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Re: Application Protocol Definition (was RE: Visibility (was Re: Intr oducing the Service Oriented Architec tural style ...

From: James M Snell <jasnell@us.ibm.com>
Date: Thu, 27 Feb 2003 08:00:21 -0800
To: "Burdett, David" <david.burdett@commerceone.com>
Cc: "'Assaf Arkin'" <arkin@intalio.com>, "Burdett, David" <david.burdett@commerceone.com>, Mark Baker <distobj@acm.org>, www-ws-arch@w3.org, www-ws-arch-request@w3.org
Message-ID: <OF83CB6713.DD06149C-ON88256CDA.0056C50F-88256CDA.0057EC6C@us.ibm.com>

Just my 2 cents thrown in from the spectator stands...

I agree that "application protocol" is not the right term for the 
collection of "slightly more specialized but still general protocols".  I 
often refer to those as Utility Protocols rather than Application 
Protocols which should focus on the abstract business operations and data 
needing to be exchanged.

The order I would recommend is:

1. Network Protocols
2. Communication Protocols
3. Messaging Protocols
4. Utility Protocols
     a. Business Transaction Protocols
     b. Discovery Protocol
     c. Negotiation Protocol
     .... <etc> ...
5. Business Protocols
6. Application Protocols

- James Snell
     IBM Emerging Technologies
     jasnell@us.ibm.com
     (559) 587-1233 (office)
     (700) 544-9035 (t/l)
     Programming Web Services With SOAP
         O'Reilly & Associates, ISBN 0596000952

     Have I not commanded you? Be strong and courageous. 
     Do not be terrified, do not be discouraged, for the Lord your 
     God will be with you whereever you go.    - Joshua 1:9



"Burdett, David" <david.burdett@commerceone.com>
Sent by: www-ws-arch-request@w3.org
02/27/2003 03:33 AM

To
"'Assaf Arkin'" <arkin@intalio.com>, Mark Baker <distobj@acm.org>, 
"Burdett, David" <david.burdett@commerceone.com>
cc
www-ws-arch@w3.org
bcc

Subject
Application Protocol Definition (was RE: Visibility (was Re: Intr oducing 
the Service Oriented Architec tural  style ...





Arkin 

You said ... 

>>> This of course doesn't help much, because we've just introduced three 
different protocols, one described by HTTP, one described by WSDL and one 
described by WSCI (just as an example). Again as with synch/asynch, this 
is all a matter of applying a definition in the proper context.<<<

It might not help, but it is real life. You do have multiple protocols 
operating in combination at different "layers", for example (not sure this 
list is complete or the names are right)

1. Network infrastructure protocols, e.g. TCP/IP 
2. Communication protocols, e.g. HTTP 
3. Messaging protocols, e.g. ebXML Messaging or WS-RM 
4. Business protocols, e.g. Order placement protocol that defines sequence 
of exchange of business documents 

You can also have other more slightly more specialized but still general 
"protocols", e.g. 
5. Two phase commit, e.g. Business Transaction Protocol 
6. Discover protocol, e.g To discover a WSDL or Schema definition (REST 
can work well here) 
7. Negotiation protocol, e.g. To negotiate which combination of protocols 
1 through 4 to use in a specific instance 

... we could probably go on ...

The point is just calling some or all of these an "Application Protocol" 
is, IMHO, insufficiently precise. 

Do you think we should try and define these types of protocol and what 
they mean in more detail? 

David 

-----Original Message----- 
From: Assaf Arkin [mailto:arkin@intalio.com] 
Sent: Wednesday, February 26, 2003 12:13 PM 
To: Mark Baker; Burdett, David 
Cc: www-ws-arch@w3.org 
Subject: RE: Visibility (was Re: Introducing the Service Oriented 
Architec tural style, and it's constraints and properties. 

> On Wed, Feb 26, 2003 at 03:18:48AM -0800, Burdett, David wrote: 
> > <DB>We need to define what we mean by an "application" if you mean it 
is 
> > anything above the transport layer, then you are correct but 
> really I think 
> > the layers are typically: Operating System, App Server, "Web Services 
> > Middleware", Application. 

How about: 

Application - A program designed to assist in the performance of a 
specific 
task, such as word processing, accounting, or inventory management 

Now the only question is 'what application are we talking about?' 

Are we talking about the HTTP or FTP server? In this case HTTP and FTP are 

the application protocols. 

Are we talking about accounting? In this case the accounting protocol is 
the 
application protocol. 

Is it possible to have an application on top of an application on top of 
an 
application? How about my accounting application running inside a WS
container (in itself an application) implemented inside an HTTP server (in 

itself an application). Is that possible? 

This of course doesn't help much, because we've just introduced three
different protocols, one described by HTTP, one described by WSDL and one 
described by WSCI (just as an example). Again as with synch/asynch, this 
is 
all a matter of applying a definition in the proper context. 

arkin 

> 
> The *critical* thing that one has to accept in order to understand REST, 

> is that application protocol methods are the same as operations in an 
> API, i.e. at the same layer of the stack as "getStockQuote" or 
> "purchaseBook".  If you just take this as a given for a moment, you'll 
> see that all the arguments I've ever made on this subject become a big, 
> complex, yet entirely self-consistent description of much of Web 
> architecture, and indeed several other Internet scale architectures.  If
> you don't accept it, then I probably come off as a loon, which I 
> completely understand because I thought the same thing of some guys who 
> saying that to me back in 97/98 (Dan Connolly and Roy Fielding, FWIW). 
> 
> So, a *rhetorical* question for those of you who don't believe that 
> GET is at the same layer as getStockQuote; what would you call a 
> protocol that does have a "getStockQuote" method?  Note; "application
> protocol" is already taken. 8-) 
> 
> MB 
> -- 
> Mark Baker.   Ottawa, Ontario, CANADA.        http://www.markbaker.ca 
> Web architecture consulting, technical reports, evaluation & analysis 
Received on Thursday, 27 February 2003 11:10:51 GMT

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