We propose a structural approach to service composition using a relational model. We focus on structural aspects of service composition and apply the relational model. Services in our model are defined and organized by relations, and service manipulations such as service invoke and service composition, are achieved by relational operations to the corresponding relations. Since conventional relational algebra is insufficient for service management, we extend relational algebra and introduce a new θ-operator to deal with services.

We also explain how to achieve this model using a relational system to manage the database. Users utilizing this system, can access services with SQL, and it becomes easier for them to collaborate with data stored in relational databases and services.