Extensions to the RDF Model

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Literal Reification

The ability to make assertions about Literals is necessary. Literals either need to be resources, or there needs to be a resource for each Literal. With regards to implementation, the former poses the problem of representing literal text in the form of a URI. While RFC 2397 addresses this issue, the method it describes is limited by the length of the string to be represented. The latter does not suffer from string length issues, so it will be the approach of this model.

For the purpose of this specification, a resource is representative of a Literal. Any statement with such a resource as it's subject makes an assertion about a Literal, not the resource representing it.

The following formalization can be thought of as an extension to section 5 of the RDF Model and Sytnax Specification.

  1. There is an element of Properties known as RDF:represents.
  2. There is an element of Resources, not in Properties, known as RDF:Literal
  3. Reification of a member of Literals is an element r of Resources, representing the Literal, and the following statements:

    {RDF:type, r, RDF::Literal}
    {RDF:represents, r, x}
    where x is the Literal.

RDF Bundle Spec

In order to distinguish the RDF Model from an RDF Model, the latter will be referred to as bundles.

The following formalization can be thought of as an extension to section 5 of the RDF Model and Sytnax Specification.

  1. There is a set called Bundles. Bundles is the set of all subsets of
    (Resources \union Literals \union Statements).
  2. There is an element of Properties known as RDF:contains.
  3. There is an element of Resources, not contained in Properties, known as RDF:Bundle
  4. Reification of a member of Bundles is an element r of Resources, representing the Bundle, and the following statements:

    {RDF:type, r, RDF:Bundle}

    {RDF:contains , r, x}
    one for each element in the Bundle, where x is the Literal, Resource, or reified Statement.

    In addition, for each Statement in r, the triples making up it's reification are also in the reified member of Bundles.
    {RDF:type, st, RDF:Statement}
    {RDF:predicate, st, p}
    {RDF:subject, st, s}
    {RDF:object, st, o}


Devon Smith (smithde)(at)(oclc dot org)
Online Computer Library Center (http://www.oclc.org)
2001-05-31