Adenine: A Metadata Programming Language
Metadata in the Haystack environment is expressed according to the Resource Description Framework (RDF) (RDF, 1998). In essence, RDF is a format for describing semantic networks or directed graphs with labeled edges. Nodes and edges are named with uniform resource identifiers (URIs), making them globally unique and thus useful in a distributed environment. Node URIs are used to represent objects, such as web pages, people, agents, and documents. A directed edge connecting two nodes expresses a relationship, given by the URI of the edge.