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RE: Messaging Service Layer

From: Assaf Arkin <arkin@intalio.com>
Date: Mon, 17 Feb 2003 14:11:29 -0800
To: "Anne Thomas Manes" <anne@manes.net>, "Walden Mathews" <waldenm@optonline.net>
Cc: <www-ws-arch@w3.org>

How about defining what 'application' means?

When you write an application that uses an XML parser you typically
understand the application to be receiving an infoset, a tree of elements,
character data and attributes.

When you read the XML specification the application is actually the XML
parser which recieves a set of tokens (open element, end element, text,
CData, etc). The application that the XML spec is talking about is not the
application that the DOM spec is talking about, though the former does
contain the later.

At least in my understanding IETF talks about applications in the sense that
an FTP server or an HTTP server is an application. What we refer to as
application in the Web service world is a few layers about. The protocol for
this application is the 'purchase order management' protocol, something that
lives in the domain of Web service choreography.

The OSI model assumes more layers in the stack. The stack would contain the
HTTP server, the session management, the authentication, etc. It will
actually do all the WS layers inside the upper OSI layers. The application
would be the Web service application.

Similarly, in the Windows/UNIX/Linux world we build applications to handle
low-level protocols, such as HTTP, JMS, IIOP. In the mainframe world we
build applications to handle business-level protocols, services such as
transport, queuing, sessions are handled by the operating system.


> -----Original Message-----
> From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> Behalf Of Anne Thomas Manes
> Sent: Monday, February 17, 2003 1:25 PM
> To: Walden Mathews
> Cc: www-ws-arch@w3.org
> Subject: RE: Messaging Service Layer
> Please recognize that the term "transport" has different meaning in
> different circumstances. When talking about the OSI 7-layer model,
> "transport" refers to level 4, the transport layer (e.g., IP).
> But when you
> pop up out of the network protocol world into the application domain,
> "transport" doesn't have such a strict meaning. Many people use
> the term to
> mean "the network protocols that I use to transfer my message" -- which is
> equivalent to the entire OSI 7 layer stack. An application's
> access to this
> "transport layer" is through level 7, the application layer. Hence
> applications think of level 7 as the "transport layer".
> TCP/IP isn't an application layer protocol. It's at levels 5 (TCP) and 4
> (IP). An application can't just use TCP/IP. It needs an application-layer
> protocol to access the network. Something like HTTP, SMTP, IIOP, etc.
> >From the network's perspective, SOAP (as with most middleware
> systems) is an
> application. As with any other application, it accesses the
> network using an
> application layer protocol. Unlike other middleware systems, SOAP has been
> designed so that it can use any application layer protocol to access the
> network. So it can use HTTP, SMTP, IIOP, etc. as its "transport".
> We could build an entirely new application layer protocol for
> SOAP, but why
> would we want to? This "transport"-independence is one of its
> most valuable
> features. It's not so much a matter of firewalls. It's that **you
> don't have
> to install a new network protocol to use SOAP.** You can just use what
> already there -- e.g., HTTP.
> Anne
> > -----Original Message-----
> > From: Walden Mathews [mailto:waldenm@optonline.net]
> > Sent: Monday, February 17, 2003 12:09 PM
> > To: Anne Thomas Manes
> > Cc: www-ws-arch@w3.org
> > Subject: Re: Messaging Service Layer
> >
> >
> > > The topmost level of the OSI stack (Level 7 - the application layer)
> > > represents the network layer (application protocol) that
> > applications use
> > to
> > > access the network. HTTP sits in Level 7. That's why we view
> HTTP as the
> > > "transport" layer. It is the OSI Level 7 application protocol
> > that we use
> > to
> > > access the network.
> >
> > If you want a transport, why don't you use TCP?  Because of firewalls,
> > right?
> > But since firewalls have to be upgraded to understand what's
> buried inside
> > SOAP
> > messages and all that, why not just bite the bullet and decide to
> > do things
> > right in the first place?  Where, in the space of the WSA, is
> > there anything
> > remotely echoing this "do it right" sentiment?  The layers of
> > bastardization
> > are,
> > frankly, discouraging.
> >
> > Walden
> >
Received on Monday, 17 February 2003 17:12:54 UTC

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