A Task Management Model in CSCW Liao ChunYuan, Shi YuanChun, Xu GuangYou Dept. Of Computer Science, TsingHua University, Beijing, P.R.China,100084 e-mail: [email protected]

Abstract Cooperation Management is one of the most important subjects of the researches on CSCW, which intends to mediate the cooperative relations between workgroup members in the integrated CSCW supporting system, but not to focus on how to implement the single cooperative work itself. Getting inside view of the cooperation process, we are convinced that there exist mainly three cooperative relations in the process, which are hierarchy relation、constraint relation and temporal relation. To describe and manage the cooperative relations effectively, we purpose here a concept of “Task

“Activity”

to

represent

cooperative

work,

and

employs

Object-Oriented method to implement required functions by the Integrated CSCW supporting system, such as activity design, wokflow specification, actor assignment. A shortage of these systems lies in too much attention paid to the implementation of the separated single activity or work, with the lack of deep analysis and comprehensive maintenance of the cooperative relations between related activities, which may be, in fact, the most important aspect to be accounted for to achieve a integrated CSCW supporting system.

Management ” ( TM ) and its model, TAMM( Task—Activity

Therefore, we propose here the concept of “TAMM”, modeling

Management Modal), followed by a prototypical system based on

the cooperative process, both synchronous and asynchronous

them. In this paper, we begin with the introduction of some existing

cooperation, as a series of “Activities”, and describe the cooperative

models and systems, next depict the three relations, with the concept

relations between workgroup members as the ones among

of TM and TAMM, then give an overview of our prototype system

“Activities”.

and the summary at last.

which mostly fall into tree categories here hierarchy relation,

To establish and maintain the cooperative relations

constraint relation and temporal relation, we also introduce another concept of “Task Management”. In this way, we can represent nearly

Key words: Integrated CSCW supporting System, Task Management, Task—Activity Management Model, Hierarchy relation, Constraint relation, Temporal relation

all the practical cooperation in one uniform framework, including Task Assignment, Workflow, Data constraint and so on. This paper is organized into the following sections: First, we give a overview on some existing CSCW supporting systems, next analyze the practical cooperation process, present our model of “TAMM”, then address the three import cooperative relations in the

1.Introduction 1990s see the rapid improvement of the research on CSCW, but the developed CSCW systems so far mainly focus on more or less a narrow subfield of cooperative work, such as workflow system, video conference, white board, or joint authoring and so forth. As the

Integrated CSCW supporting System and the concept of “Task Management”, followed by an prototypical realization and the summary at the end.

2.Existing systems

result of this, users sometimes must exploit several different

As Teege says, the CSCW supporting system usually fall into

applications simultaneously to accomplish a single cooperative work,

three groups as follows: The first group includes specialized systems

with weak interoperation between them. And thus, the need of the

supporting only one or a few specific aspect of cooperative work.

integrated CSCW system seems obvious [1].

The second includes systems upholding activities, and the last

Many works have been done on the research of the Integrated

includes Integrated CSCW supporting Systems[1].

CSCW System, among which are early Oval, Linkworks, EuroCoOp

Among those application systems, what we see and use usually

projects, and recent OOActSM and so on. Pippa Hennesy[2]

belongs to group one or two. As an example, we first introduce an

addresses a prototype system based on the concept of “Task” and

Internet-based Workflow system[3], which extends the basic desktop

“Task Context”, which views the Task and Task Context as different

environment to an Internet-based one and provide users with the

aspects of the set of information about a cooperative process, and

support of the dynamically reconfigurable desktop and workflow

provides users with some toolkit applications supporting task

specification. Another example is presented as Collaborative

assignment, synchronous and asynchronous communication, message

Workspaces for Time Deferred Electronic Cooperation[4]. With

handling and so forth. While Gunnar Teege[1] proposes a model of

equal access of the participants to the objects of the cooperative work

as required for team-like cooperation, the system facilitates an

providing solutions of typical CSCW problems. It gives a definition

weakly structured cooperation processes with implicit coordination.

of the “Activity” as a structured entity with a “Activity Context”,

As stated previously, these system are engaged in upholding only

executed by an actor. As sated previously, OOActSM takes nearly all

some subfields of CSCW, lack of comprehensive and flexible support

aspects in the cooperative work as objects, such as Activity, Context,

for cooperative work, thus can be only used in some specialized

synchronous/asynchronous communication, even the connection

areas.

