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 <p><span class="title">Analyzing XML schemas with the Schema
 Infoset Model</span></p>

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 <td align="middle" background="images/../dwtip1/bg-gold.gif"
 height="5"><b>Contents:</b></td>
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 <td><a href="#h1">Example: Analyzing schemas</a></td>
 </tr>

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 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
 </tr>

 <tr>
 <td><a href="#h2">Loading schemas</a></td>
 </tr>

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 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
 </tr>

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 <td><a href="#h3">Convenient schema querying</a></td>
 </tr>

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 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
 </tr>

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 <td><a href="#h4">Schema components model</a></td>
 </tr>

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 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
 </tr>

 <tr>
 <td><a href="#h5">Your report: Types missing max/min
 facets</a></td>
 </tr>

 <tr>
 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
 </tr>

 <tr>
 <td><a href="#conclusion">Conclusion</a></td>
 </tr>

 <tr>
 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
 </tr>

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 <td><a href="#samplecode">Sample code</a></td>
 </tr>

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 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
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 <!--Standard links for every article-->
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 <td><a href="#resources">Resources</a></td>
 </tr>

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 <td height="1"><img height="5" alt="" src="images/../dwtip1/c.gif"
 width="160" /></td>
 </tr>

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 <td><a href="#author1">About the author</a></td>
 </tr>

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 <p><span class="atitle2">Easily perform complex queries on your
 schemas with this model</span></p>

 <table cellspacing="0" cellpadding="0" border="0">
 <tbody>
 <tr valign="top" align="left">
 <td>
 <p>Level: Intermediate</p>
 </td>
 </tr>
 </tbody>
 </table>

 <p><a href="#author1">Shane Curcuru</a> (<a
 href="mailto:shane_curcuru@us.ibm.com">shane_curcuru@us.ibm.com</a>)<br />

 Advisory Software Engineer, IBM<br />
 July 2002</p>

 <blockquote>As the use of schemas grows, the need for tools to
 manipulate schemas grows. The new Schema Infoset Model provides a
 complete modeling of schemas themselves, including the concrete
 representations as well as the abstract relationships within a
 schema or a set of schemas. This article will show some of the
 power of this library to easily query the model of a schema for
 detailed information about it; we could also update the schema to
 fix any problems found and write the schema back out.</blockquote>

 <p style="font-style: italic"><b>Note:</b> This tip assumes you
 have a basic knowledge of schema documents; there are a number of
 links to schema documentation and a tutorial in <a
 href="#resources">Resources</a>.</p>

 <p>Although there are a number of parsers and tools that use
 schemas to validate or analyze XML documents, tools that allow
 querying and advanced manipulation of schema documents themselves
 are still being built. The Schema Infoset Model (AKA
 org.eclipse.xsd.*, or just "the library") provides a rich API
 library that models schemas -- both their concrete representations
 (perhaps in a schema.xsd file) and the abstract concepts in a
 schema as defined by the specification. As anyone who has read the
 schema specs knows, they're quite detailed, and this model strives
 to expose all the details within any schema. This will then allow
 you to efficiently manage your schema collection, and empower
 higher level schema tools -- perhaps schema-aware parsers and
 transformers.</p>

 <table cellspacing="0" cellpadding="5" width="50%" align="right"
 border="1">
 <tbody>
 <tr>
 <td background="images/../dwtip1/bg-gold.gif"><a id="sidebar"
 name="sidebar"><b>Schema Infoset Model UML diagrams</b></a><br />


 <p>The library includes various UML diagrams for the actual library
 classes, which gives a quick overview of the relationships and
 attributes of common schema components.</p>

 <p><b>Abstract Schema Component relationships</b><br />
 <a href="images/../dwtip1/Relations.gif">This diagram</a> shows the
 relations between Schema Infoset Components -- the abstract
 relationships between schema objects as modeled in the library.
 Black diamonds show strong composition or aggregation; open
 diamonds show weak aggregation.</p>

