Task: Design Service Contract
Design contractual information about service
Disciplines: Service-Oriented Design
Purpose
The purpose of the service contract is to inform the consumer about the service and how to use it.
Main Description

Assuming standardization on Web services, then contract definition consists of three tasks:

Desgin Message Schema

Create WSDL

Define Policies

Key Considerations
XML and Web services are the most likely contractual standards, but others could be used instead.
More Information