among them. Furthermore the Activity specification corresponds to Many Integrated CSCW supporting systems, belonging to the

group three, originate from the concept of “Activity” or “Task”, among which the EuroCoOp and the OOActSM are typical examples. They will be depicted later in greater detail than the former two systems known as “Task-Activity Management Model”, which bear some similarities to our model,. EuroCoOp

project[2],

selecting and setting of the specific class as super classes like traditional OO method. With a extended scheme of multiple inheritance, Gunnar Teege implements a integrated CSCW supporting system by selecting different objects representing distinct aspect of cooperation and combining them to yield a new class, which can accomplish multiple functions in a single object instance. Like EACM, what OOActSM is concerned with is not the

conducted

by

several

European

universities and firms, aims to develop a generic system for supporting distributed cooperation through integrating components from existing systems and opening up some new tools. EuroCoOp addresses an task-oriented model, namely EACM ( EuroCoOp Activity Coordination Model ), which is based on the concept of “Task”, defined as the set of details describing the planned and actual

maintenance of the cooperative relations, instead the concrete accomplishment of each activity. As a consequence, we argue that an Integrated CSCW supporting system should provide support, except for what is realized by the previous systems such as communication, workflow specification, actor assignment et., as follows:

performance of some real-life task, and the concept of “Task

•Explicit establishment and maintenance of cooperative relations,

Context”, defined as the set of the information relevant to the

which appear an relatively independent module in the Integrated

performance of a task. A Task consists of some property fields,

CSCW supporting system so as to make its architecture more rational

among which are actor, deadline, starting date, duration, starting

and more clear.

condition, end condition, status and so forth. By this means, the work

•Modeling main aspects involved in cooperative work in an uniform

process can be planned and recorded in the course of its performance. While a Task Context maybe have attributes such as title, description,

•Giving a principle for the construction of the structured cooperation,

subtask and participant list. Both “Task” and “Task Context”

framework.

are structured, that’s to say,

there exist hierarchy relations between the subtask/subtask context

such as how to organize the task or how to separate a task into several subtasks

and super task/super task context in the EACM. But the principle of

•Definition of dependency among the data related to the coordination,

how to construct the structure of the specific task, the process of task

which indicates an important collaborative aspect in the cooperation.

assignment, is not explicitly indicated, as well as the important

Driven by this aim, we propose the concept of “Task

concept of hierarchy relation in cooperative work. On the other hand,

Management” to achieve comprehensive support for the cooperative

EACM also support the workflow specification by means of

work, based on the model “TAMM” which depicts the activities and

specifying the involved task’s starting condition and/or end

their connections in the operation process. To depict the scheme

condition[2]. But EACM doesn’t directly uphold the definition of the

logically, we will give an inside view of the cooperation process as

dependency among the data associated with the cooperative work,

following at first.

which is very useful in the case of joint authoring and joint design. As a whole, EuroCoOp concentrates mainly on implementation of

3.Task-Activity Management Model

the plan, monitoring, recording of the working process, and try to provide flexible and powerful communication method between workgroup members. But it is lack of strong support for the mediation of the cooperative work, the maintenance of the cooperative relations, which is considered by us as one of the primary functions of the CSCW supporting system.

According to the time when the concrete operation is performed by participant, we can generally classify the cooperative works into two categories as synchronous cooperation and asynchronous cooperation[5]. Usually, an asynchronous cooperation, which consists of several tasks executed by different worker at different point in time, is accomplished step by step, and each step

The same hold true in the OOActSM ( Object-Oriented

has certain actor, relevant data, content of manipulation and so on.

Activity Support Model )[1], proposed by Gunnar Teege as a model

For example, in the course of preparation for a meeting, we should

for integrated CSCW supporting system. The distinct character of the

fix the subject and determine the participants first, next schedule the

OOActSM is the usage of the object-oriented mechanism for

meeting, then hold the conference, followed by producing and

•Ending Condition

distributing of a formal protocol. Each of those steps contains certain

•Starting Time, at this point the Activity must be activated and goes

information about order, aim, operator and associated material. So does the synchronous operation. As a typical example of this, we can

on work.

get a view on the video conference, where the chairman begins with

•Deadline, the limit of time before which the activity must be

declaration of the conference‘s theme and target, next passes the

completed.

control to the other participants in turn to conduct the discussion, at

•Super Task, from which the activity is derived. As respect to Task,

last summarizes and draws a conclusion. In one word, the

the greater detail will be addressed below.

cooperation process is made up of individual steps, or subworks, with certain information about the execution of cooperative work.

