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<concept id="GUID-F79E4F18-19E2-577E-8409-8B82BD48AC66" xml:lang="en"><title>XML

Framework Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The XML Framework is a collection of components for event-based XML parsing

and provides content-processing architecture. </p>

<section><title>Purpose</title> <p>The XML Framework provides configurable

features for parsing XML and <xref href="http://www.w3.org/TR/wbxml/" scope="external">WBXML</xref> (WAP

Binary XML), with options for validating against a specification and auto-correcting

for spelling errors in the validated text, using a single interface. It is

based on the <xref href="http://www.saxproject.org" scope="external">SAX</xref> (Simple

API for XML) specification. </p> </section>

<section><title>Required background</title> <p>You must have a basic understanding

on XML before using XML Framework. </p> </section>

<section><title>Key concepts</title> <p>The following are the key concepts

of XML Framework: </p><p><b>Attribute</b></p><p>A name-value pair separated

by an equals sign, for example <codeph>author="Jane Austen"</codeph>  </p><p><b>Attribute

type </b></p><p>One of certain data types defined for attributes, for instance <codeph>CDATA</codeph>. </p><p><b>Client</b></p><p>An

application which uses the XML framework for parsing or generating a document. </p><p><b>Document

Type Definition (DTD) </b></p><p>A document which defines a particular use

of XML entities (the names, attributes and values permitted). </p><p><b>Extension</b></p><p>WBXML

extends XML syntax with extension tokens which are used differently by different

applications. For example, extension token is used to refer to a string table

created specifically for each message and transmitted in the introduction

of the message. </p><p><b>Parser</b></p><p>It is an interface to the XML framework

which allows a client to access the parser plug-ins, which are specific for

a mark-up language. For example, XML Expat Parser and WBXML Parser. </p><p><b>String

dictionary collection</b></p><p>A class that holds a collection of string

dictionaries. </p><p><b>String dictionary plug-ins </b></p><p>The XML Framework

allows strings to be stored in DTD document, XML namespace or WBXML code page

in an ECOM plug-in that could be accessed as required by the parser and the

client. These plug-ins are referred as string dictionary plug-ins. </p><p><b>String

pool</b></p><p>A string pool is a mechanism for storing strings in a particular

way using which the strings can be compared quickly. </p><p><b>String table</b></p><p>A

WBXML document is encoded and decoded using a table of frequently encountered

strings which the body of the document references by index to compress the

data. </p><p><b>Uniform Resource Identifier (URI)</b></p><p>The web address

associated with a prefix. For instance, <codeph>http://www.w3.org/XML/1998/namespace</codeph>. </p><p><b>WBXML</b></p><p>WAP

Binary XML (WBXML) is a binary representation of XML. It was developed by

the Open Mobile Alliance as a standard to allow XML documents to be transmitted

in a compact manner over mobile networks and was proposed as an addition to

the World Wide Web Consortium's Wireless Application Protocol family of standards. </p> </section>

<section><title>Architecture</title> <p>The following diagram illustrates

the XML framework, consisting of client and a parser: </p> <fig id="GUID-9EE24AE6-17F1-59A2-9AF8-9A1068393053">

<title>              Block diagram of XML framework            </title>

<image href="GUID-CA1CE18E-DB40-5608-BE09-3767FB094AB2_d0e691341_href.png" placement="inline"/>

</fig> <p>The XML framework consists of classes which model the main constituents

of the architecture - the framework as a whole, the parser plug-ins and extensions

to XML, the content processor chain and the content handler mechanism. </p> <p>The

XML and WBXML parsers convert the contents of a document to UTF-8 format.

This is to ensure that extended characters are not lost from the document

by the String Pool. Expat is the engine behind the XML parser plug-in. </p> <p>The

XML Framework allows strings to be stored for a particular DTD, XML namespace

or WBXML codepage in an ECOM plug-in that can be accessed when requireded

by the Parser and the Client. These plug-ins are referred as String Dictionary

Plug-ins and they are managed through a string dictionary collection object.

See <xref href="GUID-0D16866C-F46B-5A2B-B974-324278588A1B.dita">String Dictionary</xref>  </p> <p>Libxml2

provides XML processing, parsing and validation APIs. See <xref href="GUID-0129AE17-B171-5CD5-8542-1DB738CBAB8B.dita">libxml2</xref>. </p> <p>Plug-in

