RDF Revisited

Resource
The Resource Description Framework (RDF) is a standard (technically a W3C Recommendation) for describing resources.

Statements
Each arc in an RDF Model is called a statement. Each statement asserts a fact about a resource. A statement has three parts:

• the subject is the resource from which the arc leaves 
• the predicate is the property that labels the arc 
• the object is the resource or literal pointed to by the arc 

A statement is sometimes called a triple, because of its three parts.

RDF Syntax

• RDF/XML
• N-triple
• N3
• Turtle
• JSON
• TRiX

Sometimes it is not convenient to draw graphs when discussing them, so an alternative way of writing down the statements, called triples, is also used. In the triples notation, each statement in the graph is written as a simple triple of subject, predicate, and object, in that order. Example:

• <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/creator> <http://www.example.org/staffid/85740> .
• <http://www.example.org/index.html> <http://www.example.org/terms/creation-date> "August 16, 1999" .
• <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/language> "en" .

TIPS: 

Q: What is the difference between rdf:ID and rdf:about ? 

A: In RDF/XML, the subjects of statements are organized into node elements, which use attributes such as rdf:about and rdf:ID to set the subject for a collection of statements about that subject. Rules govern how the actual RDF subject URIs are constructed from these attributes, but there is plenty of room for confusion, and even instability, in the parsing results from environment to environment, if you're not careful. Read more here