RDF query and RDF storage in memory

Hi List:

I have been studing RDF and following the discussion in this list for some
time. The concept of RDF is very appealing and I want to use it in my
applications, not specifically to *discover* resources on the web but first
mainly for integration of the different data I have. In the past I used XML
to just dump the data to XML document. But I want to bring some semantics to
this data and I think rdf is the way.

There are some implementation of RDF [parser] I found which are based on SAX
parser. But they are very basic and I could not find an answer to a
practical problem I have - how do I implement RDF, so that I can store the
whole RDF document in memory (kind of RDF DOM), use standard RDF query to
'query' it?

The second problem is more of a standardization problem. For example there
is a big diference bewteen the RDF Query Specification
(http://www.w3.org/QL/QL98/pp/rdfquery.html) and the query language used in
rdfDB project (http://web1.guha.com/rdfdb/query.html). Can someone explain
if there is "an accepted" query language specification?

My first problem is in a way related to the habit using XML. In XML we can
put everything in memory in a tree structure. But RDF is based on triples.
How can I store them for efficient querying? Does anyone know some links for
'dummies'?

Any information is welcome? 
Thanks in advance.

regards,
Ayalew Kassahun