDATASection: No children
|
|
\i \l QDomEntity: Possible children are
|
|
\list
|
|
\i \l QDomElement
|
|
\i \l QDomProcessingInstruction
|
|
\i \l QDomComment
|
|
\i \l QDomText
|
|
\i \l QDomCDATASection
|
|
\i \l QDomEntityReference
|
|
\endlist
|
|
\i \l QDomNotation: No children
|
|
\endlist
|
|
|
|
With \l QDomNodeList and \l QDomNamedNodeMap two collection classes
|
|
are provided: \l QDomNodeList is a list of nodes,
|
|
and \l QDomNamedNodeMap is used to handle unordered sets of nodes
|
|
(often used for attributes).
|
|
|
|
The \l QDomImplementation class allows the user to query features of the
|
|
DOM implementation.
|
|
|
|
\section2 Further reading
|
|
|
|
To get started please refer to the \l QDomDocument documentation.
|
|
|
|
\target namespaces
|
|
\section1 An introduction to namespaces
|
|
|
|
Parts of the Qt XML module documentation assume that you are familiar
|
|
with XML namespaces. Here we present a brief introduction; skip to
|
|
\link #namespacesConventions Qt XML documentation conventions \endlink
|
|
if you already know this material.
|
|
|
|
Namespaces are a concept introduced into XML to allow a more modular
|
|
design. With their help data processing software can easily resolve
|
|
naming conflicts in XML documents.
|
|
|
|
Consider the following example:
|
|
|
|
\code
|
|
<document>
|
|
<book>
|
|
<title>Practical XML</title>
|
|
<author title="Ms" name="Eris Kallisti"/>
|
|
<chapter>
|
|
<title>A Namespace Called fnord</title>
|
|
</chapter>
|
|
</book>
|
|
</document>
|
|
\endcode
|
|
|
|
Here we find three different uses of the name \e title. If you wish to
|
|
process this document you will encounter problems because each of the
|
|
\e titles should be displayed in a different manner -- even though
|
|
they have the same name.
|
|
|
|
The solution would be to have some means of identifying the first
|
|
occurrence of \e title as the title of a book, i.e. to use the \e
|
|
title element of a book namespace to distinguish it from, for example,
|
|
the chapter title, e.g.:
|
|
\code
|
|
<book:title>Practical XML</book:title>
|
|
\endcode
|
|
|
|
\e book in this case is a \e prefix denoting the namespace.
|
|
|
|
Before we can apply a namespace to element or attribute names we must
|
|
declare it.
|
|
|
|
Namespaces are URIs like \e http://trolltech.com/fnord/book/. This
|
|
does not mean that data must be available at this address; the URI is
|
|
simply used to provide a unique name.
|
|
|
|
We declare namespaces in the same way as attributes; strictly speaking
|
|
they \e are attributes. To make for example \e
|
|
http://trolltech.com/fnord/ the document's default XML namespace \e
|
|
xmlns we write
|
|
|
|
\code
|
|
xmlns="http://trolltech.com/fnord/"
|
|
\endcode
|
|
|
|
To distinguish the \e http://trolltech.com/fnord/book/ namespace from
|
|
the default, we must supply it with a prefix:
|
|
|
|
\code
|
|
xmlns:book="http://trolltech.com/fnord/book/"
|
|
\endcode
|
|
|
|
A namespace that is declared like this can be applied to element and
|
|
attribute names by prepending the appropriate prefix and a ":"
|
|
delimiter. We have already seen this with the \e book:title element.
|
|
|
|
Element names without a prefix belong to the default namespace. This
|
|
rule does not apply to attributes: an attribute without a prefix does
|
|
not belong to any of the declared XML namespaces at all. Attributes
|
|
always belong to the "traditional" namespace of the element in which
|
|
they appear. A "traditional" namespace is not an XML namespace, it
|
|
simply means that all attribute names belonging to one element must be
|
|
different. Later we will see how to assign an XML namespace to an
|
|
attribute.
