[no subject]

Peter F., however, says SOAP headers already provide adequate
syntactical distinctness. Said another way,
what advantage is gained by having syntactically marking headers for
contexts to set them apart from all the other SOAP headers? I am
sympathetic to that question because I had hoped the TC would bound the
context header's intended area of applicability so that implementers (or
spec writers) can clearly tell when using a context header would be an
advantage and when the information should go into its own header. I
assume this group does not to put
every SOAP header module into a context header; that would violate the
semantic principle that distinctions must embody a "non vacuous
contrast."=20

Less loftily, I had presumed a tacit SOAP header processing model (maybe
a little beyond anything explicitly in the SOAP XMLP explicit
specification) in which the general SOAP message processor would check
to see if it had a SOAP-context-header handler and shove off what needs
to be done to that task module. OK, what does that module need to know
to do its job? So far I get the feeling that all it does is hand off to
a yet more specialized context handler for security context, transaction
context, session context, etc. The question of real interop is then
deferred from  whether we have the same SOAP header handler to whether
we have the same capabilities in subhandlers of the context header. If
all the specialized subhandlers reuse functionality present in the base
class soap context handler, so far it does not seem that very much gets
reused. (GET on URI?)

I am trying to be antagonistic here. I am simply trying to see what
general computational advantages attach to the context header proposal
so that I might explain it to a software architectural-design team.
Otherwise it is just another syntactial something or other to worry
about.



-----Original Message-----
From: Mark Little [mailto:mark.little@arjuna.com]=20
Sent: Friday, February 13, 2004 5:24 AM
To: Furniss, Peter; ws-caf@lists.oasis-open.org
Subject: Re: [ws-caf] Agenda for the demo application


Peter, I think we're about to start going round in circles here. What
your example does show is one of the benefits of WS-Context: the fact
that because context is standardised (I'm assuming it is), all users of
it (end-users, other specifications, whatever), have a well defined way
to scope (namespace) their contexts into their messages. Currently some
context information in apps. goes in the body of a message, which makes
it more difficult (slower) to locate.

Fairly obviously the users of ServiceContexts (e.g., the OTS) had to do
some work to use them, but the fact that they came along facilitated
interoperability for contexts. SOAP headers don't just contain context
information at the moment, and as I said above, don't even have to
contain context information. Addressing that is part of what we're
looking at. And then there's the composite nature of the context
augmentation that I mentioned previously.

But like I said at the start, I think we're not going to agree on this
(again). As Eric pointed out, of course you can do context today with
what's around, and what we're trying to do in WS-Context isn't
necessarily rocket science or re-inventing the wheel; it's agreeing on a
standard format for contexts that can be used by all specifications and
applications. From a purely syntactic perspective, I'd like to have my
SOAP documents with a well defined context element that's the same
whether it's conveying transaction, security or session-oriented data.

Mark.

----
Mark Little,
Chief Architect, Transactions,
Arjuna Technologies Ltd.
=20
www.arjuna.com

----- Original Message -----=20
From: Furniss, Peter=20
To: Mark Little ; ws-caf@lists.oasis-open.org=20
Sent: Friday, February 13, 2004 12:12 PM
Subject: RE: [ws-caf] Agenda for the demo application




Ok, maybe I have misunderstood. Let's try a little example (related to
one of the example scenarios), of what looks like a light-weight
context-using requirement and show what I meant about wrapping:

Users initiate web-service using tasks that may involve indeterminate
numbers of systems. To help with error tracking etc, each system is to
be told the users identity and some task-identification chosen by them
(or their initiating software). It's a benign environment and
masquerading won't benefit the attacker, so its just an assertion
Supporting systems can put this information in access and error logs,
printers could include it on a banner page etc. Sort of thing that might
be useful in academic computer services.

So the fields we need are, say,  username, a string; an identifier for
the task (could be string or uri); and  to allow username assignment to
be unambiguous and decentralised, identification of the naming authority
- a URI, given by the institution, company or isp. (There are various
other ways you could partition the information here)

But, to allow a receiver of this information to know what it supposed to
be, we need to have an identifier to say what it is - some unambiguous
value assigned by whoever defined this use -(a fictitious entity called
Webservices Things, who call this their "User Labelling" facility)

Now, if WS Things has bought into WS-Context, that last identification
is the "type", the task identifier will be the "context-identifier" and
username and authority-identifier will be additional elements, and
messages that are to be user-labelled will be like this:

