Lowest level constituent of the logical architecture, in an SOA style
Introduction to the notion
The definition and discussion hereafter apply only to the logical aspect. It is the notion of service that characterizes the Service Oriented Architecture.
The importance of the notion of service is such that it needs to be defined from three angles: what it is, what it does and what it will become.
What is a service?
The service is the lowest level constituent of the logical architecture. Hence the term “Service Architecture.” The service is the atom or elementary constituent of the logical construction of a system.
What does it do?
A service is an elementary response of the system to a request for information, for an action or for a transformation. This prohibits both direct data access and remote operations.
Where does a service come from and what does it become?
Logical services are the design units of logical architecture and are derived from the preceding models (semantic and pragmatic). They are implemented as software components in the chosen technology. The software components are located on one or several machines and can be activated at execution time.
How can we identify a service?
One can use two complementary approaches:
- Top down: the logical components are derived from the semantic and pragmatic models.
- Bottom up: the logical model is completed by rereading the functional details expected (use cases or activities of business processes).
Each service has a logical identifier, unique in the system (it should be meaningful).
Documentation of logical services
The logical services are documented by:
- a ‘request of service’ form, standardizing communication between different IT departments;
- a description note, more complete.
These forms can be integrated in the modeling tool, using a UML profile.