1 and Plug-in 2 are examples of optional processors, which may be chained

together with the parser output to allow further processing of the data, before

the client receives it. Such plug-ins can be a DTD validator or a document

auto-corrector. The chain is not limited to just two plug-ins. </p> <p><b>Parser

framework</b> </p> <p>The XML framework contains Parser framework which is

represented by the <xref href="GUID-3C824E3B-68AB-31C5-A3D7-26A73B53D076.dita"><apiname>CParser</apiname></xref> class. A client with an XML

document to be parsed creates a <xref href="GUID-3C824E3B-68AB-31C5-A3D7-26A73B53D076.dita"><apiname>CParser</apiname></xref> object and calls

its parse functions. <xref href="GUID-3C824E3B-68AB-31C5-A3D7-26A73B53D076.dita"><apiname>CParser</apiname></xref> obtains the data about plug-ins

and the document to be parsed from<xref href="GUID-A6CF939C-110C-3FA4-8C2E-0B48C04D9CFB.dita"><apiname>CMatchData</apiname></xref> and <xref href="GUID-D79A2F59-8DC1-3493-92F6-2E1337CD9405.dita"><apiname>RDocumentParameters</apiname></xref> classes

respectively. </p> <p>The parser framework conforms to the event-based SAX

specification. It outputs an event when it starts or finishes reading one

of the following: </p> <ul>

<li id="GUID-A229D260-A15A-5EC6-8808-60577D988073"><p>a document </p> </li>

<li id="GUID-4ED3BF2E-0CB8-54E3-B332-C60A032FD8F5"><p>a start tag </p> </li>

<li id="GUID-57CB6A28-6F7B-5D75-AB59-BA4429374D23"><p>an end tag </p> </li>

<li id="GUID-2CB3BFDA-425D-5936-B2D0-1A5459D56813"><p>a prefix mapping </p> </li>

<li id="GUID-181F5F9F-D9D2-5E42-96F4-BACD64B2ABBF"><p>a processing instruction </p> </li>

<li id="GUID-FB122F10-A946-5661-8A9B-A42877FB0DAC"><p>character data </p> </li>

<li id="GUID-C0C9C2C4-862B-55CF-904F-E761518275DB"><p>ignorable white space </p> </li>

</ul> <p>For more information on XML-related concepts, refer to W3C or similar

sources. </p> <p><b>Parser plug-ins</b> </p> <p>The <xref href="GUID-3C824E3B-68AB-31C5-A3D7-26A73B53D076.dita"><apiname>CParser</apiname></xref> is

the interface to the XML framework allowing the client to access the parser

plug-ins, each one of which is specific to a mark-up language (e.g. XML, WBXML).

Individual parser plug-in implements the <xref href="GUID-6F334B00-8026-3FA3-AE96-B0A511030B7B.dita"><apiname>MParser</apiname></xref> interface.

It is associated through the <xref href="GUID-5F929E9F-E895-3DA6-8072-28C4B8B1CF81.dita"><apiname>TParserInitParams</apiname></xref> class, with

a character set converter (to convert other formats to Unicode), a string

dictionary and an element stack. </p> <p>The Symbian platform framework is

delivered with three parser plug-ins, two for XML and one for WBXML. </p> <ul>

<li id="GUID-CAAD5966-F37D-5A9C-A240-911B6683B315"><p>The first XML parser

consists of <xref href="GUID-278C5360-5023-3406-98B1-BEB7AD2A4A9D.dita"><apiname>CXmlParser</apiname></xref> class, which is wrapped around the <xref href="GUID-D7864E56-D87D-3EC0-BA5F-804BE8F532FF.dita"><apiname>CExpat</apiname></xref> class,

an implementation of the stream-based Expat parser. </p> </li>

<li id="GUID-4A7DAA35-DD92-547F-BF81-232521F21A79"><p>The second XML parser

consists of <xref href="GUID-F6E8B374-12D7-34FE-A1AA-F8B2BCA45B0A.dita"><apiname>CXMLEngineSAXPlugin</apiname></xref> class, which encapsulates

the SAX parser of the <codeph>libxml2</codeph> component. It is not available

if the Symbian platform build excludes this component. </p> </li>

<li id="GUID-A5342749-34E7-5AD4-A5E4-FD46703F4AC7"><p>The WBXML parser is

implemented as the <xref href="GUID-98F7BF57-BDC8-3BA4-9141-7DEDFFF64DB0.dita"><apiname>CWmxmlParser</apiname></xref> class. </p> </li>

</ul> <p><b>Extensions to XML</b> </p> <p>The XML framework provides extensions

to XML. At present WBXML is implemented. WBXML requires use of string dictionaries

and extension tokens to store the element strings specific to the WBXML, which

are represented by the <xref href="GUID-094A4884-182E-3A10-80F5-85A925020BC1.dita"><apiname>RStringDictionaryCollection</apiname></xref>, <xref href="GUID-FF04F0FE-771D-3197-BA3F-BB34C78E2F65.dita"><apiname>MWbxmlExtensionHandler</apiname></xref> and <xref href="GUID-1D0F59D7-574C-3485-9AB7-499712E5F20B.dita"><apiname>TExtensionTokens</apiname></xref> classes. </p> <p><b>Content processors</b> </p> <p>Content processors are

plug-ins which perform further operations on the output of a parser plug-in.