<soap:Envelope xmlns:soap=3D"http://www.w3.org/2002/12/soapenvelope";>
<soap:Header>
 <ctx:Context
xmlns:ctx=3D"http://www.webservicestransactions.org/schemas/wsctx/2003/03=
"
>
=20
<ctx:context-identifier>http://pluto.ulcc.ac.uk/task/EJ4439kjsf9/prf</ct
x:context-identifier>
  <ul:Label
xmlns:ul=3D"http://webservicethings.org/util/userlabelling/2004/02";>
   <ul:user>cziwprf</ul:user>
   <ul:authority>http://ulcc.ac.uk</ul:authority>
  </ul:Label>
 </ctx:Context>
 ... other headers ...
</soap:Header>
<soap:Body>
 ... message body ...
</soap:Body>
</soap:Envelope>

(using my identity from when I was in that world :-)

Whereas if Webservices Things had decided not to go with WS-Context, the
user-labelled soap messages would be like

<soap:Envelope xmlns:soap=3D"http://www.w3.org/2002/12/soapenvelope";>
<soap:Header>
 <ul:Label
xmlns:ul=3D"http://webservicethings.org/util/userlabelling/2004/02";>
=20
<ul:task-identifier>http://pluto.ulcc.ac.uk/task/EJ4439kjsf9/prf</ul:tas
k-identifier>
      <ul:user>cziwprf</ul:user>
      <ul:authority>http://ulcc.ac.uk</ul:authority>
  </ul:Label>
 ... other headers ...
</soap:Header>
<soap:Body>
 ... message body ...
</soap:Body>
</soap:Envelope>

The thing is, not only is that exactly the same information, but WS
Things specification in the first case is no simpler or shorter.=20

You seem to be saying in "is the format of that element and how it can
be located in the header" that it is harder to locate the information in
the second case. But it's already in the header, and identified by the
top-element of the header and its namespace. It isn't scattered at some
random point in the message as a whole, because soap headers define
where to look.



Touching the IIOP ServiceContext comparison - ServiceContext alone
didn't make for interoperable transactions (say)- there also needed to
be the work of the OTS group to specify what went in a transaction
context. Their deliberations on how to transmit that context were
simplified because they could just say "its a Service Context" - if
they'ed done it earlier, they'ed have had to invent something of their
own.  But with the SOAP world, we started off with SOAP Headers (perhaps
in the knowledge of what was needed for IIOP) and there isn't a need for
another layer of the same.

The only virtue for WS-Context is if the other things it brings are
useful for many cases, and I've not seen evidence of that - those extra
features nearly all seem to be specific to particular uses.

Peter


-----Original Message-----
From: Mark Little [mailto:mark.little@arjuna.com]=20
Sent: 13 February 2004 10:41
To: Furniss, Peter; ws-caf@lists.oasis-open.org
Subject: Re: [ws-caf] Agenda for the demo application




CORBA ServiceContext corresponds more or less exactly to SOAP Header -
it is an opportunity to information to the main data message to support
a supporting or adjunct protocol. The particular adjunct protocol in
question is identified by a value of the ServiceContext or Header that
is unambiguous among the set of possible adjuncts - one of the neat
things about the XML world is that registration is devolved, so unlike
CORBA, there is no need for a central registry of header
identifications.
There is no difference between a propagated IIOP CORBA ServiceContext
that contains security and transaction information, from a propagated
XML WS-Context that contains security and transaction elements. The
point I was originally making was that prior to ServiceContext, you had
companies like Visigenic, Iona, IBM, HP, Nortel etc. propagating context
information in a proprietary manner and format simply because they had
no choice. Then ServiceContext came along and made interoperability a
possibility because it standardised that format and manner. As Eric has
pointed out already, that's pretty much what we're trying to do. =20
But I don't think there were suggestions of a hyper-service-context in
CORBA - a wrapper ServiceContext whose real meaning was determined by
the contained information. Each context travelled naked. (In fact, given
the registration requirement, a wrapper conceivably could have been
useful in CORBA allowing devolved registration, but that isn't needed
with SOAP and XML).
Maybe you've got a slight misunderstanding of what the WS-Context will
look like, or maybe I just can't see what your wrapper is all about. If
we consider pass-by-value for the context, then there'll be a context
element in the header for each context type (security, transactions,
replication, etc.) What we're defining is the format of that element and
how it can be located in the header. Seems like the same as locating the
ServiceContext in IIOP.

Once you've got the basic means of passing identified information, the
real fun is in the specification of the the adjunct protocol of course,
but that wouldn't be WS-Context but it's user - or a SOAP Header user,
or in the old world, a ServiceContext user, with its own interfaces and
methods, using the information received in the header/servicecontext.

WS-CF and WS-TXM fall into this category, I'd presume.

Mark.

