# EMF Validation Constraint Bindings

###### Identifier:

org.eclipse.emf.validation.constraintBindings

###### Since:

1.0

###### Description:

This extension point allows clients of the EMF Validation framework to define "client contexts" that describe the objects that they are interested in validating, and to bind them to constraints that they are interested in enforcing on these objects.

###### Configuration Markup:

<!ELEMENT extension (clientContext* , binding*)>

<!ATTLIST extension

point CDATA #REQUIRED

id CDATA #IMPLIED

name CDATA #IMPLIED

>

<!ELEMENT clientContext (enablement | selector)>

<!ATTLIST clientContext

id CDATA #REQUIRED

default (true | false)

>

Definition of a client context, representing a class of objects that a client wishes to apply a set of constraints to.

A client context can declare an `<enablement>` expression that matches model elements that are included in the context. Where that is not sufficient, an alternative is to define a selector class using a `<selector>` element.

- id - The unique ID of the client context.
- default - Optionally indicates that the client context is to be considered as a "default" context. A default context is implicitly bound to every constraint for which there is no other context explicitly bound to it. By default, a client context is not default.

<!ELEMENT selector EMPTY>

<!ATTLIST selector

class CDATA #REQUIRED

>

A selector determines which model elements are included in a client context when an XML expression is too cumbersome or somehow not sufficient to implement the test.

- class - Identifies a class implementing the `org.eclipse.emf.validation.internal.model.IClientSelector` internal API interface.

<!ELEMENT binding ((category | constraint | extendClientContext | excludeCategory | excludeConstraint)*)>

<!ATTLIST binding

context CDATA #REQUIRED

constraint CDATA #IMPLIED

category CDATA #IMPLIED

>

Declares a binding between a client context and one or more constraints. The context can, itself, be declared by the same plug-in or by a different plug-in.

The constraints to be bound may be specified by either:

- the `constraint` attribute, to reference a single constraint
- the `category` attribute, to reference a single constraint category and all of the constraints that it includes
- any number of nested `<constraint>` and/or `<category>` elements to reference multiple constraints and/or categories

Since the 1.3 release, selective exclusion of constraints and sub-categories that are contained by included categories is supported. Within a `<binding>` element, ordering of inclusion and exclusion elements is significant: they are processed in the order in which they are declared in the extension. However, the order of inclusions and exclusions in separate bindings for the same context is undefined.

- context - References the ID of a context that is bound to one or more constraints.
- constraint - Identifies a single constraint to be bound to the client context. This attribute may not be used in conjunection with the `category` attribute.
- category -

  Identifies a constraint category to be bound to the client context. The referenced category and all of its constraints, sub-categories, and their constraints are bound.

  This attribute may not be used in conjunection with the `constraint` attribute.

<!ELEMENT constraint EMPTY>

<!ATTLIST constraint

ref CDATA #REQUIRED

>

Includes a constraint in a client context `<binding>`.

- ref - References the fully-qualified ID of a constraint to bind the client context to. The ID includes the constraint's contributing plug-in ID, if it is not explicit in the XML definition of the constraint.

<!ELEMENT category EMPTY>

<!ATTLIST category

ref CDATA #REQUIRED

>

Includes a constraint category in a client context `<binding>`. All of the referenced category's constraints and those of any sub-categories (recursively) are included.

- ref - References the fully-qualified ID of a constraint category to bind the client context to. The category ID does not necessarily include its contributing plug-in ID, but is a path reflecting the hierarchical structure of categories.

<!ELEMENT extendClientContext EMPTY>

<!ATTLIST extendClientContext

ref CDATA #REQUIRED

>

Since 1.3. References a client-context that the bound context extends. Conceptually, this declares that objects matching the referenced context also match my bound context. In practice, this means that my bound context inherits all of the constraint bindings from the referenced context.
Of course, subsequent exclusions can filter out unwanted constraints, too. Note, also, that this effects a dependency on the referenced client context and also imposes a partial ordering on the bindings. All of the bindings contributed to the referenced context are applied before any inclusions or exclusions that follow the `<extendClientContext>` element in the current `<binding>`.

- ref - References the ID of a client-context to extend. All constraint bindings of the client context are inherited by this binding.

<!ELEMENT excludeCategory EMPTY>

<!ATTLIST excludeCategory

ref CDATA #REQUIRED

>

Since 1.3. Excludes a constraint category from a client context `<binding>`. All of the referenced category's constraints and those of any sub-categories (recursively) are excluded. This is useful when including some parent category, to filter out selective sub-categories. Not only is it simpler than explicitly including all of the desired sub-categories, but it ensures that sub-categories that are added later will be included implicitly.

- ref - References the fully-qualified ID of a constraint category to exclude from the client context. The category ID does not necessarily include its contributing plug-in ID, but is a path reflecting the hierarchical structure of categories.

<!ELEMENT excludeConstraint EMPTY>

<!ATTLIST excludeConstraint

ref CDATA #REQUIRED

>

Since 1.3. Excludes a constraint from a client context `<binding>`. This is useful when including some parent category, to filter out selective constraints cointained within it. Not only is it simpler than explicitly including all of the desired constraints and sub-categories, but it ensures that constraints and sub-categories that are added later will be included implicitly.

- ref - References the fully-qualified ID of a constraint to exclude from the client context. The ID includes the constraint's contributing plug-in ID, if it is not explicit in the XML definition of the constraint.

###### Examples:

Example of a context which includes `EObjects` in *.library resources only, not in some other kind of resource that uses the EMF Library example meta-model (utilizing an hypothetical property tester):

       <extension point="org.eclipse.emf.validation.constraintBindings">
          <clientContext id="com.example.MyClient">
             <enablement>
                <with variable="resource"/>
                   <test
                      property="com.example.matchURI"
                      value="*.library"/>
                </with>
             </enablement>
          </clientContext>
       </extension>

Example of a binding of a single constraint to the MyClient context:

       <extension point="org.eclipse.emf.validation.constraintBindings">
          <binding
             context="com.example.MyClient"
             constraint="org.eclipse.uml2.validation.classifiers.genCycle"/>
       </extension>

Example of binding multiple constraints and constraint categories to the MyClient context:

       <extension point="org.eclipse.emf.validation.constraintBindings">
          <binding context="com.example.MyClient"/>
             <constraint ref="org.eclipse.uml2.validation.namespace.distinctMembers"/>
             <constraint ref="org.eclipse.uml2.validation.classifiers.genCycle"/>
             <category ref="uml2/spec/classes/kernel/namespaces"/>
             <category ref="uml2/spec/classes/kernel/classifiers"/>
          </binding>
       </extension>

Copyright (c) 2005, 2008 IBM Corporation, Zeligsoft Inc., and others.
All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License v1.0 which accompanies this distribution, and is available at http://www.eclipse.org/legal/epl-v10.html