RDF provides a basic way to represent data for the Semantic Web. We have 
      been experimenting with the query paradigm for working with RDF data in 
      semantic web applications. Query of RDF data provides a declarative 
      access mechanism that is suitable for application usage and remote 
      access. We describe work on a conceptual model for querying RDF data 
      that refines ideas first presented in at the W3C workshop on Query 
      Languages and the design of one possible syntax, derived from rdfDB, 
      that is suitable for application programmers. Further, we present 
      experience gained in three implementations of the query language.