 <p><b>Abstract Schema Component attributes</b><br />
 <a href="images/../dwtip1/Attributes.gif">This diagram</a> shows
 some of the attributes of the abstract schema components as modeled
 in the library, as well as part of the class hierarchy.</p>

 <p><b>Schema Library class listing</b><br />
 <a
 href="../../../references/articles/dwtip1-scpw/sidebar-listing.html">
 This listing</a> shows the core classes included in
 org.eclipse.xsd.</p>

 <p>These diagrams are included in the library's documentation,
 including several other UML diagrams for both the abstract and
 concrete class trees.</p>
 </td>
 </tr>
 </tbody>
 </table>

 <p>For an interface listing of the library showing all the schema
 objects modeled, please see <a href="#sidebar">Schema Infoset Model
 UML diagrams</a>. The library also includes the UML diagrams used
 in building the library interfaces themselves; these diagrams show
 the relationships between the library objects, which very closely
 mimic the concepts in the schema specifications.</p>

 <p><a id="h1" name="h1"><span class="atitle2">Example: Analyzing
 your schemas</span></a><br />
 In this example, you'll want to check your schema for possibly
 failing to specify restrictions on integer-derived types. This
 could be useful for ensuring that all order quantities in purchase
 orders have been bounded. Here, the schemas must be very specific,
 so you want to require that all simple types that derive from
 integers include both min/maxInclusive or min/maxExclusive facets.
 However, if the min/maxInclusive or min/maxExclusive facets are
 inherited from a type which this type derives from, that is still
 sufficient.</p>

 <p>While you can use XSLT or XPath to query a schema's concrete
 representation in an <code>.xsd</code> file or inside some other
 <code>.xml</code> content, it is much more difficult to discover
 the type derivations and interrelationships that schema components
 actually have. Since the Schema Infoset Model library models both
 the concrete representation and the abstract concept of the schema,
 it can easily be used to collect details about its components, even
 when the schema may have deep type hierarchies or be defined in
 multiple schema files.</p>

 <p>In this simple schema, you will find some types that meet the
 criteria of having max/min facets, and some that do not. (You can
 find the full schema in FindTypesMissingFacets.xsd included in the
 <a href="images/../dwtip1/xsdqcode.zip">zip file</a>.)</p>

 <a id="code1" name="code1"><b>Listing 1. Sample schema</b></a>

 <table cellspacing="0" cellpadding="5" width="100%"
 bgcolor="#cccccc" border="1">
 <tbody>
 <tr>
 <td>
 <pre>
 <code>&lt;xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
 targetNamespace="http://www.research.ibm.com/XML/NS/xsd"
 xmlns="http://www.research.ibm.com/XML/NS/xsd"&gt;

 &lt;!-- SimpleType missing both max/min facets --&gt;
 &lt;xsd:simpleType name="integer-noFacets"&gt;
     &lt;xsd:restriction base="xsd:integer"/&gt;
 &lt;/xsd:simpleType&gt;

 &lt;!-- Derived type has inherited min facet but missing max facet --&gt;
 &lt;xsd:simpleType name="<span
 class="boldcode">positiveInteger-inheritedMinFacet</span>"&gt;
     &lt;xsd:restriction base="xsd:positiveInteger"/&gt;
 &lt;/xsd:simpleType&gt;

 &lt;!-- Derived type with both effective max/min facets --&gt;
 &lt;xsd:simpleType name="positiveInteger-bothFacets"&gt;
     &lt;xsd:restriction base="<span
 class="boldcode">positiveInteger-inheritedMinFacet</span>"&gt;
         &lt;xsd:maxExclusive value="100"/&gt;
     &lt;/xsd:restriction&gt;
 &lt;/xsd:simpleType&gt;
 &lt;!-- etc... --&gt;
 &lt;/xsd:schema&gt;
 </code>
 </pre>
 </td>
 </tr>
 </tbody>
 </table>

