Newbie's question on similarity between two entities

[Leonidas Lymberopoulos]

Hello,

I am new to Semantics and I would like to know if SPARQL or some other  
query language/engine supports some kind of similarity metric for a given  
query.

For example, a metric could be the path length between the two objects I  
am trying to find their similarity, e.g. path_lenght = f(X,Y) where X, Y  
are two entities belonging to a schema.

Also, apart from the path length is there support for some other metric  
indicating how "similar" two entities are given a schema?

Thank you in advance,

Leonidas