Activity entity corresponds to the leaf node in the hierarchic tree of task assignment. While we also give the definition of the “Task”, as

On the other hand, a cooperative project can be organized into

“work with some subworks, which is abstract, and only contributes to

several hierarchic subworks in respect of the task assignment. In fact,

organization of the whole cooperative process instead of specifying

we generally refine the whole project roughly into several goals,

the concrete operation to conduct individuals”. Like Activity, a Task

which can be viewed as a collection of some smaller goals or tasks in

has also some property entries, which are followed:

the same way as before. Repeating the procedure, we finally get a hierarchic tree of task arrangement, where the inner nodes represent

•Super Task, from which the task is obtained. That is to say, the

some roughly organized tasks without certain assignment of actor,

super task can be organized into several subtasks, among them is this

relevant data, manipulation and so on, while the leaves nodes contain

task.

the concrete task plan so as to conduct the certain operation. For

•Description, outlining the task about its subtasks and general aim.

instance, in the scheme of a joint authoring with multimedia technology, first we can generally separate the whole project into following parts: painting, composition, collecting original audio and video material, programming, each of which corresponds to a inner nodes in the tree of task assignment and is used just for an easier

As stated above, a Task entity has much less attributes than an Activity entity, since being employed just for easier organization of the cooperative work rather than for representation of a certain operation.

organization rather than conducting the specific actor to do concrete

Based on the concept of “Activity” and “Task”, we propose the

work. In contrast to this, the refined subtask of them may give the

model “Task-Activity Management Model”. Through this model, we

participants specific information to start task. As an example, we can

can take the procedure of the Task Assignment as the process of

refine task “Composition” further into “authoring for section 1,

constructing a structured organizational tree, where the root node,

executed by Bill with the title ‘Abstract’ ” and “authoring for section

modeled by a Task, indicates the whole cooperative project, and its

2 which is assigned to Tom with title ‘Introduction’ and some

children nodes denote a Task or an Activity. In the case of Task, the

description of his work”. By this means, Bill and Tom can begin their

children nodes can be made fall into several more fixed and certain

task right now, with the conduction of the refined scheme.

subtasks or Activities. On the other hand, the an Activity node

Thus, we are convinced that every cooperative process can be viewed essentially as a collection of subworks with certain information to conduct participants’ performance, ether in the aspect of execution or of planning. Based on this, we propose the concept of “Activity” as “A concrete work without more refinement, which represents a specific operation process executed by one or a group of actors in a project”. An Activity consists of a serial of attributes as follows: •Actor, assigning the worker, one or more, to perform the Activity.

needn’t be refined any more, because of its adequate information to conduct the coordination. The principle of constructing the structured tree will be given below, which is one of the main ideas in this paper. At the same time, we also cast the execution of the cooperation as one or more sequences in parallel containing multiple Activities with some process specific cooperative relation between them.

4. Relations in cooperation process and Task Management By means of Activity and Task, we can describe a cooperative

•Manipulation Type, indicating what operation to be executed.

work as a collection of Activities and Tasks. But it is establishment

•Relevant Data, containing the information of the work’s material,

and maintenance of the connection among them that we are mostly

such as path of the referenced files and destination file, text format

concerned with, rather than the implementation of the Activities /

and description of main content.

Tasks themselves. In fact, getting an inside view of the cooperation

•Starting Condition, describing the condition under which the Activity can/must be performed.

process, we are convinced that there exist mainly three kinds of cooperative relations in a collaborative project, known as hierarchy relation, constraint relation and temporal relation, of which the

description and analysis are following:

which denote an kind of work-specific semantic information.. Paul Dourish also describes an constraint relation in their

4.1 Hierarchy Relation

workflow system model, Freeflow[6], which bears some similarities to ours. He believes that there exist two relationships between tasks

This kind of connection lies between Activities/Tasks and their super Task, originating from the assignment of the cooperative work. And as a result, we obtain a structured, multi-level tree of work assignment. Now, our concern is with how to organize a given Task and what extent the procedure of refining Task will be proceeded to.

