The purpose of a resource link determines what the link will be used for.
Frequently the purpose of a link can be determined from the nature of the referenced resource.
For example the purpose of an XML Schema is typically schema validation, yet a schema may be comprised of
a number of included modules and even when included modules are themselves an XML Schema, the purpose is as a module.
This document defines a number of purposes for referenced resource links.
Validation is performed on XML or SGML documents using a DTD. The document type definition associates a document with a DTD to be used for validation.
Schema validation is distinct from DTD validation because schema validation is performed after the parse phase whereas DTD validation may be combined with the parse phase. The term post schema-validation infoset refers to the document infoset which results after a schema validation, whereas the pre schema-validation infoset is the infoset which is present after the document is parsed.
A module may be included as part of a schema or software program.
A schema module is a module which is used particularly within a schema.
It is frequently convenient to package a set of entity definitions in an external module.
It is frequently convenient to package a set of notation definitions in an external module.
A software module is a module which is used particularly within a software program.
A software package is a grouping of software resources.
A software project is a collection of resources related to a software package. A project is usually identified by a home page URI.
A java archive is a module packaged using the application/pkzip format whose purpose is to be used as a package of java classes, code and/or associated resources.
A reference is often an associated piece of documentation. Referenced may be subclassified into
normative-references and non-normative-referenced among others.
A normative reference is a document whose definitions are normative to the referencing document.
A non normative reference is a document whose definitions are not normative to the referencing document.
One type of purpose is a definition of a term.
A resource link may define a term in which case the nature of the referenced
resource is a term i.e. http://www.rddl.org/natures#term and the purpose
is a definition i.e. http://www.rddl.org/purposes#definition.
An icon to be associated with a project has the purpose http://www.rddl.org/purposes#icon. Its nature
might be either image/gif or image/jpeg.
An alternate.
A resource documenting or implementing an application specific canonicalization algorithm. This feature is most usefull for applications allowing different syntaxes to express the same data model and provides then a way to define which syntax is "canonical" and may be used for document comparison, signature or validation.
The purpose http://www.rddl.org/purposes#target is used to indicate an intended target URI of the RDDL directory.