Thursday, May 13, 2004

Pure Abstraction

RDF as data abstraction "Mozilla's central interface for dealing with data is RDF. RDF datasources can have any implementation they like behind them. However, they must provide the information through the nsIRDFDataSource interface that specifies a graph API of nodes and edges. Once this is done, any client can operate with the datasource without reference to the domain objects, methods, or underlying implementation. You just need to know how to manipulate a graph, and you're set.

This is the true potential of RDF. It's not a substitute for databases or XML. RDF is a directed labelled graph. It hides information and provides a data interface which can be used to aggregate multiple datasources that can be themselves RDF datasources. This is the purest data abstraction. Theoretically, if you weren't worried about performance you could access an RDF datasource and not know or care whether you're accessing a database, a web service, or both. The RDF datasource might even optimize its data structures based on what your queries or iteration patterns have been, in much the same way as hotspot compilation optimizes algorithms in the JVM.

A good question at this point is whether RDF is as powerful an API as JDBC. The answer is yes, or not quite. RDF is only a data structure, and there are several APIs for manipulating that data structure. The most well known implementation is Jena. Jena's API for manipulating RDF graphs is very powerful, and encompasses most things you would find in JDBC, such as transactions, a query language, and prepared statements."
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