 <p><a id="h2" name="h2"><span class="atitle2">Loading schemas into
 the library</span></a><br />
 The library can read and write schema objects from a variety of
 sources. I'll show it using the org.eclipse.emf ResourceSet
 framework to easily load sets of schemas; you can also build and
 emit schemas directly from or to a DOM object that you manage
 yourself. The library provides a custom <code>XSDResourceSet</code>
 implementation that can intelligently and automatically load sets
 of schemas related by includes, imports, and redefines. The
 abstract relationship between related schemas is also modeled in
 the library.</p>

 <a id="code2" name="code2"><b>Listing 2. Loading a schema</b></a>

 <table cellspacing="0" cellpadding="5" width="100%"
 bgcolor="#cccccc" border="1">
 <tbody>
 <tr>
 <td>
 <pre>
 <code>// String variable schemaURL is "FindTypesMissingFacets.xsd" or the URL to your schema
 // Create a resource set and load the main schema file into it.
 ResourceSet resourceSet = new ResourceSetImpl();
 XSDResourceImpl xsdSchemaResource = (XSDResourceImpl)resourceSet.getResource(
         URI.createDeviceURI(schemaURL), true);

 // getResources() returns an iterator over all the resources, therefore, the main resource
 // and those that have been included, imported, or redefined.
 for (Iterator resources = resourceSet.getResources().iterator();
     resources.hasNext(); /* no-op */)
 {
     // Return the first schema object found, which is the main schema
     //   loaded from the provided schemaURL
     Resource resource = (Resource)resources.next();
     if (resource instanceof XSDResourceImpl)
     {
         XSDResourceImpl xsdResource = (XSDResourceImpl)resource;
         // This returns a org.eclipse.xsd.XSDSchema object
         return xsdResource.getSchema();
     }
 }
 </code>
 </pre>
 </td>
 </tr>
 </tbody>
 </table>

 <p><a id="h3" name="h3"><span class="atitle2">Convenient schema
 querying</span></a><br />
 Now that you have an <code>XSDSchema</code> object, you need to
 query it to find any types that are missing max/min facets. First,
 you'll use some convenient library methods to quickly find all of
 its <code>simpleTypeDefinition</code>s that derive from the
 built-in integer type. Since the library provides a complete model
 of the abstract meaning of a schema, this turns out to be very
 straightforward. You can query the <code>XSDSchema</code> for its
 <code>getTypeDefinitions()</code> listing, and then filter for
 <code>XSDSimpleTypeDefinition</code>s that actually inherit from
 the base integer type.</p>

 <a id="code3" name="code3"><b>Listing 3. Getting a list of specific
 types</b></a>

 <table cellspacing="0" cellpadding="5" width="100%"
 bgcolor="#cccccc" border="1">
 <tbody>
 <tr>
 <td>
 <pre>
 <code>// A handy convenience method quickly gets all
 //   typeDefinitions within the schema
 List allTypes = schema.getTypeDefinitions();
 ArrayList allIntegerTypes = new ArrayList();

 for (Iterator iter = allTypes.iterator();
         iter.hasNext(); /* no-op */)
 {
     XSDTypeDefinition typedef = (XSDTypeDefinition)iter.next();
     // Filter out for only simpleTypes...
     if ((typedef instanceof XSDSimpleTypeDefinition)
         // ... and filter for built-in integer types
         // Use a worker method in the very handy sample
         //  program org.eclipse.xsd.util. XSDSchemaQueryTools
         &amp;&amp; XSDSchemaQueryTools.isTypeDerivedFrom(typedef,
                 schema.getSchemaForSchemaNamespace(), "integer"))
     {
         // The filter found one; save it and continue.
         allIntegerTypes.add(typedef);
     }
 }
 </code>
 </pre>
 </td>
 </tr>
 </tbody>
 </table>

 <p><a id="h4" name="h4"><span class="atitle2">The schema components
 model</span></a><br />
 Every component defined in the W3C schema specifications is modeled
 in detail in the library. Now that you have a list of all
 <code>XSDSimpleTypeDefinition</code>s that derive from an integer,
 you can query this list for ones that are missing either their max
 or min facets, and produce a report. Note that the library can
 conveniently group the effective max/minExclusive or
 max/minInclusive facets together for quick searching; it also
 provides detailed access to each type, including the actual lexical
 values if needed.</p>

