While nearly every record type in the registry represents a type of resource - Service, Endpoint, Interface - these coarse grained resources are composed of finer elements. Each Service is defined eventually by one or more WSDLs. A WSDL may contain a service element. Each endpoint represents a live service implementation which can be located through the port element of a WSDL service. Each WSDL service refers back to a WSDL binding to which its messaging and transport mechanisms conform. And each binding refers back to an Interface, also known as portType under the WSDL specification.
If you are familiar with WSDL and Web services you know that an Interface defines operations that consume and produce messages, most often structured according to the SOAP specification. You also know that SOAP is a subset of XML and XML Schema is a parsable Meta-type standard used for defining XML document structures and complex types. These definitions provide us with another realm of resources that need to be mapped into, recorded in and managed by a Registry.
Fine Grained Resources
WSDL portType - a record of an actual portType (Interface) element found in a WSDL document.
WSDL binding - A record of an actual binding element found in a WSDL document.
WSDL service - A record of an actual service element found in a WSDL document.
WSDL port A record of an actual service/port (Live endpoint) element found in a WSDL document.
XSD - an XML document that defines documents and/or types reused throughout the system.
XSLT - an XML document that describes how to transform one or more XML document types into another XML document or even many others.
XML - A constant XML document that can be reused throughout the system.
Registry records representing these resources of course contain more information than resource locations. They may also track and document states, provide keyword search capabilities, classifications, and add descriptive details.