----
Mark Little,
Chief Architect, Transactions,
Arjuna Technologies Ltd.
=20
www.arjuna.com


Peter
-----Original Message-----
From: Mark Little [mailto:mark.little@arjuna.com]=20
Sent: 12 February 2004 16:37
To: Furniss, Peter; ws-caf@lists.oasis-open.org
Subject: Re: [ws-caf] Agenda for the demo application


Peter, interesting discussion, but I think it comes down to utility,
ease of use and extensibility. If you look at CORBA for example, you
could probably make the same arguments for why ServiceContext shouldn't
have been added to the architecture and why existing schemes at that
time (vendor/specification specific) were fine. Only time will tell, of
course, but I believe that context is a basic requirement for all
distributed systems and WS-Context is definining a pretty good model for
Web services on which to build.

Mark.

----
Mark Little,
Chief Architect, Transactions,
Arjuna Technologies Ltd.
=20
www.arjuna.com

----- Original Message -----=20
From: Furniss, Peter=20
To: Mark Little ; malik saheb ; ws-caf@lists.oasis-open.org=20
Sent: Thursday, February 12, 2004 3:26 PM
Subject: RE: [ws-caf] Agenda for the demo application


Mark,

I've had a look and I still don't see a clear added-value of WS-Context
itself, or statement of what is deficient in using headers directly.
There are assertions, as in your first paragraph that WS-Context could
be used for various things, but I don't see what features it adds that
aren't there already or which have to be specified in some other
document known to the various parties.


The problem is that the additional specification (it is not necessarily
an ALS, it may just be specification - the GAF proposal is an example of
the sort of thing) has to define the interpretation and purpose of the
attributes and elements in the context. You could write virtually the
same specification text saying "this value is put in a SOAP header with
top-element qname" instead of "this value is put in a context with type
uri".

That would certainly seem to be the case for pass-by-bulk.
Pass-by-reference, once it's sorted out, comes down to the
general-purpose semantics of "here is a soap header with an element that
is a URI that can be dereferenced to give you more information."
Everything else is left to the addtional specification.

Undoubtedly the various specs that have context-like behaviour *could*
function with WS-Context, but I don't see what they would gain other
than "namespace paint" .


Peter

-----Original Message-----
From: Mark Little [mailto:mark.little@arjuna.com]=20
Sent: 12 February 2004 14:16
To: Furniss, Peter; malik saheb; ws-caf@lists.oasis-open.org
Subject: Re: [ws-caf] Agenda for the demo application


Peter, I think you missed the point. I realise you weren't at the first
face-to-face, (and I've no idea if you'll be at the next one where I'm
sure the demo app will be described), but this kind of discussion came
up in Boston. It was also one of the original FAQ questions (can't say
for sure if it's on the current TC FAQ though). One of the intentions of
WS-Context is to try to provide a standard way of approaching context,
rather than the ad hoc mechanisms that currently exist. For example, it
would be great if WS-Security adopted WS-Context, for example; though
whether that actually happens is a different issue entirely. WS-RF as
another example may be able to utilise WS-Context.

An aim would be to provide a standard that allows existing and new uses
of context to be more easily created and to work collectively. I find it
strange to be going back over what the aims of this TC is, since we're
4+ (?) months into it, but: we'll define a standard context
representation that all users will agree upon and can augment if
required; the location of context will also be precisely defined such
that it is no longer a hit-and-miss thing to be able to identify
pertinent "context" information in a header or body. I don't think this
is a waste of time and effort, and just looking outside of this TC
neither do the various companies that we have talked to.

And with regard to my comments on the demo. application: as I said, I
can see how context could be used in the way currently described, I just
think that an alternative approach may well be easier to describe and
understand.

Oh, and WS-Context can be used entirely by itself, i.e., without any
ALS-es. It was designed to. Check out
http://www.arjuna.com/library/reports/2003-08-12-GAF-v1_0.pdf for
example.

All the best,

Mark.

P.S. If we're going to discuss the demo. specifically then let's take it
to the separate working group.

----
Mark Little,
Chief Architect, Transactions,
Arjuna Technologies Ltd.
=20
www.arjuna.com

----- Original Message -----=20
From: Furniss, Peter=20
To: Mark Little ; malik saheb ; ws-caf@lists.oasis-open.org=20
Sent: Thursday, February 12, 2004 1:46 PM
Subject: RE: [ws-caf] Agenda for the demo application


WS-CAFites,

The proposed demo application, and Mark's comments on it are very
interesting as showing two different approaches by the author companies
(who are to be congratulated on having such discussions in the open,
rather than huddling away in a corner :-). But they raise a query I've
had in my mind about WS-Context.

By design WS-Context can't be used completely alone - there has to be
some additional specification known to the various parties - so in the
demo application, the client and the retailers all know of the shopping
cart application. Exactly what behaviour is required of them differs
slightly between the demo as written and Mark's suggestions - but the
client has at least to know that it has to put the context on the
messages to the retailers, and the retailers to know they must make
their supplying part of the cart.

