The Resource Description Framework (RDF) is a language that is used to represent information about Web resources. RDF is intended for situations in which this information is processed by applications, rather than being displayed to users. RDF provides a common framework for expressing this information so that it can be exchanged between applications without loss of meaning. Since it is a common framework, application designers can take advantage of the availability of common RDF parsers and processing tools. The ability to exchange information between different applications means that the information may be made available to applications other than those for which it was originally created.
RDF uses Uniform Resource Identifiers to identify services, and describes Web resources in terms of simple properties and property values. A basic concept of RDF is the statement which contains a specific piece of information about a Web resource. An RDF statement can be broken into three parts, a subject, a predicate, and an object. The subject defines the Web resource for which the information is stored, the predicate defines a characteristic, or property that you want to gather information about on the subject, and the object contains the property value for the predicate. For more information, see What Is an RDF Subject?, What Is an RDF Predicate?, and What Is an RDF Object?.
The subject-predicate-object structure is known as a triple. Many RDF parsers break these statements into their component parts so that the data that the triple stores can be more easily processed by other operations. Parsers also frequently create a graphical representation that is to be parsed into simple statements about Web resources as a graph of nodes and arcs that represent the resources, their properties, and their values.
RDF documents are written in an XML-based language, known as RDF/XML. For more information about the syntax of RDF/XML, see the W3 Consortium RDF Web site at http://www.w3.org/rdf/. The following simple RDF document contains one statement:
<?xml version="1.0"?>
<rdf:RDF xmlns:csf="http://schemas.microsoft.com/connectedservices/pm#" xmlns:owl="http://www.w3.org/2002/07/owl#" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
<rdf:Description rdf:about="urn:upn_abc">
<csf:E-mail-Address>syed@contoso.com</csf:E-mail-Address>
</rdf:Description>
</rdf:RDF>
One triple would be generated from this document and a group of one or more triples is called an RDF graph. Some RDF parsers display RDF documents graphically after they have parsed them. The following figure represents a graphical image of this RDF document.
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The oval represents the subject of the triple, the arrow with the URL represents the predicate, and the rectangle represents the object.
Connected Service Framework (CSF) Profile Manager uses RDF blank nodes to cluster related predicates and objects as sub-properties of a named subject. For example, if you define an address subject, you can use a predicate to link it to a blank node. You can then use the blank node as a subject for several sub-properties of the address subject, such as street, city, state, and postal code properties. For more information, see What is an RDF Blank Node?
The existence of an RDF statement in the Profile Manager is dependent upon the input that the Profile Manager receives in a CreateProfileRequest message. There are only as many RDF statements (triples) for a given profile as you submit to the Profile Manager in the request. For example, if your company offered local phone services as a base service, with call waiting and voice mail as optional services, if a user only purchased the base service, there would be no RDF triples stored in the PM database that held information for that user about the call waiting and voice mail services. For more information, see What is an RDF Vocabulary?
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