Question on .slib file extension

Hi there!

First Question:
Can anybody tell me what a .slib file is?
My rough understanding is that this is the file extension
for an "interface timing specification" model given by tools
such as Synopsys' PathMill. Please correct me and elaborate
if I am incorrect with this.

Second Question:
With the defintion of a .slb file sorted out with a response to Qn1,
how does this
..slib file differ from a Synopsys .lib timing model file?

I know that this group is a user forum for synthesis,
however, I am unable to locate a usergroup
dedicated to Synopsys products.  Hence I am placing my question here.

Thanks for the help.

Cheers
SB