Interface to RDF Datasource

Why the interface of Datasource provided through nsIRDFDatasource is so 
complicated ?

I'm thinking of 2 things :

- why is there several query functions (ArcLabelsIn/Out, GetTarget, 
GetSource...), where one function could do the same ? (as in RAP (a php 
librairy for manipulating RDF)

function find(a,b,c)

where a,b,c could be null. Find could return a nsISimpleEnumerator 
holding Triples. Access to triples would need 3 functions 
(getSubject/Predicate/Object).

- Decisions should be taken to whether the truth statement should be 
used or not.

Valentin