The xlink:arcrole attribute

• For situations where the nature/role alone isn't enough, this offers an additional URI defining the purpose of the link.

• Well-known purposes include:

  http://www.rddl.org/purposes#validation

  This resource should be used for classic XML or SGML DTD validation before the document is parsed.

  http://www.rddl.org/purposes#schema-validation

  This resource should be used for validation via some sort of schema after the document is parsed.; the The type of schema would normally be identified by the nature.

  http://www.rddl.org/purposes#module

  A file which that is only part of a complete DTD; and that is typically used in modularized DTDs like such as XHTML 1.1 and SMIL 2.0

  http://www.rddl.org/purposes#schema-module

  A module used in a schema

  http://www.rddl.org/purposes#entities

  A DTD fragment containing only entity definitions such as xhtml-special.ent in modular XHTML

  http://www.rddl.org/purposes#notations

  A DTD fragment containing only notation declarations such as xhtml-notations-1.mod in modular XHTML

  http://www.rddl.org/purposes/software#xslt-extension

  Software implementing an extension function or element for XSLT

  http://www.rddl.org/purposes/software#software-package

  A grouping of software resources

  http://www.rddl.org/purposes/software#software-project

  A collection of resources related to a software package

  http://www.rddl.org/purposes#JAR

  A zip file with the extension .jar containing Java classes

  http://www.rddl.org/purposes/software#reference

  Documentation for the resource

  http://www.rddl.org/purposes/software#normative-reference

  the definitive specification of the resource's syntax and semantics

  http://www.rddl.org/purposes/software#non-normative-reference

  A useful but non-authoritative description of the resource's syntax and semantics

  http://www.rddl.org/purposes#prior-version

  Documentation for a previous version of the resource's vocabulary; for example, the XHTML 1.0 specification relative to XHTML 1.1

  http://www.rddl.org/purposes#definition

  The definition of a term

  http://www.rddl.org/purposes#icon

  An image that represents the resource

  http://www.rddl.org/purposes#directory

  Another RDDL document whose resources should be merged with this document's resources

  http://www.rddl.org/purposes#alternate

  An alternative for a resource with the same nature as this one