|
|
|
|
Due to the fact that attributes without prefixes are not in any XML
|
|
namespace there is no collision between the attribute \e title (that
|
|
belongs to the \e author element) and for example the \e title element
|
|
within a \e chapter.
|
|
|
|
Let's clarify this with an example:
|
|
\code
|
|
<document xmlns:book = 'http://trolltech.com/fnord/book/'
|
|
xmlns = 'http://trolltech.com/fnord/' >
|
|
<book>
|
|
<book:title>Practical XML</book:title>
|
|
<book:author xmlns:fnord = 'http://trolltech.com/fnord/'
|
|
title="Ms"
|
|
fnord:title="Goddess"
|
|
name="Eris Kallisti"/>
|
|
<chapter>
|
|
<title>A Namespace Called fnord</title>
|
|
</chapter>
|
|
</book>
|
|
</document>
|
|
\endcode
|
|
|
|
Within the \e document element we have two namespaces declared. The
|
|
default namespace \e http://trolltech.com/fnord/ applies to the \e
|
|
book element, the \e chapter element, the appropriate \e title element
|
|
and of course to \e document itself.
|
|
|
|
The \e book:author and \e book:title elements belong to the namespace
|
|
with the URI \e http://trolltech.com/fnord/book/.
|
|
|
|
The two \e book:author attributes \e title and \e name have no XML
|
|
namespace assigned. They are only members of the "traditional"
|
|
namespace of the element \e book:author, meaning that for example two
|
|
\e title attributes in \e book:author are forbidden.
|
|
|
|
In the above example we circumvent the last rule by adding a \e title
|
|
attribute from the \e http://trolltech.com/fnord/ namespace to \e
|
|
book:author: the \e fnord:title comes from the namespace with the
|
|
prefix \e fnord that is declared in the \e book:author element.
|
|
|
|
Clearly the \e fnord namespace has the same namespace URI as the
|
|
default namespace. So why didn't we simply use the default namespace
|
|
we'd already declared? The answer is quite complex:
|
|
\list
|
|
\i attributes without a prefix don't belong to any XML namespace at
|
|
all, not even to the default namespace;
|
|
\i additionally omitting the prefix would lead to a \e title-title clash;
|
|
\i writing it as \e xmlns:title would declare a new namespace with the
|
|
prefix \e title instead of applying the default \e xmlns namespace.
|
|
\endlist
|
|
|
|
With the Qt XML classes elements and attributes can be accessed in two
|
|
ways: either by refering to their qualified names consisting of the
|
|
namespace prefix and the "real" name (or \e local name) or by the
|
|
combination of local name and namespace URI.
|
|
|
|
More information on XML namespaces can be found at
|
|
\l http://www.w3.org/TR/REC-xml-names/.
|
|
|
|
|
|
\target namespacesConventions
|
|
\section2 Conventions used in Qt XML documentation
|
|
|
|
The following terms are used to distinguish the parts of names within
|
|
the context of namespaces:
|
|
\list
|
|
\i The \e {qualified name}
|
|
is the name as it appears in the document. (In the above example \e
|
|
book:title is a qualified name.)
|
|
\i A \e {namespace prefix} in a qualified name
|
|
is the part to the left of the ":". (\e book is the namespace prefix in
|
|
\e book:title.)
|
|
\i The \e {local part} of a name (also refered to as the \e {local
|
|
name}) appears to the right of the ":". (Thus \e title is the
|
|
local part of \e book:title.)
|
|
\i The \e {namespace URI} ("Uniform Resource Identifier") is a unique
|
|
identifier for a namespace. It looks like a URL
|
|
(e.g. \e http://trolltech.com/fnord/ ) but does not retquire
|
|
data to be accessible by the given protocol at the named address.
|
|
\endlist
|
|
|
|
Elements without a ":" (like \e chapter in the example) do not have a
|
|
namespace prefix. In this case the local part and the qualified name
|
|
are identical (i.e. \e chapter).
|
|
*/
|