Databases Reference
In-Depth Information
Reuse in place
A final major distinguishing feature for SOA is the concept of reuse in place. Most
reuse technologies in the past have focused on reuse through libraries, at best
sharing a common implementation on a single machine through the use of dynamic
link libraries. SOA focuses not only on reuse of the code functionality, but also
upon the reuse of existing machine resources to execute that code. When a service is
reused, the same physical servers with their associated memory and CPU are shared
across a larger client base. This is good from the perspective of providing a consistent
location to enforce code changes, security constraints, and logging policies, but it
does mean that the performance of existing users may be impacted if care is not
taken in how services are reused.
Client responsibility in service contracts
As SOA is about reuse in place of existing machine resources
as well as software resources, it is important that part of the
service contract specifies the expected usage a client will make
of a service. Imposing this constraint on the client is important
for efficient sizing of the services being used by the client.
Service Component Architecture (SCA)
We have spoken a lot about service reuse and composing new services out of existing
services, but we have yet to indicate how this may be done. The Service Component
Architecture in SOA Suite is a standard that is used to define how services in a
composite application are connected. It also defines how a service may interact
with other services.
