Protocol for Web Description Resources (POWDER): POWDER-S Vocabulary (WDRS)

1 Introduction

The Protocol for Web Description Resources (POWDER) allows metadata to be associated with groups of resources such as those found on a Web site. Its main 'unit of information' is the Description Resource (DR), one or more of which are contained in a POWDER document. Processing such a document yields RDF triples describing the resources that are within the scope of the DRs. POWDER documents are written in XML and have relatively loose semantics, however, a GRDDL transform, associated with the root namespace, renders the data in RDF/OWL with more formal semantics.

An RDF vocabulary is defined to support Semantic POWDER, or POWDER-S encoding, of Description Resources. This is the namespace document for that vocabulary. Although this document sets out the domain and range of each term, their full definitions are to be found in other documents in the set, notably the Description Resources document [DR] and the Formal Semantics document [FORMAL].

1.1 Namespaces

The POWDER-S vocabulary namespace is http://www.w3.org/2007/05/powder-s# for which we use the prefix wdrs. All prefixes used in this document, together with their associated namespaces, are shown in the table below.

Prefix	Namespace
wdrs	http://www.w3.org/2007/05/powder-s#
rdf	http://www.w3.org/1999/02/22-rdf-syntax-ns#
rdfs	http://www.w3.org/2000/01/rdf-schema#
owl	http://www.w3.org/2002/07/owl#
dcterms	http://purl.org/dc/terms/
xsd	http://www.w3.org/TR/xmlschema-2/

2 The Vocabulary Terms

2.1 Classes

2.1.1 Class Document

A POWDER document.

2.1.2 Class Processor

A software agent able to process POWDER documents.

2.2 Properties

2.2.1 Property text

This property provides a summary of the descriptorset that it annotates, suitable for display to end users.

2.2.2 Property issuedby

This property denotes the author of a POWDER document.

2.2.3 Property matchesregex

This is the key 'include' property for IRI set definitions in POWDER-S. It is necessary to take account of the POWDER Semantic Extension to process this fully. The value is a regular expression that is matched against an IRI.

2.2.4 Property notmatchesregex

This is the key 'exclude' property for IRI set definitions in POWDER-S. It is necessary to take account of the POWDER Semantic Extension to process this fully. The value is a regular expression that is matched against an IRI.

2.2.5 Property hasIRI

This property is meant to be used in OWL2 instead of wdrs:matchesregex. It denotes the string data range corresponding to a set of IRIs.

2.2.6 Property tag

Property linking to a free-text tag which may include spaces.

2.2.7 Property notknownto

Property used in results returned from a POWDER Processor that has no data about the candidate resource. The value is the IRI of the processor.

2.2.8 Property describedby

An RDF property to exactly match the describedby relationship type introduced in http://www.w3.org/TR/powder-dr/#assoc-linking and formally defined in appendix D of the same document, i.e. the relationship A 'describedby' B asserts that resource B provides a description of resource A. There are no constraints on the format or representation of either A or B, neither are there any further constraints on either resource.

2.2.9 Property authenticate

A pointer to a document that describes how Description Resources created by a FOAF Agent or a DC Terms Agent may be authenticated

2.2.10 Property validfrom

Provides a timestamp that a POWDER Processor may use when assessing trustworthiness of a POWDER document. Informally, a POWDER Processor should normally ignore data in the document before the given date.

2.2.11 Property validuntil

Provides a timestamp that a POWDER Processor may use when assessing trustworthiness of a POWDER document. Informally, a POWDER Processor should normally ignore data in the document after the given date.

2.2.12 Property logo

Points to a graphic summary for the resources in a given class. Typically, it is a logo denoting conformance of a given (set of) resource(s) to a given set of criteria.

2.2.13 Property sha1sum

Links to a Base64-encoded binary SHA-1 hash of the described resource. May be used by POWDER Processors when assessing trustworthiness of a DR.

2.2.14 Property certified

A property that takes a Boolean value to declare whether the author of the data certifies the described resource.

2.2.15 Property certifiedby

A property that links a resource to a POWDER document that certifies it.

2.2.16 Property supportedby

A property that links a POWDER document to some other data source that supports the descriptions provided.

2.2.17 Property data_error

A property denoting a description of the specific error found in a given POWDER document.

2.2.18 Property proc_error

A property denoting a description of the specific software error.

2.2.19 Property error_code

A property denoting the code of any error encountered by the POWDER processor.

References

[FORMAL]

Protocol for Web Description Resources (POWDER): Formal Semantics, S. Konstantopoulos, P. Archer. This document is at http://www.w3.org/TR/powder-formal/

[DR]

Protocol for Web Description Resources (POWDER): Description Resources, P Archer, K. Smith, A Perego. This document is at http://www.w3.org/TR/powder-dr/

Acknowledgements

The editors duly acknowledge contributions made by all members of the POWDER Working Group.