Identity Schema Element Metadata: Using Existing Specifications

Abstract

This document specifies how existing RDF predicate definitions can be used for describing schema elements such as claim types and attribute types in an identity metasystem.

Table of Contents

1.  Introduction
2.  Recommended predicates
    2.1.  Predicates for describing attribute and claim types
    2.2.  Predicates for describing schemas
3.  Guidance on use of other specifications
4.  Examples
    4.1.  RDFa
5.  Security Considerations
6.  IANA Considerations
7.  References
    7.1.  Normative References
    7.2.  Informative References
Appendix A.  Copyright
§  Author's Address

1.  Introduction

This document specifies how RDF (Klyne, G. and J. Carroll, “Resource Description Framework (RDF): Concepts and Abstract Syntax,” February 2004.) [RDF.Concepts] predicates in existing ontologies can be used in metadata describing schema elements. This document is to be read in combination with the document Identity Schema Element Metadata: New Specifications (Wahl, M., “Identity Schema Element Metadata: New Specifications,” September 2007.) [Schema.New].

The following namespace prefixes are used in this document:

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#

dc: http://purl.org/dc/elements/1.1/

higgins: http://www.eclipse.org/higgins/ontologies/2006/higgins.owl#

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].

Please send comments to the identity schemas WG mailing list at idschemas@idcommons.net.

2.  Recommended predicates

This section lists the predicates which are defined in existing ontologies and RECOMMENDED to be used for describing schema elements and schemas.

2.1.  Predicates for describing attribute and claim types

An application which generates an RDF description of an attribute type or claim type SHOULD use the following predicates in triples describing that schema element.

• One or more triples with predicate rdfs:label SHOULD be generated, each with a value that contains a human-readable short text label for the attribute type or claim type. Each label SHOULD be limited to approximately 80 characters.
• One or more triples with predicate rdfs:comment SHOULD be generated, each with a value that contains a human-readable text description for the attribute type or claim type. Each comment SHOULD be limited to 65536 characters.
• If this attribute type or claim type is similar to another attribute type or claim type (but not identical), then one or more triples with predicate rdfs:seeAlso SHOULD be generated, each with a value that is a URI of the definition of the atribute type or claim type that is similar to this one.

An application which generates an RDF description of an attribute type or claim type for which there is no existing RDF definition MAY use the following predicates in triples describing that schema element. The choice of predicates is determined by the schema designer, who determines whether the attribute type or claim type is to be modeled as an OWL datatype property, an OWL object property, or an OWL class.

If the schema designer has decided the attribute type or claim type is to be modeled as an OWL datatype property, then

• One triple with predicate rdf:type SHOULD be generated, with the object URI "http://www.w3.org/2002/07/owl#DatatypeProperty".
• If this attribute type or claim type is identical to another attribute type or claim type that has been defined with a different URI, then one triple with predicate owl:equivalentProperty SHOULD be generated, with the object of the triple the URI of that other definition.

If the schema designer has decided the attribute type or claim type is to be modeled as an OWL object property, then

• One triple with predicate rdf:type SHOULD be generated, with the object URI "http://www.w3.org/2002/07/owl#ObjectProperty".
• One triple with predicate rdfs:subPropertyOf SHOULD be generated, with the object URI "http://www.eclipse.org/higgins/ontologies/2006/higgins.owl#attribute".
• If this attribute type or claim type has been determined to be identical to another attribute type or claim type that has been defined with a different URI, then one triple with predicate owl:equivalentProperty SHOULD be generated, with the object of the triple the URI of that other definition.

If schema designer has decided that the attribute type or claim type is to be modeled as an OWL class, then

• One triple with predicate rdf:type SHOULD be generated, with the object URI "http://www.w3.org/2002/07/owl#Class".
• One triple with predicate rdfs:subClassOf SHOULD be generated, with the object URI "http://www.eclipse.org/higgins/ontologies/2006/higgins.owl#Attribute".
• If this attribute type or claim type has been determined to be identical to another attribute type or claim type that has been defined with a different URI, then one triple with predicate owl:equivalentClass SHOULD be generated, with the object of the triple the URI of that other definition.

Triples with other predicates MAY be present in the description. In particular, see Identity Schema Element Metadata: New Specification (Wahl, M., “Identity Schema Element Metadata: New Specifications,” September 2007.) [Schema.New] for a list of additional predicates that are useful for describing attribute types and claim types.

As there is currently no industry consensus on whether an attribute type is to be modeled as an OWL datatype property, as an OWL object property, as an OWL class, or as none of these, an application which receives an RDF description of an attribute type or claim type is to be 'liberal in what it accepts' and MUST NOT require that a triple with predicate rdf:type, rdfs:subClassOf or rdfs:subPropertyOf be provided. If triples with those predicates are provided to an application, the application that receives them MUST allow the triples to have as their object any valid URI, except as noted in section 3 below.

2.2.  Predicates for describing schemas

An application which generates an RDF description of a schema (a collection of attribute type or claim type definitions) SHOULD use the following predicates in triples describing that schema.

