SOA layers
One of the major strengths of a SOA is the independence of its own architecture from the system architecture. Hence, SOA layers as defined by [KRA07] or [MAS07] cannot be mapped directly to traditional layers of a tier-architecture. As shown in [1], a SOA can be divided into four layers. Nevertheless, a SOA could also consist of two or three layers. This means that this layered model does not necessarily need all four layers in order to be ‘complete’ since only some service types are a mandatory part of a SOA.
- The enterprise layer represents the highest layer of a SOA. It includes application frontends as well as public enterprise services. Subsequently, most of the communication flow is directed to users as well as applications from inside and outside the enterprise. As shown in figure 07, some of these services could run for instance on an application server while the others run on a web server. This shows that SOA layers do not correspond to system layers because they represent a horizontal as well as a vertical kind of slicing.
- Process knowledge is mainly situated at the process layer in terms of process centric services. As mentioned earlier process control can also be maintained by application frontends. In this case the process layer would also contain application frontends. An example for a [[services|process centric service] would be a Business Process Execution Language (BPEL) process running as a service on an application server (see [1]).
- Intermediary services based at the intermediary layer act as technology gateways, adapters or facades for other services. As described earlier they can also add functionality to other services (i.e. adding functionality in terms of an additional algorithm to a logic-centric service situated at the basic layer). These services could be deployed directly at the host or at an application server.
- Data-centric and logic-centric basic services are situated at the last layer called basic layer. Hence, this layer contains the business logic as well as access to the relevant data and is therefore of high importance. Like the previous three SOA layers its services can basically run on any system without affecting the design principles of SOA layers.
Letzte Änderung: 11.05.2009, 16:26 | 366 Worte