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Sent: Monday, January 19, 2009 01:05
To: Dave Ings
Subject: Re: [bpel4people] BPEL4People TC - 1Q09 F2F Final Agenda
Dear all,
Here is my issue proposal. This is just formalizing the phone
presentation I did in December.
Title: A need for a "GetUI" or "StartTask" request/message for a Task
Web Service
Raised By: Yoichi Takayama
Target:
WS-BPEL Extension for People (BPEL4People) Specification V 1.1, CD 02
(proposal), 6 Jan 2009, Section 6 (and related sections)
Also:
Web-Services Human Task (WS-HumanTask) Specification Version 1.1, CD
02 (proposal), 6 Jan 2009, Section 7 (and related sections)
document_id=30552
Description:
In WS-HumanTask Section 7, Figure 1, the requestMessage presumably
corresponds to createTask message of the Task Life Cycle management.
Although this causes to "Register" the WS-C protocol handler EPRs
between the Task Parent and the Task (implemented as a Web Service)
as the (2) and (3) indicate, the "requestMessage is an asynchronous
request and nothing follows after that. The (4a) is the asynchronous
return for the (1) requestMessage, as I understand it.
Presumably, following this step, there is the "start" message handled
by the Task Life Cycle management (BPEL4People 4.8 or WS-HumanTask
4.7), which presumably would get UI from the Task Implementation to
the Task Parent (and then to a Task Client and to its user agent that
the end human user uses to do the Task) and let the end user do the
human task. However, how this would be dealt with in an interoperable
manner is not shown by the specification.
Obviously, the (4a) or (4b) would not occur until the Task UI is
presented to the end user and some outcome has been produced. So, the
"start" step is a Task Service step that should be documented and
defined before the termination of the Task such as (4a) or (4b). This
is lacking in the specification.
We cannot presume that the Task Parent or the Task Coordinator knows
what operation or EPR to ask for to call it, since the specification
does not have any place that states such an operation or how to
specify such additional EPR for that operation, i.e. "StartTask".
Proposal:
1. Add a "StartTask" request message to Section 6.1 of the WS-
HumanTask and to the table of WS-C WS-HT messages (page 31). This
corresponds to the "start" Task Life Cycle management command, but is
distinct from it because it is one of the Task Web Service massages.
This may return either a single page UI (such as HTML Form or XML) or
an application UI (that could be a form of an EPR or URL or e.g. XUL-
application XML launch point). The Task may be an multiple-page Web
application or Desktop UI of an comprehensive application, for example.
2. For this reason, the interoperable format for the response message
of the "StartTask" must be defined so that it can be interpreted by
the Task Coordinator, Task Parent, and Task Client properly (so that
they will know what the response contains and what to do with the
information/data).
Alternative
We could provide an ability or a place to state the additional EPR
for StartTask, but that is tedious. If a fixed WS-C WS-HT message can
handle it, it is more consistent with the current CD and it may be
simpler.
Potential Problem
If a Web Service implements multiple Tasks with different EPRs, each
Task must implement different WS-C protocol handler and the
"StartTask" message handler with it. In this case, there may be more
efficient way to organize the whole WS-C WS-HT better.
Yoichi
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Yoichi Takayama, PhD
Senior Research Fellow
RAMP Project
MELCOE (Macquarie E-Learning Centre of Excellence)
MACQUARIE UNIVERSITY
Phone: +61 (0)2 9850 9073
Fax: +61 (0)2 9850 6527
www.mq.edu.au
www.melcoe.mq.edu.au/projects/RAMP/
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