Joshua,
Let me see if I can help explain some:
Joshua Jackson wrote:
Thanks for the article. I kind of get idea now. This is what I get from it:
SCA is a kind of glue code for glueing pool of apps to be used by
another apps. So our new apps will connect to SCA and SCA will connect
to these pool of apps. CMIIW.
Yes, SCA is at one level a way of connecting together sets of components
to build up your overall application. One of the great things is that
you don't have to code any information about what is connected to what
into your code. This is applied as configuration data - and so it
allows the data to be changed without changing the code - and it allows
the code to be reused in different configurations.
I don't quite understand. People out there compares SCA with JBI,
which is an ESB. :( And that's an insight that I get from those
articles you gave me too.
JBI is largely a way of putting a runtime together - where the runtime
involves components written using different technologies (eg BPEL and
Java). SCA is a way of putting applications together - where there are
potentially components written in different technologies and connected
by different technologies.
It happens that you could envisage running SCA applications on a JBI
runtime - ie JBI can provide the sort of runtime that SCA applications
can use.
HOWEVER, SCA does not depend on JBI at all - Tuscany, for example, does
not use JBI at all. Further - SCA can describe applications that aren't
written in Java and don't use a Java based runtime either (eg there is a
C++ runtime in Tuscany that can run components written in C++, Ruby and
other scripting languages).
One way to look at SCA is that it CAN be used as a programming model for
ESBs. SCA describes the components that run on the ESB and their
connectivity. You can have components that are message transformations
or the selection of a target service based on some rule, for example.
These are the sorts of things that ESBs do.
That doesn't mean that SCA is an ESB - just that it can be used to build
applications that run on an ESB.
Is Tuscany an ESB? Well, it could be ;-) - a funny half-answer.
I can do some of the things that an ESB does. But ESBs usually have
specialized component types that do things like message mapping -
Tuscany only has some of these today. On the other hand, anyone can
write new component types for SCA, so that anything needed could be
added to SCA.
One other point about SCA is that it is about distributed systems - most
ESBs are not like that. In other words, for SCA, different components
can run on different nodes in a network.
Is there anything I need to know in order for Tuscany to connect to AS400 ?
You need to know which communication protocol(s) you can use to talk
with the AS/400 - plus the appropriate addresses of endpoints relating
to the AS/400. So, maybe you're using JMS over MQSeries, or Web
services, or .....
Thanks in advance
Yours, Mike Edwards
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