 <a id="code4" name="code4"><b>Listing 4. Querying XSDSimpleType
 components</b></a>

 <table cellspacing="0" cellpadding="5" width="100%"
 bgcolor="#cccccc" border="1">
 <tbody>
 <tr>
 <td>
 <pre>
 <code>for (Iterator iter = allIntegerTypes.iterator();
         iter.hasNext(); /* no-op */)
 {
     XSDSimpleTypeDefinition simpleType = (XSDSimpleTypeDefinition)iter.next();
     // First, exclude any UNION or LIST types, since
     //  the schema spec says they can't have min/max facets:
     //  Part 2: Datatypes in:
     //  <a
 href="http://www.w3.org/TR/xmlschema-2/#defn-coss">'4.1.5 Constraints on Simple Type Definition Schema Components'</a>
     if ((XSDVariety.LIST_LITERAL == simpleType.getVariety())
         || (XSDVariety.UNION_LITERAL == simpleType.getVariety()))
     {
         // Unions and lists cannot have min/max facets at all,
         //  so there's no need to report them
         continue;
     }

     // Get the effective max/min facets for each type -
     //  this includes ones declared in this type or
     //  ones that are inherited, and so forth
     XSDMaxFacet maxFacet = simpleType.getEffectiveMaxFacet();
     XSDMinFacet minFacet = simpleType.getEffectiveMinFacet();

     // If you don't have the proper ones, report the error.
     if ((null == maxFacet) || (null == minFacet))
     {
         if (null != simpleType.getName())
         {
             // A component's URI in the library is effectively
             //  its &lt;target namespace&gt;#&lt;name&gt;
             System.out.println("Schema named component: " + simpleType.getURI() );
         }
         else
         {
             // It's an anonymous type, so ask the library
             //  to construct a default 'alias' for it
             System.out.println("Schema anonymous component: " + simpleType.getAliasURI() );
         }
         System.out.print(" is missing these required facets: ");
         if (null == maxFacet)
         {
             System.out.print(" XSDMaxFacet (either inclusive or exclusive) ");
         }
         if (null == minFacet)
         {
             System.out.print(" XSDMinFacet (either inclusive or exclusive) ");
         }
         // You could also report on the facets this type does have like:
         // if (minFacet.isExclusive) {
         // System.out.println("minFacet.getValue=" + minFacet.getValue());
         // }
     }
 }
 </code>
 </pre>
 </td>
 </tr>
 </tbody>
 </table>

 <p><a id="h5" name="h5"><span class="atitle2">Your report: Types
 missing max/min facets</span></a><br />
 With just a little bit of code, you've discovered some fairly
 detailed information about the schema. If you download the sample
 code and run it against the provided schema file, you should see a
 listing like this:</p>

 <a id="code5" name="code5"><b>Listing 5. The output report</b></a>

 <table cellspacing="0" cellpadding="5" width="100%"
 bgcolor="#cccccc" border="1">
 <tbody>
 <tr>
 <td>
 <pre>
 <code>Schema missing max/min facet report on: FindTypesMissingFacets.xsd
 Schema named component: http://www.research.ibm.com/XML/NS/xsd#integer-minFacet
   is missing these required facets:  XSDMaxFacet (either inclusive or exclusive)

 Schema named component: http://www.research.ibm.com/XML/NS/xsd#integer-noFacets
   is missing these required facets:  XSDMaxFacet (either inclusive or exclusive)
   XSDMinFacet (either inclusive or exclusive)

 Schema named component: http://www.research.ibm.com/XML/NS/xsd#positiveInteger-inheritedMinFacet
   is missing these required facets:  XSDMaxFacet (either inclusive or exclusive)
 </code>
 </pre>
 </td>
 </tr>
 </tbody>
 </table>

 <p><a id="conclusion" name="conclusion"><span
 class="atitle2">Conclusion</span></a><br />
 Although this is a contrived example, it does show how the
 library's detailed representation of a schema makes it easy to find
 exactly the parts of a schema you need. The library provides setter
 methods for the properties of schema components, so it is easy to
 update your sample to automatically fix any found types by adding
 any missing facets. And since the library models the concrete
 representation of the schema as well, you can write your updated
 schema back out to an <code>.xsd</code> file.</p>

