<<There is a discussion on Linked-In entitled SOA in an Offline World.
The discussion has a technical focus: What kind of technology
architecture to use with unreliable or intermittent network
communications. There are some design patterns that may support
intermittent connection, such as decoupling and asynchronous
communications, and these patterns may be appropriate in a range of
situations including military and medical.
A broader architectural question is whether we can use layering to hide
these technical issues from the business-facing services in the layers
above. In an ideal world, we would have a disruption-tolerant service
platform, and the core business services and applications can then
operate as if we had perfect and permanent connectivity.
In the 1990s, Peter Deutsch and James Gosling identified Eight Fallacies
of Distributed Computing - invalid assumptions that inexperienced
designers make when designing distributed systems. See Arnon Rotem
Gal-Oz
<http://www.rgoarchitects.com/nblog/2006/05/21/FallaciesOfDistributedComputingExplained.aspx>
and Paul Vincent (TIBCO)
<http://tibcoblogs.com/cep/2008/12/16/the-eight-fallacies-of-distributed-computing/>.
These include the assumption of perfect and permanent connectivity.
By the way, Tim Bass
<http://www.thecepblog.com/2008/12/18/the-fallacy-of-fallacy/> questions
whether anyone nowadays suffers from these fallacies. I think he's got a
point, but perhaps the problem here is in the word "fallacy". If you ask
a designer if he believes connectivity is going to be perfect, he will
almost certainly say no. But if you inspect his designs, however, you
may well find that he has failed to allow adequately for imperfect
connectivity. Not so much a failure of belief as a failure of attention.
So the important question here is - can we compensate for the
imperfections of distributed systems by having a really clever
architecture, supported by really clever technology, so that the
applications can operate as if we didn't have any of the problems of
distribution at all? Some people may well believe that to be possible,
either now or in the foreseeable future.
I don't think it's so easy. I have long argued that SOA needs to embrace
three-valued logic
<http://rvsoapbox.blogspot.com/2004/06/beyond-binary-logic.htm>. If this
is done properly, it would make the whole architecture
disruption-tolerant, not just the underlying layers. We also need to
understand how disruption-tolerance affects the behaviour of the whole
business-facing system. Not just technology then.>>
You can read this at:
http://rvsoapbox.blogspot.com/
Gervas
