Difference between OSB Layer and SOA Suite Layer

Difference between OSB Layer and SOA Suite Layer
example for the difference. Imagine a mountain hillside or valley kind of stretch of nature, and then imagine a straight road followed by a set of twisties. And you are given a choice of vehicles, a HUMMER and FERRARI. Which one would you choose on which terrain? Similarily, BPEL can do everything that an OSB can do, but it is meant for heavy weight orchestrations and stateful process, esp. long running(HUMMER). While OSB is meant for simple message routing, a bit of enrichment and tranformation, coupled with virtualisation. Now all these are light weight functions, which gives OSB the speed it needs(Ferrari).
Coming to your question, why two different tools? Well OSB was the recent aquisition to Oracle stable, from the erstwhile Aqualogic, ALSB. Whereas Mediator was csrried over from Oracles service bus, commonly called OESB.
Now based on, whether should you use both the toolsm well, thats upto your client actually. Are they rich enough to afford two licenses, then hell ya, go ahead with it. But most of the OSB task Mediator can do, thus you end up using a single license.
The major difference between OSB and SOA Suite would be that OSB is stateles while SOA Suite can maintain the state in Database. Also comparing OSB with SOA suite is not worth it since SOA Suite has got different components within itself like BPEL, Mediator, Business Rules ,Human Workflow etc which can be used to build a composite application. OSB could be very well compared to Mediator component of SOA Suite, which performs more or less similar activities, Mediator performs within the boundary of SOA Suite composite, while OSB performs the same activity independently.
There are instances where we use both OSB and SOA Suite within a single application, the benefits of which are explained in this pdf. http://www.oracle.com/…/maximizing-benefits-oracle-soa-1506…
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