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<?xml version='1.0' encoding='UTF-8'?>
<!--
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
-->
<!DOCTYPE s1 SYSTEM 'dtd/document.dtd'>
<s1 title="XML Schema">
<s2 title="Introduction">
<p>This package contains the implementations of the W3C XML
Schema 1.0 and 1.1 Languages, that are recommendation of the Worldwide Web Consortium.
The XML Schema 1.0 Language is available in three parts:
<jump href="http://www.w3.org/TR/XMLSchema-0">XML Schema: Primer</jump> and
<jump href="http://www.w3.org/TR/XMLSchema-1">XML Schema: Structures</jump> and
<jump href="http://www.w3.org/TR/XMLSchema-2">XML Schema: Datatypes</jump>.
The XML Schema 1.1 Language is available in two parts:
<jump href='http://www.w3.org/TR/xmlschema11-1/'>Structures</jump> and
<jump href='http://www.w3.org/TR/xmlschema11-2/'>Datatypes</jump>.
The XML Schema 1.1 features supported by this release are listed below.
In this document we also discuss our interpretation of the
specifications where it seems to us particularly likely that
others might arrive at a different interpretation.
We consider this implementation to be complete except for the
limitations cited below. The implementation has been
extensively tested and known problem areas are set out below.
Please read this document before using this package.
</p>
</s2>
<s2 title="XML Schema Programmer's Guide">
<p>This section provides the following topics:</p>
<ul>
<li><jump href='#supported-schema-1.1-features'>Supported XML Schema 1.1 Features</jump></li>
<li><jump href='#schema-limitations'>Limitations and known bugs</jump></li>
<li><link idref='faq-xs'>How do I?</link> --
the most frequently asked questions
about XML Schema that include some sample code.</li>
</ul>
</s2>
<anchor name="supported-schema-1.1-features"/>
<s2 title="Supported XML Schema 1.1 Features">
<ul>
<li>All Groups</li>
<ul>
<li>maxOccurs may now be >1</li>
<li>Wildcards are now allowed</li>
<li>Derivation by extension</li>
<li>xs:group is allowed as a child of xs:all</li>
</ul>
<li>Assertions</li>
<li>Conditional Type Assignment</li>
<li>Simplified Complex Type restriction rules (also known as Subsumption)</li>
<li>Open Content and Default Open Content</li>
<li>Default attribute group</li>
<li>Target namespace on local element/attribute declarations</li>
<li>Element declarations allowed in more than one substitution group</li>
<li>Wildcards</li>
<ul>
<li>not namespace</li>
<li>not QName</li>
<li>not #defined</li>
<li>not #definedSibling</li>
<li>Relaxation of UPA in the presence of wildcards</li>
</ul>
<li>Overriding component definitions (xs:override)</li>
<li>Conditional Inclusion</li>
<ul>
<li>vc:minVersion</li>
<li>vc:maxVersion</li>
<li>vc:typeAvailable</li>
<li>vc:typeUnavailable</li>
<li>vc:facetAvailable</li>
<li>vc:facetUnavailable</li>
</ul>
<li>Context property for local simple/complex type definitions</li>
<li>explicitTimezone facet and dateTimeStamp derived type</li>
<li>yearMonthDuration and dayTimeDuration derived types</li>
<li>precisionDecimal type</li>
<li>Union types not expanded</li>
<li>ID/IDREF</li>
<ul>
<li>Lists of ID</li>
<li>Unions involving ID</li>
<li>Multiple attributes of type ID</li>
<li>Default values of type IDREF</li>
<li>Default values for elements or attributes of type ID</li>
</ul>
</ul>
</s2>
<anchor name='schema-limitations'/>
<s2 title="Limitations">
<ul>
<li> Length, minLength, and maxLength facets are limited to the value
2147483647. Items larger than this limit will not be validated
correctly.</li>
<li> The values of minOccurs and maxOccurs attributes are limited to
the value 2147483647. Items larger than this limit will not be
validated correctly.</li>
<li> The values of minimum and maximum quantifiers in the pattern
regular expressions are limited to the value 2147483647.
Items larger than this limit will not be validated correctly.</li>
<li> The absolute values of the fraction portion of the second values
in date/time datatypes are limited to the value 2147483647.
Items larger than this limit will not be validated correctly.
i.e. 11.2147483648 is not supported as a second value. </li>
<li> Leap seconds are not supported in the values of date/time datatypes.</li>
</ul>
</s2>
<s2 title='Problem Areas/Known Bugs'>
<ul>
<li> For larger values of maxOccurs, an OutOfMemoryError may occur.
The workaround for this problem, if your application permits it,
is to change the maxOccurs value to unbounded. If you are unable to
change the schema you can configure Xerces-J so that it fails more
gracefully by enabling the JAXP secure processing feature. See the
Javadoc for javax.xml.XMLConstants.FEATURE_SECURE_PROCESSING for
more details.
</li>
<li> The JAXP class javax.xml.validation.Schema is defined to be thread
safe. That is, applications are encouraged to share javax.xml.validation.Schema objects
across multiple threads. Some Xerces users have reported that, while doing XML Schema 1.1
validation javax.xml.validation.Schema is seen to be not thread safe. This problem was
observed in certain use cases, while using the XSD 1.1 construct <assert> in the
XSD documents. But there are also, various cases observed while using XSD 1.1
construct <assert>, when thread safety of javax.xml.validation.Schema is
seen to be working correctly.
</li>
</ul>
</s2>
<s2 title="Other Notes">
<ul>
<li> As of version 2.2.1, it is hoped that Xerces-J will always
be able to parse the Schema for Schemas current at the time of the product's release. As of version
2.2.1, this implies inserting special logic to permit the presence of
the built-in Schema datatypes in this particular schema; an
issue has been raised with the Schema Working Group, in hopes the document
will be modified so that the built-in types are no
longer presented as global components. Thus, anyone planning
to rely on the Schema for Schemas should be aware that the
possibility exists that a change of this sort might be made in the future.</li>
<li> In the original XML Schema recommendation, the lexical space of
the simple type <code>gMonth</code> is <code>--MM--</code>. An erratum E2-12
changed that to <code>--MM</code>. For compatibility reasons, Xerces currently
supports both forms. To align with the recommendation, we have decided to
deprecate the old form, and plan to discontinue support for that form
in a future release. </li>
</ul>
</s2>
</s1>
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