 <p><a id="samplecode" name="samplecode"><span
 class="atitle2">Sample code</span></a><br />
 A sample program, <code>XSDFindTypesMissingFacets.java</code>,
 shows the example in this article. It uses a schema document
 <code>FindTypesMissingFacets.xsd</code> which has a number of types
 with and without max/min facets.</p>

 <p>You can download the sample program and the following sample
 .java files in a <a href="images/../dwtip1/xsdqcode.zip">zip
 file.</a></p>

 <p>Copies of several other sample .java files normally shipped with
 the Schema Infoset Model are also attached. These include:</p>

 <ul>
 <li><code>XSDSchemaQueryTools.java</code> showcases a number of
 other ways to perform advanced queries on schema objects.</li>

 <li><code>XSDSchemaBuildingTools.java</code> with convenience
 methods for building schemas programmatically.</li>

 <li><code>XSDPrototypicalSchema.java</code> uses the library to
 build the ever-popular schema <a
 href="http://www.w3.org/TR/xmlschema-0/#po.xsd">primer
 PurchaseOrder sample</a>.</li>
 </ul>

 <p><a id="resources" name="resources"><span
 class="atitle2">Resources</span></a></p>

 <ul>
 <li><a href="images/../dwtip1/xsdqcode.zip"><img
 src="images/../dwtip1/icon-zip.gif" alt="zip" border="0" /></a>
 Download a zip file with the <a
 href="images/../dwtip1/xsdqcode.zip">sample codes</a> for this
 article, including the sample program, schema document, and other
 .java files.<br />
 <br />
 </li>

 <li>See a full <a
 href="../../../references/articles/dwtip1-scpw/sidebar-listing.html">
 schema library class listing</a>.<br />
 <br />
 </li>

 <li>Read some of IBM's thoughts about <a
 href="http://www-106.ibm.com/developerworks/cgi-bin/click.cgi?url=http://www.research.ibm.com/XML/schema/WD-XML-Schema-Infoset-API-Req.htm&amp;origin=x">
 what makes a good schema API</a>.<br />
 <br />
 </li>

 <li>Start with an <a
 href="http://www.xml.com/pub/a/2000/11/29/schemas/part1.html">Introduction
 to XML Schemas</a> by Eric van der Vlist.<br />
 <br />
 </li>

 <li>See W3C's <a href="http://www.w3.org/XML/Schema">schema
 specifications</a> (primer, datatypes, and structures).<br />
 <br />
 </li>

 <li>Download Apache's <a
 href="http://xml.apache.org/xerces2-j/">Xerces-J parser</a>, which
 includes basic schema validation tools.<br />
 <br />
 </li>

 <li>View or discuss a previous version of this article <a
 href="http://www-106.ibm.com/developerworks/library/x-schemimj/index.html?loc=x">
 at IBM's developerWorks</a>.<br />
 <br />
 </li>
 </ul>

 <p>This content was adapted from an article on IBM developerWorks
 at <a
 href="http://www.ibm.com/developerWorks/">http://www.ibm.com/developerWorks/</a>.</p>

 <table cellspacing="0" cellpadding="0" width="100%" border="0">
 <tbody>
 <tr>
 <td><a id="author1" name="author1"><span class="atitle2">About the
 author</span></a><br />
 Shane Curcuru has been a developer and quality engineer at Lotus
 and IBM for 12 years and is a member of the Apache Software
 Foundation. He has worked on such diverse projects as Lotus 1-2-3,
 Lotus eSuite, Apache's Xalan-J XSLT processor, and a variety of XML
 Schema tools. Questions about this article or about automated
 testing can be sent to him at shane_curcuru@us.ibm.com.</td>
 </tr>
 </tbody>
 </table>

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 <img height="10" alt="" src="images/../dwtip1/c.gif" width="100"
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