Services

1、A service is the IT realization of some self-contained bussines functionality.

2、By focusing on the business aspects, a service hides technical details and allows business people to deal with it.

3、Technically, a service is an interface for (multiple) messages that are exchanged between provider(s) and consumer(s).

4、The complete description of a service form a consumer's point of view (signature and semantics) is called a "well-defined interface" or "contract ", A contract is agreed individually between a certain provider, and a certain consumer, and usually includes nonfunctional aspecsts such as SLAs .

5、There are serveral attributes that services may hava.According to my understanding, they are situation-dependent; services will almost always have different attributes, and should be classified according to those attributes.