Operation - An operation is a specification of a transformation or query that an object may be called to execute. It has a name and a list of parameters. [The Unified Modeling Language Reference Manual, pg 369]
Interface - A named set of operations that characterize the behavior of an element. [The Unified Modeling Language Reference Manual, pg 310]
OGC Web Service - A collection of 1 or more operations, including GetCapabilities. If any operation is part of an interface, all required operations of that interface must be included.
GetCapabilities - An operation returning an XML description of all operations instantiated in a given OGC Web Service instance.
OGC Basic Service Model - A model describing Common Elements and the GetCapabilities operation.
OGC Web Service Implementation Specification- A document describing one or more operations or interfaces that must conform to the OGC Basic Service Model.
Service Registry - A searchable collection of OGC Web Service metadata