XML Schema


	Introduction

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: XML Schema: Primer and XML Schema: Structures and XML Schema: Datatypes. The XML Schema 1.1 Language is available in two parts: Structures and Datatypes. In this document we 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 within this document. The implementation has been extensively tested and known problem areas are set out within this document. Please read this document before using this package.


	Xerces-J's compliance to W3C XML Schema test suite

Following are Xerces-J's compliance reports for the W3C XML Schema test suite:


	XML Schema Programmer's Guide

This section provides the following topics:

Supported XML Schema 1.1 Features
Limitations and known bugs
How do I? -- the most frequently asked questions about XML Schema that include some sample code.


	Supported XML Schema 1.1 Features

All Groups

maxOccurs may now be >1
Wildcards are now allowed
Derivation by extension
xs:group is allowed as a child of xs:all

Assertions
Conditional Type Assignment
Simplified Complex Type restriction rules (also known as Subsumption)
Open Content and Default Open Content
Default attribute group
Target namespace on local element/attribute declarations
Element declarations allowed in more than one substitution group
Wildcards

not namespace
not QName
not #defined
not #definedSibling
Relaxation of UPA in the presence of wildcards

Overriding component definitions (xs:override)
Conditional Inclusion

vc:minVersion
vc:maxVersion
vc:typeAvailable
vc:typeUnavailable
vc:facetAvailable
vc:facetUnavailable

Context property for local simple/complex type definitions
explicitTimezone facet and dateTimeStamp derived type
yearMonthDuration and dayTimeDuration derived types
precisionDecimal type
Union types not expanded
ID/IDREF

Lists of ID
Unions involving ID
Multiple attributes of type ID
Default values of type IDREF
Default values for elements or attributes of type ID


	Limitations

Length, minLength, and maxLength facets are limited to the value 2147483647. Items larger than this limit will not be validated correctly.
The values of minOccurs and maxOccurs attributes are limited to the value 2147483647. Items larger than this limit will not be validated correctly.
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.
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.
Leap seconds are not supported in the values of date/time datatypes.


	Problem Areas/Known Bugs

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.


	Other Notes

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.
In the original XML Schema recommendation, the lexical space of the simple type gMonth is --MM--. An erratum E2-12 changed that to --MM. 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.