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RE: What are web services ?

• To: 'Ken North' <kennorth@s...>, xml-dev@l...
• Subject: RE: What are web services ?
• From: "Bullard, Claude L (Len)" <len.bullard@i...>
• Date: Tue, 31 May 2005 15:14:24 -0500

The other way to say it is the sender does not block and wait.
What some look for that might not be there is store and forward, 
guarantee of delivery given UDP, and so on (it doesn't have to 
be HTTP but...).

The real killer in bidding web services is the lack of performance 
guarantees.  Often, an interface comes with a performance requirement 
that a query return in a second or less.   It is common now to see 
requirements for publish/subscribe models for systems where the 
publisher has to be queried for its state (available, degraded, etc.)
and the queried unit has to answer in a second or less.  The proper 
response is to take exception to the requirement to use web services 
because the performance requirement is mission critical.  It is 
important not to put the cart before the horse (bid a technology 
instead of bidding the mission requirement).  MQSeries isn't dead yet.

We won't know the state of practice and the viability of web services 
until a few mission critical systems are procured based on this 
technology.  Some agency out there gets to be the first penguin. 
Hopefully, they will publish results for others to use.

len


From: Ken North [mailto:kennorth@s...]

>> Has the ability to perform its functionality synchronously or
asynchronously

To explain synchronous and asynchronous communication, I use a telephone
example. If someone answers when you call, that synchronous. If no one
answers
but you leave voicemail, that's asynchronous.

SOAP supports synchronous and asynchronous messaging.  Using RPC-style
messaging, communication is synchronous and the service provider and
consumer
maintain state. Document-style SOAP messaging (XML document in the payload)
supports asynchronous messaging because you can encapsulate state
information in
a document.

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