in a workflow system—a temporal relationship concerning the ordering of activities, and a dependency relationship indicating a continuous connection between task’s states. For example, you can define a dependency as “A must be completed before starting B”, or ”the value of A is constrained to be twice the one of B”. As

We argue that, a Task should be organized according to the classes of

described above, the Freemodel confuses the dependency of

either involved manipulation or relevant data of the potential

executing order with that of task’s content. And thus, we restrict the

subtasks / Activities. For instance, against the classes of manipulation,

dependency relation of Activity to that of the data of Activity, and

we can refine the joint authoring with multimedia as before into four

represent the temporal dependency as follows:

subtasks: Painting, Composition, Gleaning multimedia data and Programming, each of which involves different operation from others. For the lack of the sufficient information to go on concrete work, the

4.3 Temporal Relation

Task “Composition”, for a example, should be separated further into

Temporal relations normally lie among Activities in a specific

some Activities, such as Activities of “Bill write section 1 titled

workflow. We can classify the temporal dependency of Activities into

“Abstract””, ”Tom write section 2 titled “Introduction””. This is done

two categories:

according to the different relevant data involved in the Task

•Manipulating Activity at absolute time

“Composition”. It’s import to note that only one aspect once, either operation or data, could be adopted to classify the potential subtasks or Activities whenever refining a given Task. Otherwise, it might lead to unnecessary confusion. As an example, it is more rational and logical to organize the Task “Composition” into subtasks as “writing”,

In this case, the concerned Activities share a common time dimension, and start or stop at the prescribed point in time, controlled by a calendar. For example, you can define dependency as “A must be accomplished before 7pm and B must start at 3 am”. •Manipulating Activity at relative time

“revise”, ”edit”, among which “writing” can be refined furthermore

With this relative relation in time, the start-up or deactivation

as Activities: “Bill write section 1 titled “Abstract””, ”Tom write

of specific Activity is subject to the performance of other specified

section 2 titled “Introduction”, than to separated the same Task into

Activities, and nobody knows when to start or stop an Activity at the

four

titled

point to describe the temporal relation. For instance, definition of “A

“Abstract””, ”Tom write section 2 titled “Introduction”, “revise”,

must be achieved before B’s start-up” show only the relative time

“edit”.

rather than the absolute time as category one.

subtasks/Activities:

“Bill

write

section

1

On the other hand, it’s very difficult to regulate in quantity the

Definition and maintenance of temporal relation are similar to

extent to which a Task should be refined. In general, the proceeding

the traditional workflow mechanism, which engaged in organizing

of refinement could be believed completed as soon as the project

the assigned chaotic Activities into some structured sequences of

administrator can assign the certain value to all the attribute fields of

work and guiding the users to achieve the whole goal step by step.

an Activity as described in section 3. Of course, this depends mainly

Through this, it is possible to decrease the fault and delay so as to

on the administrator himself.

improve the efficiency of working. Thus, the workflow system, supporting temporal relation, may be the most prevalent application

4.2 Constraint Relation

in field of CSCW, on which more researches have been conducted than any others.

Constraint relations present among the Activities whose related data is restricted by each other in some senses. For instance, in case of CAD, an Activity is engaged in developing a new kind of axle, meanwhile another Activity in designating corresponding gear, where the designed axle’s diameter and the gear’s aperture must correspond with each other. As we know, the specification of workflow describes the temporal dependency between the Activities, while definition of constraint relation depicts the dependency of viscera among them

Following the description of the three cooperative relations, we propose the concept of “Task Management” as “the definition and maintenance mechanism of the cooperation relations in the Integrated CSCW supporting system”, which is employed as a relatively independent module in the system and devoted to establishing and maintaining those important cooperative relations in collaborative work process.

5. A prototype system

from Activity1 and the one of “Started” from Activity2. By this

Combining the TAMM with the analysis of cooperative relations, we have implemented a prototypical Task Management

means, it’s possible for users to describe and achieve more complex workflow easily.

Module as a part of the Integrated CSCW supporting system, which

As far as the scheme of concrete implementation, we have

provides the support for the construction of hierarchic mission

employed CORBA distributed objects technology and Java as the

assignment, definition and maintenance mechanism for data

programming language, which is thought the best solution to achieve

constraint, specification of workflow and so forth in one uniform

distributed, object-oriented, heterogeneous systems[7][8].

framework.

