Relation between OWL and OWL-S

Hi all, 
 I would like to know what is actually the relation between OWL-S and OWL?
How do I represent this relation in OWL-S? 
I will be more clear...for example, suppose that I have a service called
AirplaneCompany that searches for a ticket beased on some input parameters
and it belongs to a service composition called Travel. 

- How can I do automatic discovery in this case? I've read that the
automatic discovery in OWL-S is based on its input and outputs parameters,
so we can make a distinction between the services. 

But actually, how can I say that my AirplaneCompany service is a class in
OWL model? Where Can I put this relation in OWL-S? And also, where can I say
that AirplaneCompany is the same service that AircraftCompany, as we do in
OWL using equivalenceClass like:

<owl:Class rdf:ID="Aircraft">
    <owl:equivalentClass rdf:resource="urn:eg#AirPlane"/>

These relations exist? Or in OWL-S we can not say that? 

Thank you so much!
Daniela