The problem I have is that I can't quite work out what WS-Context adds
that isn't already available in SOAP headers. The WS-Context-using
shopping cart specification will be identified by a URI (the "type" in
the context -this is probably the same as, or related to, the
ALS-context identifier). A service receiving a context with that uri (or
finding it after dereferencing a pass-by-reference context) will thus
know what it has to do, as specified by the shopping cart spec: but
that's all part of the shopping cart spec, and not WS-Context
(especially if, as Mark suggests the shopping cart ALS offers its own
service, with addToCart, removeFromCart).

Compare that with exactly the same shopping cart service specified using
SOAP header, and able to generate a unique shopping cart identifier. The
shopping cart specification defines a soap header, using the namespace
uri to identify it's headers among all the other that exist. The header
includes the URI of the shopping cart service and any other identifiers
- in fact exactly the same information that it would need to specify as
being contained in the context had it used WS-Context. A service
receiving a shopping cart header does exactly the same things as one
receiving a shopping cart context.

The demo app as described does have the Context Service doing more, but
that seems to be what can be done with http anyway - the context
identification URI labels a resource that can be fetched (get) or
changed (put) (but no equivalent of post at ctx level).

The shopping-cart service is using the Context-service to generate the
unique identifier, but that isn't difficult to do itself (and might well
be counter-productive to take one in from the Ctx service, since if the
shopping cart chose its own URI's it could put locally-meaningful (but
externally opaque) information in them, whereas if the URI is given to
it by a Context Service the cart service must indirect through a hash or
whatever.)

To summarise:

What gain does a WS-Context-using specification gain from WS-Context
that it could not have got from the combination of:
=20
    - SOAP Headers, which identify, by the namespace URI which
specification they refer to and can contain elements and attributes of
use to that specification

    - HTTP Get, Put and Post which can fetch, set and modify a
remotely-held body of information unambiguously identified by a URI

Good grief, I've turned into a RESTafarian ! =20
 =20

This isn't to say there might not be something in the higher levels of
WS-CAF (I have thoughts on that too :-), but I have a suspicion that by
the time you've generalised the context-layer sufficiently to make it
general (i.e. to justify ws-context as a separate spec), there isn't
anything left worth specifying. Yes, several things need to pass around
identifications, and associated information and there are some protocol
design issues that are worthy of summarising (e.g. rules about
unambiguity must be precise, implications of id exchange) but there
isn't anything worth making into a distinct protocol.

Peter

------------------------------------------
Peter Furniss
Chief Scientist, Choreology Ltd
web: http://www.choreology.com
email: peter.furniss@choreology.com
phone: +44 870 739 0066
mobile: +44 7951 536168


-----Original Message-----
From: Mark Little [mailto:mark.little@arjuna.com]=20
Sent: 11 February 2004 11:53
To: malik saheb; ws-caf@lists.oasis-open.org
Subject: Re: [ws-caf] Agenda for the demo application


I've attached comments to the document. As far as I can see, this still
needs work. The architecture of the application seems to be a very
strange use of context in general, and WS-Context specifically. Maybe
this is a carry-over from the WS-I demo?

Mark.

----
Mark Little,
Chief Architect, Transactions,
Arjuna Technologies Ltd.
=20
www.arjuna.com

----- Original Message -----=20
From: malik saheb=20
To: ws-caf@lists.oasis-open.org=20
Sent: Monday, February 09, 2004 7:00 PM
Subject: [ws-caf] Agenda for the demo application


Hi All
=20
I have attached the document explaining how the demo application can use
the WS-Context.=20
The way the demo will use the other specifications will be provided
later according to the schedule described below and that follow the
following steps.
=20
- Before a meeting we will produce a document describing the demo
application using a particular specification (deadline 1 week before the
meeting)
- During a meeting the document made previously available will be
discussed=20
- Show a demo application with a particular specification (no demo for
the Paris meeting)=20
=20
In other words:
2nd meeting - Paris
- Before the meeting - we provide the demo application with the WS-CTX.
- During the meeting - Discuss the demo application with WS-CTX=20
=20
3rd meeting New Orleans=20
- Before the meeting - produce a document of the demo application with
WS-CF
- Discuss of the application with WS-CF=20
- Show the Demo Application with the WS-Context (described in the
previous meeting)
=20
4th F2F meeting (date to be determined) -=20
- Before the meeting - produce a document of the demo application with
WS-TXM
- Discuss of the application with WS-TXM
- Show the Demo Application with the WS-CF (described in the previous
meeting)
=20
5th F2F meeting (date to be determined) -=20
- Show the Demo Application with the WS-TXM (described in the previous
meeting)
=20
Malik=20
=20