Re: choreographies implementation && access point

Dear Guadalupe,

I do not really have enough context to answer your question fully. I am 
not sure from what you have been reading so a url to a document from 
which you derived these questions would help.

Firstly WSCI (which was a working note into W3C and a precursor to the 
work of the Choreography Working group) is history only and so nothing 
of much value can be gleaned from it save the focus on a global model 
of peer to peer web service message exchange.

As to an access point I guess you could argue, from an observers point 
of view, that any form of interaction starts with one party wishing to 
achieve some sort of business goal (i.e. I wish to create a full 
itinerary including flight booking, hotel reservation, car hire and so 
on). So the access point would be from that user or participant. If you 
traced the choreography description across the myriad of web services 
involved then you would be able to trace (in lock-step) the actual 
exchange of messages between all the necessary web services and the see 
the same thing described in the choreography description. Thus a CDL 
would describe the observable message flow between the participants 
whilst completely preserving the peer-to-peer decoupled nature of the 
services and their interaction. A CDL is thus (at this level) a 
description of the external observable behaviour of some business goal 
(at least from the point of view of the entity that wishes to create 
their itinerary).

WSDL only described end points and does this as simple sets of types 
and methods.

Abstract WS-BPEL described a single party behavioural type, so it's a 
step up from WSDL because it has some notion of ordering across methods 
and types and so has some notion of what is valid behaviour for a given 
state. This helps for the simple cases (in particular within the 
firewall) but does little to help in the grander picture in which we 
have many peer-to-peer cross organisational services interacting.

The biggest obstacle to true interoperability across the web is in 
ensuring peer-to-peer cross organisational services interaction can 
take place. How better to do this than describing a multi-party, 
peer-to-peer observable behaviour model of interaction; which is what 
Web Service Choreography is all about.


Hope this helps to clarify.





On 17 Jan 2004, at 13:10, Guadalupe Ortiz wrote:

> I´m a bit confused in the way you can use a choreography once it has 
> been described with the XML interfaz.
> * Wich is the access point? Is it in the choreography WSCI, or in te 
> particular WSDL from the different services?
>
> * Once the choreography interface is describes, should we interpret it 
> or compile it; or should we create an aplication that shows the 
> behavier previously described.
>
> Thanks in advance
Best Regards

Steve Ross-Talbot
Chair W3C Web Services
co-Chair W3C Web Services Choreography

O: +44 207 397 8207
C: +44 7855 268 848
www.enigmatec.net

Received on Saturday, 17 January 2004 09:04:25 UTC