BPEL4People规范阅读笔记--赵翔鹏的Blog

BPEL4People规范阅读笔记
翔发表于 2007-7-8 17:44:00

下面是我前几天读WS-HumanTask和WS-BPEL4People规范时作的笔记，因为有太多术语，所以就直接用英文写了。不保证笔记的完全正确性，只是用于日后参考。
关于bpel4people的更多资料，请参考http://del.icio.us/tags/bpel4people上搜集的各个页面。

RBAC related basic concepts (Sec. 3, WS-HumanTask):

organization entity (a person or a group of persons. Must be linked to outer RBAC/LDAP user database)

logical group (roles of the process, i.e. "voters", "approvers". Must be linked to outer RBAC/LDAP user database)

generic roles (task initiator, stakeholder, potential owner, excluded owner, admin, notification receipient)

process initiator/stakeholder/admin are defined in BPEL4People spec.
person assignments (use an expression (literal, logical group, etc.) to assign some people to some generic role)
e.g. we can assign logical group "voters" as the potential owner of task "vote", or assign the "previous approver" as the excluded owner of task "approve_2")
In other words, we can define the potential owners of a task dynamically; thus we can do SoD and BoD.)

From a task's view: (Sec. 4, WS-HumanTask)

* A task includes (page 23-36):

service signature (input/output parameter, operation name, etc)
people assignments, indicating who can do the task, and who cannot, etc.

When a task is executed, it will have an "actual owner".

deadline requirements

two kinds of deadline: start/complete
can define multiple deadlines on different times with different behaviors
If timeout, then calculate each escalation's condition, and execute the corresponding behavior (behavior can only be either notification or reassign)
e.g. 1 hours after start -> notify manager, 2 days after start -> notify director, 1 day after complete -> reassign task owner

delegation requirement (to whom can we delegate the task? nobody/anybody/...)
attachment requirement, priority, comment, represetation info., etc.

* A task's lifeline (page 37-38):

created (by business process)
ready (created, but no one claims it yet)
researved (some potential owner claims it) [Note: delegate, revoke(release) can be done in this state]
inprogress (some one starts it) [Note: revoke, stop, delegate can be done in this state]
completed
failed (divide by zero, or the performer thinks it is a bad task)
obsolete (owner skips it, e.g. the receiver discards a notification, or gives up the right to vote)
terminated (outer scope terminates, or timeout)
a task can also be suspended and resumed (I'm not clear about this yet)

* Notification (Sec. 5, WS-HumanTask)

is a one-way, asynchronous human task
can only assign "receipients" to a notification, rather than "potential owners"

From a user's view (page 42-54):

* Normal User

claim, start, release, complete, fail, delegate ... a task

use "remove" for notifications

query tasks (similar to a SQL select. can specify many parameters, e.g. "Task.Priority=1 AND maxTasks=10")

* Administrator

activate (set status to Ready)
nominate (set potential owner to a specific person, and set task status to
set role (change people assignment dynamically)

From business process's view: (WS-BPEL4People)

* A process includes:

some logical group definition (roles in the process, i.e. "voters", "approvers". Must be linked to outer RBAC/LDAP user database)
person assignments of process generic roles (process initiator, process admin, etc.)
human task definitions
process definition, where each "human task" is wrapped in a "people activity", whose syntax follows the spec of BPEL.

task definitions can be given inside a people activity, at the beginning of the process, or elsewhere. (see "constellations" on page 16)
a globally defined task's people assignment or priority can be overidden in local people activity.
people activity's state diagram is at page 27. (running, completed, obsolete, failed, terminated, closed)

First Impressions

* The idea

Task owners can be specified in a fine-grained way in the task definition, and can change dynamically.
Many states for a task, many possible operations for a user (which states/operations are important, which are not?)
Fine-grained deadline support

to read: what if several escalation conditions have overlap?

Two spec instead of one

aims at the separation of TaskEngine, TaskList, BPEngine, so that we can combine different products together (see the official podcast)

Question: how to link logical group to actual users? Can this link be changed dynamically by process admin?

* The spec text

Quite long, but quite easy to read (compared with the BPEL spec)
Read the examples for a quick start!!! (The final sections of the specifications)
Still some small errors in the spec

e.g. page 54 has a typo "assigment".
In the task state transition figure, the word "revoke" is used. However it is called "release" in the text.

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Re:BPEL4People规范阅读笔记
sleepwindbell(游客)发表评论于2007-8-23 11:17:00

能不能介绍一下这些基本规范之间的关系，如BPEL4People
，WS-HumanTask和ws-BPEL2.它们是怎样协同工作的。因为规范太多，感觉很乱。谢谢

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