MetaSchema

MetaSchema allows the definition of a schema to validate metadata.

Schema

The schema is defined using the EOL (Exteca Ontology Language) - see Exteca project for more details. An example schema looks like this: 

<ontology id="metadata-schema" uri="http://metadata/schema" version="1.0"> 
    <associations>
        <association id="has-metadata" inverse-id="metadata-of">
            <description>Association between artefact and metadata</description>
        </association>
    </associations>
    <attributes>
        <attribute id="param" data-type="String"/>
		<attribute id="avalon-service"  data-type="java.util.Properties"/>
    </attributes>
    <concepts>
        <concept id="java artefact">
            <has-subclass concept="class/interface"/>
            <has-subclass concept="method"/>
            <has-subclass concept="method parameter"/>
            <has-subclass concept="field"/>
            <has-subclass concept="package"/>
            <has-subclass concept="jar"/>
        </concept>
        <concept id="class/interface">
            <property attribute="param" value="param1 this is a parameter"/>
            <property attribute="avalon-service" value="type=Foo;context=Boo"/>
        </concept>
    </concepts>
    <contents>
        <concept-content concept="class/interface">
           <resources content="Resources">
                <resource name="assembly" uri="dtd:/org/apache/avalon/phoenix/tools/assembly.dtd"/>
                <resource name="banner" uri="pgn:/org/apache/avalon/phoenix/tools/phoenix.png"/>
                <resource name="kernel" uri="comp:/org.apache.avalon.phoenix.components.kernel.DefaultKernel"/>
            </resources>
        </concept-content>    
    </contents>
</ontology>
It allows to easily define a domain of knowledge, in this case a schema for validating artefacts and their attributes.

Attribute Validator

We have defined an attribute validator interface, which allows the validation of two types of attributes: by value and by Properties. 

public interface AttributeValidator {

	/**
	 *   Validates attribute of an artefact  
	 * 
	 *   @param artefactName the name of the artefact to which the attribute applies
	 *   @param name the name of the attribute
	 *   @param value the String representing the value of the attribute
	 */
	void validateAttribute(String artefactName, String name, String value)
		throws InvalidMetaDataException;

	/**
	 *   Validates attribute of an artefact
	 * 
	 *   @param artefactName the name of the artefact to which the attribute applies
	 *   @param name the name of the attribute
	 *   @param values the Properties representing the values of the attribute
	 */
	void validateAttribute(String artefactName, String name, Properties values)
		throws InvalidMetaDataException;

}