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Arnon Rotem-Gal-Oz

Dr. Dobb's Bloggers

Layers and SOA

February 24, 2008

I've been a little quiet, what with a visit to Barcelona (GSM World Congress), and then some pressure at work (making up for the lost time :) ). Hopefully I can now get back to regular blogging.

In the previous post, I mentioned a couple of questions on SOA and layers Udi left on an older post I made:

1. How does this [layers - ARGO] play with two services talking with each other? One pubs to the other's subs?The other requests to the first's response?

2. How valuable is the layered abstraction?

1. As I explained in the previous post. Layers does not necessarily mean unidirectional relation from a top layer to a lower level one -- it does mean that a layer can only know a layer that is diretly above or below
it. In other words, the bidirectional interaction between two services -- i.e., the request, reactions, events, etc. flowing between them -- do not violate the layered style constraints.

2. So, how valuable is the layered abstraction to SOA? The short answer is -- very :). Again, as I mentioned in the previous post, the main reason layers don't seem that valuable is because they've been misrepresented and misused. Layers bring added flexibility to SOA. The fact that a service or any other SOA component cannot see beyond the next layer enables things like the ServiceBus, Edge Component, Service Firewall, etc. Without layers it would be harder to have autonomous services as other services could (potentially) have access to the innards of the
service adding more coupling and preventing independence.

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