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// Copyright (c) 2020 Contributors to the Eclipse Foundation
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== [[a151]]Requirements

This chapter specifies the scope and requirements for this version of the specification.

=== XML Schema to Java

==== W3C XML Schema support

The mapping of the following XML Schema
components must be specified.

* type substitution ( _@xsi:type_ )
* element substitution group ( _<xs:element
@substitutionGroup_ >)
* wildcard support( _xs:any_ and
_xs:anyAttribute_ )
* identity constraints ( _xs:key_ ,
_xs:keyref_ and _xs:unique_ )
* redefinition of declaration ( _xs:redefine_
)
* NOTATION

For binding builtin XML Schema datatypes which
do not map naturally to Java datatypes, Java datatypes specified by JAXP
1.3 (JSR 206) must be used.

==== Default Bindings

There must be a detailed, unambiguous
description of the default mapping of schema components to Java
representations in order to satisfy the portability goal.

==== Customized Binding Schema

A binding schema language and its formats must
be specified. There must be a means to describe the binding without
requiring modification to the original schema. Additionally, the same
XML Schema language must be used for the two different mechanisms for
expressing a binding declaration.

==== Overriding default binding behavior

Given the diverse styles that can be used to
design a schema, it is daunting to identify a single ideal default
binding solution. For situations where several equally good binding
alternatives exist, the specification will describe the alternatives and
select one to be the default (see link:jaxb.html#a165[See
Customized Binding Schema]).

The binding schema must provide a means to
specify an alternative binding for the scope of an entire schema. This
mechanism ensures that if the default binding is not sufficient, it can
easily be overridden in a portable manner.

==== Jakarta XML Web Services

===== Backward Compatibility

Mapping of XML Schema to schema derived Java
classes as specified in versions of Jakarta XML-RPC either by default or by
customization is out of scope.

===== Binding XML Schema to schema derived classes

A binding of XML Schema constructs to schema
derived classes must be specified.

===== Accessing MIME content stored as an attachment

The W3C XMLP MTOM/XOP document and WS-I AP
1.0[WSIAP] both provide mechanisms for embedding references to SOAP
attachments in SOAP messages. It is desirable to bind these to suitable
Java types (e.g. Image or DataHandler) rather than just provide URI
refs.

===== Serializable

A customization must be specified to enable
schema derived classes to implement the `java.io.Serializable`
interface. This capability enables the schema derived instance to be
passed as EJB method parameter and to any other API that requires
Serializable instances.

===== Disabling Databinding

A customization to disable databinding must be
specified. When databinding is disabled, an XML Schema component is
bound to an XML fragment representation rather than a strongly typed
datatype determined by mapping rules. Binding to XML fragment allows the
use of alternative binding technologies for example to perform XML
operations.

=== Java to XML Schema

==== Default Mapping

A default mapping Java constructs to XML
Schema must be specified. The default mapping may be overridden by
customizations described in link:jaxb.html#a184[See Customized
Mapping]”.

==== Customized Mapping

A customization mechanism to override default
mapping of Java constructs to XML Schema constructs must be specified.
Since XML Schema provides a much richer feature set than Java language
for defining data models, the scope of customizations will be restricted
to enable mapping to commonly used XML Schema constructs.

Support for the following mechanism must be
specified:

* customization mechanism using the JSR175
program annotation facility.

==== Jakarta XML Web Services

===== WSDL <types>

The WSDL <types> is generated using Java
constructs to XML Schema mapping. The latter should therefore define
customizations that enable mapping to XML Schema constructs commonly
used in web services, subject to the requirements in
link:jaxb.html#a184[See Customized Mapping]” and
link:jaxb.html#a182[See Default Mapping]”.

===== Backward Compatibility

Mapping of existing Java constructs to XML
Schema constructs as specified in Jakarta XML-RPC, either by
default or through customization, is out of scope.

=== Binding Framework

==== Disabling schema validation

The specification will provide an ability to
disable schema validation for unmarshal and marshal operations.

There exist a significant number of scenarios
that do not require validation and/or can not afford the overhead of
schema validation. An application must be allowed to disable schema
validation checking during unmarshal and marshal operations. The goal of
this requirement is to provide the same flexibility and functionality
that a SAX or DOM parser allows for.