When discussing the Resource Description Framework (RDF)
specification, we’re really talking about two different specifications—a
Syntax Specification and a Schema Specification. As described in Chapter 3 and Chapter 4, the Syntax Specification shows
how RDF constructs relate to each other and how they can be diagrammed in
XML. For instance, elements such as
pstcn:bio are used to describe a specific
resource, providing information such as the resource’s type and the author
of the resource. The different namespace prefixes associated with each
element (such as
pstcn:) represent the schema that particular
element is defined within.
In the context of RDF/XML, a vocabulary or schema is a rules-based
dictionary that defines the elements of importance to a domain and then
describes how these elements relate to one another. It provides a type
system that can then be used by domain owners to create RDF/XML
vocabularies for their particular domains. For example, the
pstcn:bio element is from a custom vocabulary
created for use with this book while the
rdf:type element is from the RDF vocabulary.
These are different vocabularies and have different vocabulary owners, but
both follow rules defined within the RDF Vocabulary Description Language
1.0: RDF Schema.
However, before getting into the details of the RDF Schema, consider the following: if RDF is a way of describing data, then the RDF Schema can be considered ...