6.Summary

The establishment of the hierarchy relation between Tasks and

In this paper, I have defined the model of Task–Activity

Activities lie in the process of constructing mission assignment tree.

Management Model and give the concept of Task Management, with

With visual user interface, you can select a Task/Activity node, and

the analysis of the cooperative relations in collaborative working

edit its attribute or add some new subtasks/Activities( in case of Task

process.

node ) as children nodes. Of course, you can also delete a specific Task or Activity node if have the corresponding permission. As the result of this, you finally get a hierarchic mission assignment tree, which contain all necessary information about the organization, schedule, right and obligation of individual etc.

Every cooperative process, with regardless of synchronous or asynchronous cooperation, consists of a group of “Activities”, and for easier organization, we also introduce the concept of “Task”. Among the Activities and Tasks, there mostly lie three kinds of cooperative relations, known as hierarchy relation, constraint relation

The constraint relation is represented as a “Link” from an

and temporal relation, whose establishment and maintenance are

“Source Activity” entity to another “Destination Activity” entity

believed one of the most important considerations in an Integrated

concerned with the relevant data of the former. And when some

CSCW

changes are made to the concerned data, a prescribed message with

Management” is proposed to devote to definition and maintenance of

some comment will be sent to the “Destination Activity”, which will

these relations, as a relatively independent module in the whole

be triggered and notify its actor to resort to corresponding solution.

system.

In the future, the message should be responded automatically by the supporting system, in order to achieve automate maintenance of dependency for Activities.

supporting

system.

Therefore,

the

concept

“Task

Based on this, we have implemented a prototypical system exploiting CORBA technology and Java as programming language, where the establishment and maintenance of the hierarchy relation is

By a calendar mechanism, we achieve to maintain the absolute

combined into the mission assignment, while that of the constraint

temporal relation easily. While, the specification of workflow,

relation and the temporal relation are achieved by the triggering of

support to the temporal relation, is facilitated through the conditional

the involved Activities with “Link” and logic expressions. So, We

triggering of the Activities. That is to say, the workflow administrator

can describe and maintain the cooperative relations in one uniform

can prescribe a series of “signals” attached to an Activity during the

framework, and provide a comprehensive support for the

definition of it, each of which contains following attributes:

Cooperation Management.

•Sending condition, under which the “signal” will be sent to the specific Activities. •Type, depicting the semantic of the signal, such as “Started”, “Ended”, “Active”.

[1] Gunnar Teege, Object-Oriented Activity Support: A Model for Integrated CSCW Systems, Computer Supported Cooperative Work: The Journal of Collaborative Computing 5, pp.93-124, 1996

•Destination Activities, which will receive the signal once the sending condition is satisfied.

[2] Pippa Hennessy, et al, Distributed work management: activity coordination

•Context, containing all the relevant information, such as comment, related data.

within

the

EuroCoOp

project,

Computer

Communication, Vol 15. No 8. Oct.1992, pp.477-488, 1992 [3] Hemang Lavana,Internet-based Workflows: A Paradigm for

At the same point in time, each Activity is assigned two logic expressions for Starting Condition and Ending Condition as stated in section 3.As a example of this, you can define a logic expression for Starting Condition as “ SigalOfActivity1.Type = Stoped AND SingalOfActivity2.Type

Reference

=

Started

”, meaning this Activity

will be triggered and start as soon as receiving the signal of “Stoped”

Dynamically Reconfigurable Desktop Environments. In proceedings of the Group 97 Phoenix Arizona USA, May 1997 [4] Uta Pankoke-Babatz, Collaborative Workspaces for Time deffered Electronic Cooperation. In proceedings of the Group 97 Phoenix Arizona USA, May 1997 [5] Pei YunZhang, Research on Cooperative Working Environment:

Thesis of master degree, TsingHua University, BeiJing, China

June

1998 [6] Paul Dourish, Freeflow: Mediation between representation and action of workflow system, In proceedings of the CSCW’96 Cambridge MA USA, 1996 [7] Rober Orfali, Client/Server programming with Java and CORBa, Wiley Computer Publishing, USA, 1997

[8] Visigenic Programmer’s Guide, Inprise Cooperation, 1998