They implement the <xref href="GUID-7942EDC6-6571-3423-8ECA-D3DB68A78CB6.dita"><apiname>MContentProcessor</apiname></xref> interface and are

associated through the <xref href="GUID-892978EC-1BE4-3356-ADB1-1E7EAB83C686.dita"><apiname>TContentProcessorInitParams</apiname></xref> class,

with a string dictionary and element stack. They are organised into chains

by the <xref href="GUID-0DFBB9EA-5A0E-3B4F-AD60-3CCD35090B40.dita"><apiname>MContentSource</apiname></xref> class which directs the output of

each plug-in to the next plug-in in the chain. </p> <p><b>Content handlers</b> </p> <p>A

client application which is designed to react to the output of the XML framework

event must implement the <xref href="GUID-A6B8386B-29F6-3BEC-9D77-D8E0900DEAC2.dita"><apiname>MContentHandler</apiname></xref> interface. The

functions to be implemented correspond to the SAX specification discussed

in the Parser Framework section. </p> </section>

<section><title>APIs</title> <p>The XML Framework exports the following APIs: </p> <table id="GUID-7EBF7AA5-B11F-5C40-93A7-685E8714DE92">

<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

<thead>

<row>

<entry>API</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><p> <xref href="GUID-D7864E56-D87D-3EC0-BA5F-804BE8F532FF.dita"><apiname>CExpat</apiname></xref>  </p> </entry>

<entry><p>Encapsulates the Expat XML parser. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-278C5360-5023-3406-98B1-BEB7AD2A4A9D.dita"><apiname>CXmlParser</apiname></xref>  </p> </entry>

<entry><p>Implementation of the stream-based Expat parser. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-F6E8B374-12D7-34FE-A1AA-F8B2BCA45B0A.dita"><apiname>CXMLEngineSAXPlugin</apiname></xref>  </p> </entry>

<entry><p>Encapsulates the SAX parser of the <codeph>libxml2</codeph> component. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-3C824E3B-68AB-31C5-A3D7-26A73B53D076.dita"><apiname>CParser</apiname></xref>  </p> </entry>

<entry><p>Represents the entire parser framework. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-A6CF939C-110C-3FA4-8C2E-0B48C04D9CFB.dita"><apiname>CMatchData</apiname></xref>  </p> </entry>

<entry><p>Consists of the data of the plug-ins. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-98F7BF57-BDC8-3BA4-9141-7DEDFFF64DB0.dita"><apiname>CWmxmlParser</apiname></xref>  </p> </entry>

<entry><p>WBXML parser implementation. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-D79A2F59-8DC1-3493-92F6-2E1337CD9405.dita"><apiname>RDocumentParameters</apiname></xref>  </p> </entry>

<entry><p>Consists of the data about the document to be parsed. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-AE53784D-B405-34D8-9A93-ACDE6F8ECA44.dita"><apiname>RElementStack</apiname></xref>  </p> </entry>

<entry><p>Data structure used to store XML elements and check the tag ordering. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-094A4884-182E-3A10-80F5-85A925020BC1.dita"><apiname>RStringDictionaryCollection</apiname></xref>  </p> </entry>

<entry><p>Holds a collection of dictionaries requested by the user. </p> </entry>

</row>

</tbody>

</tgroup>

</table> </section>

<section><title>Typical uses</title> <p>The following tasks can be performed

using XML Framework: </p> <ul>

<li id="GUID-0FD3D44F-83D3-57C4-9C3E-063450A8078E"><p>Parsing an XML document. </p> </li>

<li id="GUID-9C4511A4-49FE-53FA-83A4-9B55D58B0905"><p>Choosing a parser plug-in. </p> </li>

<li id="GUID-6B09BFFF-8BBC-5FDC-B1CE-339C893C5164"><p>Using content processor. </p> </li>

<li id="GUID-EC907C49-599B-5C60-B212-74AB22DEA759"><p>Writing a parser plug-in. </p> </li>

<li id="GUID-A86A66BB-0C80-5760-B7C3-7C4E276C5EFF"><p>Customising a parser

plug-in. </p> </li>

<li id="GUID-3F689A67-D8DC-50EF-9D49-476417E503B6"><p>Creating a resource

file for a parser plug-in. </p> </li>

</ul> </section>

</conbody><related-links>

<link href="GUID-4A9255D1-42A4-57FA-A4B4-42C552964047.dita"><linktext>XML Framework

Tutorials</linktext></link>

</related-links></concept>