SOA is based on four important concepts:-
• Boundaries are well defined
In SOA, everything is formalized. The client who is consuming the service does not need to know how the implementation of the service is done. If you look at some old methodologies of communication like DCOM. Any changes at server level the client also has to change. Therefore, the server and client implementation was so much bound that changes need to be done at all places. In SOA, the rule is if you do enhancement you do not need to change anything at the client. SOA based application only understands that there is an end point, contract, and bindings.
• Services evolve
Change is the law of
nature and services will evolve. In SOA, services can be versioned and
you can host those services in new ends. For instance, you have a
service called as “Search Tickets (Ticket Number) “which gives details
based on Ticket Number and its exposed on end point “ep1”. Tomorrow you
want make your Search Tickets service more useful by also providing an
extra option of allowing him to search by passenger name. Therefore, you
just declare a new end “ep2” with service “Search Tickets (Ticket
Number, Passenger Name)”. So the client who is consuming the service at
end ep1 continues and at the other end, we have evolved our service by
adding new ends ep2.
• Services share only schemas and contracts
Services use Schemas to
represent data and contracts to understand behavior. They do not use
language dependent types or classes in order to understand data and
behavior. XML is used to define schemas and contracts. Due to this,
there is not heavy coupling between environments.
• Service compatibility is policy basedPolicy describes the capabilities of the system. Depending on policies, the service can degrade to match the service for the client. For instance your service needs to be hosted for two types of client one which uses Remoting as the communication methodology while other client uses DCOM. An ideal SOA service can cater to both of them according to there communication policies.