RE: [wsdm] [mows] WS endpoint definition

["Sedukhin, Igor S" <Igor.Sedukhin@ca.com>]

Title: Message

Here is a shortened definition of an endpoint

 

"An endpoint is an addressable location at which a Web Service can be accessed according to the associated binding of a specified interface. One Web Service can have multiple endpoints. In simple terms it is a network location identified by a URI which accepts XML requests to a service. XML requests must be formed according to WSDL description.

 

In OGSI, a Grid Service has endpoints and a Grid Service Instance has endpoints. Both can be described in WSDL."

 

 

-- Igor Sedukhin .. (igor.sedukhin@ca.com)
-- (631) 342-4325 .. 1 CA Plaza, Islandia, NY 11788

-----Original Message-----
From: Sedukhin, Igor S
Sent: Thursday, August 07, 2003 9:13 PM
To: wsdm@lists.oasis-open.org
Subject: [wsdm] [mows] WS endpoint definition

Fulfilling my AI from last MOWS call.

I propose that we stick to the definition given in WSDL 1.2 draft. In my opinion it is quite precise.

WSDL describes Web services starting with the messages that are exchanged between the service provider and requester. The messages themselves are described abstractly and then bound to a concrete network protocol and message format. A message consists of a collection of typed data items. An exchange of messages between the service provider and requester is described as an operation.

A collection of operations is called an interface. An interface is bound to a concrete protocol and message format via one or more bindings. A binding, and therefore an interface, is accessible via one or more endpoint, each endpoint having its own URI. A service is a collection of endpoints bound to the same interface.

Again, in simple terms it is a "place" identified with a URI where XML (or SOAP if some prefer) requests could be sent.

In case of OGSI, GridServices are WSs that could be described with plain WSDL (via flattening) and therefore accessible via endpoints as well. In case the "factory" approach is used to create "instances" of GridServices, each "instance" is essentially a service (even if it is temporary). The "instance" service has one or more endpoints where the requests could be sent. Therefore, each GridService "instance" endpoint is a WSDL endpoint. Such WSDL can be dynamically generated if so necessary, in fact, it appears inline in a Grid Service Reference. Now, these are my own practical conclusions on this, correct me if I'm wrong. So, (1) GridService has endpoints (2) GridServiceInstance has endpoints too.

I have seen the following text in the OGSI Primer which made me somewhat confused on the GridService itself. Technically, I'm pretty sure in the above stated, but logically there could have been some other intentions.

In OGSI-terms, a Grid Service is a general term referring to a template, a contract, an
interface described in GWSDL and the Grid Service Instances that must adhere to it. The
term Grid Service does not characterise a component that can be part of a Grid
application (i.e., it does not refer to a software component that can execute operations).
Instead, it is Grid Service Instances that are the logical recipients of operations.
In the OGSI world, a Grid Service Instance (GSI) has to be explicitly created (by a
factory or by the hosting environment) and then registered with a handle resolver.

-- Igor Sedukhin .. (igor.sedukhin@ca.com)
-- (631) 342-4325 .. 1 CA Plaza, Islandia, NY 11788