Difference between Agents and (Semantic) Web Services

Hi,

Pardon me if this is a very naive question, but someone can please tell me
crisply the difference(s) between software agents and (semantic) Web
services? I have been trying to find out a comparison between them over the
Web and came across the following:
http://portal.acm.org/citation.cfm?id=873262, which unfortunately did not
suffice my query to its entirety.

I look forward to your inputs.

Thanks,
- Jyoti




-- 
Jyotishman Pathak
WWW: http://www.cs.iastate.edu/~jpathak