• One or more triples with predicate rdfs:label SHOULD be generated, each with a value that contains a human-readable short text label for the schema. Each label SHOULD be limited to approximately 80 characters.
• One or more triples with predicate rdfs:comment SHOULD be generated, each with a value that contains a human-readable text description for the schema. Each comment SHOULD be limited to 65536 characters.
• The Dublin Core Metadata Element Set (, “Dublin Core Metadata Element Set, Version 1.1,” December 2006.) [DC.es] contains 15 properties that have been standardized by ISO for resource description. One or more triples with the predicates dc:contributor, dc:coverage, dc:creator, dc:date, dc:description, dc:format, dc:identifier, dc:language, dc:publisher, dc:relation, dc:rights, dc:source, dc:subject, dc:title, dc:type SHOULD be generated when there are appropriate values for those predicates available to describe the schema. As specified in Expressing Simple Dublin Core in RDF/XML (Beckett, D., Miller, E., and D. Brickley, “Expressing Simple Dublin Core in RDF/XML,” July 2002.) [DC.xml], "if the value of the Dublin Core element is a resource which has a URI rather than plain text, it should be recorded in the value of the rdf:resource attribute on the tag, with empty tag content".
• One triple with predicate rdf:type SHOULD be generated, with the object URI "http://www.w3.org/2002/07/owl#Ontology".
• One triple with predicate owl:versionInfo SHOULD be generated, with a value that contains a human-readable text string encoding a version number or date of the schema. This value SHOULD be limited to approximately 80 characters, and is typically a string generated by a revision control system such as CVS.
• One triple with predicate owl:imports SHOULD be generated, with the object URI "http://www.eclipse.org/higgins/ontologies/2006/higgins.owl".
• If the schema being described has dependencies on other schemas, then one or more triples with predicate owl:imports SHOULD be generated, in which the object URI of a triple is the URI of another schema on which this schema is dependent.

The properties listed in the DCMI Metadata terms (, “DCMI Metadata Terms,” December 2006.) [DC.terms] document, abstract, accessRights, accuralMethod, accrualPeriodicity, accrualPolicy, alternative, audience, available, bibliographicCitation, conformsTo, created, dateAccepted, dateCopyrighted, dateSubmitted, educationLevel, extent, hasFormat, hasPart, hasVersion, instructionalMethod, isFormatOf, isPartOf, isReferencedBy, isReplacedBy, isRequiredBy, issued, isVersionOf, license, mediator, medium, modified, provenance, references, replaces, requires, rightsHolder, spatial, tableOfContents, temporal and valid, MAY be used to provide additional description of a schema.

Triples with other predicates MAY be present in the description.

As there is currently no industry consensus on whether an identity schema is to be modeled as an OWL ontology, an application which receives an RDF description of a schema MUST NOT require that a triple with predicate rdf:type be provided. If triples with this predicates is provided to an application, the application that receives them MUST allow the triples to have as their object any valid URI, except as noted in section 3 below.

3.  Guidance on use of other specifications

• The XML attribute xml:lang SHOULD NOT be used on rdf:Description nodes representing schema elements. It MAY be used on individual triples, e.g. for setting a language of a particular rdfs:label.
• The rdf:type predicate MAY be used to describe a schema element. However, the values rdf:Seq, rdf:Bag, rdf:Alt, rdf:List SHOULD NOT be used as the object of this predicate when describing an attribute type or claim type.

ISSUE: this document does not currently specify how rdfs:subClassOf, rdfs:subPropertyOf, rdfs:range and rdfs:domain are to be used.

ISSUE: should owl:DeprecatedClass and owl:DeprecatedProperty be mentioned?

4.  Examples

4.1.  RDFa

An RDFa representation in a file with Content-Type application/xhtml+xml. This example only uses predicate definitions from existing specifications.

<?xml version="1.0"?>
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
      xmlns:dc="http://purl.org/dc/elements/1.1/"
      xmlns:owl="http://www.w3.org/2002/07/owl#"
      xmlns:higgins="http://www.eclipse.org/higgins/ontologies/2006/higgins.owl#">
<head about="">
 <title property="rdfs:label">Example schema containing two attribute types.</title>
 <meta property="rdfs:comment" xml:lang="en" content="This schema has two attribute type definitions: patronymic and age." />
 <meta property="owl:versionInfo" xml:lang="en" content="$1.1$" />
 <link rel="rdf:type" href="http://www.w3.org/2002/07/owl#Ontology" />
 <link rel="owl:imports" href="http://www.eclipse.org/higgins/ontologies/2006/higgins.owl" />
</head>
<body>
 <ul about="#patronymic">
  <li><span property="rdfs:label">Patryonymic</span></li>
  <li>This is an <a rel="rdf:type" href="http://www.w3.org/2002/07/owl#ObjectProperty">OWL ObjectProperty</a>.</li>
  <li>This is a sub-property of a
   <a rel="rdfs:subPropertyOf" href="http://www.eclipse.org/higgins/ontologies/2006/higgins.owl#attribute">Higgins attribute</a>.</li>
  </ul>

 <ul about="#age">
  <li><span property="rdfs:label">Age</span></li>
  <li><span property="rdfs:label" lang="de">Alter</span> (German)</li>
  <li><span property="rdfs:label" lang="fr">&#xC2;ge</span> (French)</li>
  <li>Comment: <span property="rdfs:comment">How old a person is (in years)</span></li>
  <li>This is an <a rel="rdf:type" href="http://www.w3.org/2002/07/owl#ObjectProperty">OWL ObjectProperty</a>.</li>
  <li>This is a sub-property of a
   <a rel="rdfs:subPropertyOf" href="http://www.eclipse.org/higgins/ontologies/2006/higgins.owl#attribute">Higgins attribute</a>.</li>
  </ul>
</body>
</html>

5.  Security Considerations

Security issues are not yet discussed in this memo.

6.  IANA Considerations

There are no IANA considerations in this memo.

7.  References

7.1. Normative References

7.2. Informative References

Appendix A.  Copyright

Copyright (C) Informed Control Inc. (2007).

This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, AND THE ORGANIZATION HE/SHE REPRESENTS DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Author's Address