NET-BASED TASK MANAGEMENT SYSTEMHector Garcia-Molina, Jeffrey D. Ullman, Jennifer WisdomABSTRACTIn net-based collaborative design environment, design resources become more and more varied and complex. Besides com mon in formatio n man ageme nt systems, desig n resources can be orga ni zed in connection with desig n activities.A set of activities and resources linked by logic relations can form a task. A task has at least one objective and can be broken down into smaller ones. So a design project can be separated in to many subtasks formi ng a hierarchical structure.Task Management System (TMS) is designed to break down these tasks and assig n certa in resources to its task no des. As a result of decompositi on. al1 desig n resources and activities could be man aged via this system.KEY WORDS : Collaborative Design, Task Management System (TMS), Task Decompositi on, In formati on Man ageme nt System1 IntroductionAlong with the rapid upgrade of request for adva need desig n methods, more and more desig n tool appeared to support new desig n methods and forms. Desig n in a web en vir onment with multi-part ners being invo Ived requires a more powerful and efficie nt man ageme ntsystem .Desig n part ners can be located everywhere over the n et with their own organizations. They could be mutually independent experts or teams of tens of employees. This article discussesa task man ageme nt system (TMS) which man ages desig n activities and resources by break ing dow n desig n objectives and re-orga nizing desig n resources in conn ecti on with the activities. Compari ng with com mon information management systems (IMS) like product data management system and docume nt man ageme nt system, TMS can man age the whole desig n process. It has two tiers which make it much more flexible in structure.The lower tier con sists of traditi onal com mon IMSS and the upper one fulfillslogic activity management through controlling a tree-like structure, allocating design resources andmaking decisions about how to carry out a design project. Its functioning paradigm varies in differe nt projects depending on the project ' s scale and purpose. As a result of this structure, TMS can separate its data model from its logic mode1.lt could bring about structure optimization and efficiency improvement, especially in a large scale project.2 Task Management in Net-Based Collaborative Design Environment 2.1 Evolution of the Design EnvironmentDuring a net-based collaborative design process, designers transform their working environment from a single PC desktop to LAN, and even extend to WAN. Each desig n part ner can be a sin gle expert or a comb in ati on of many teams of several subjects, even if they are far away from each other geographically. In the net-based collaborative desig n environment, people from every term inal of the net can excha nge their information interactively with each other and send data to authorized roles via their desig n tools. The Co Desig n Space is such an environment which provides a set of these tools to help desig n part ners com muni cate and obta in desig n in formatio n. Code sign Space aims at improving the efficiency of collaborative work, making en terprises in crease its sen sitivity to markets and optimize the con figurati on of resource.2.2 Management of Resources and Activities in Net-Based Collaborative EnvironmentThe expansion of design environment also caused a new problem of how to organize the resources and design activities in that environment. As the number of desig n part ners in creases, resources also in crease in direct proporti on. But relatio ns betwee n resources in crease in square ratio. To orga nize these resources and their relations needs an integrated management system which can recognize them and provide to desig ners in case of they are n eeded.One soluti on is to use special in formatio n man ageme nt system (IMS).A n IMS can provide database,file systems and in/out in terfaces to man age a give n resource. For example there are several IMS tools in Co Design Space such as Product Data Man ageme nt System, Docume nt Man ageme nt System and so on. These systemsca n provide its special information which design users want.But the structure of design activities is much more complicated than these IM S could man age, because eve n a simple desig n project may invo Ive differe nt desig n resources such asdocuments, drafts and equipments. Not only product data or documents, design activities also need the support of organizations in design processes. This article puts forward a new design system which attempts to integrate different resources into the related desig n activities. That is task man ageme nt system (TMS).3 Task Breakdown Model3.1 Basis of Task BreakdownWhen people set out to accomplish a project, they usually separate it into a seque nee of tasks and finish them one by one. Each desig n project can be regarded as an aggregate of activities, roles and data. Here we define a task as a set of activities and resources and also having at least one objective. Because large tasks can be separated into small ones, if we separate a project target into several lower—level objectives, we defi ne that the project is broke n dow n into subtasks and each objective maps to a subtask. Obviously if each subtask is accomplished, the project is surely finished. So TMS integrates design activities and resources through planning these tasks.Net-based collaborative design mostly aims at products development. Project man agers (PM) assig n subtasks to desig ners or desig n teams who may locate in other cities. The designers and teams execute their own tasks under the constraints which are defined by the PM and negotiated with each other via the collaborative design en vir onment. So the desig ners and teams are in depe ndent collaborative part ners and have in compact coupli ng relati on ships. They are drive n together only by theft desig n tasks. After the PM have finished decomposing the project, each designer or team leader who has bee n assig ned with a subtask become a low-class PM of his own task. And he can do the same thing as his PM done to him, re-breaking down and re-assig ning tasks.So we put forward two rules for Task Breakdown in a net-based environment, in compact coupli ng and object-drive n. In compact coupli ng mea ns the less relati on ship betwee n two tasks. Whe n two subtasks were coupled too tightly, the requireme nt for com muni cati on betwee n their desig ners will in crease a lot. Too much com muni cati on wil1 not only waste time and reduce efficiency, but also bring errors. It will become much more difficult to man age project process tha n usually in this situati on. On the other hand every task has its own objective. From the view point of PM of a superior task each subtask could be a black box and how to execute these subtasks is unknown. The PM concerns only the results and constraints of these subtasks, and may never concern what will happe n in side it.3.2 Task Breakdown MethodAccord ing to the above basis, a project can be separated into several subtasks. And whe n this separati ng con ti nu es, it will fin ally be decomposed into a task tree. Except the root of the tree is a project, all eaves and branches are subtasks. Since a design project can be separatedinto a task tree, all its resources can be added to it depe nding on their relati on ship. For example, a Small-Sized-Satellite.Desig n (3SD) project can be broke n dow n into two desig n objectives as Satellite Hardware. Design (SHD) and Satellite-Software-Exploit (SSE). And it also has two teams. Desig n team A and desig n team B which we regard as desig n resources. Whe n A is assig ned to SSE and B to SHD. We break dow n the project as show n in Fig 1.It is alike to man age other resources in a project in this way. So whe n we defi ne a collaborative design project ' s task m od e lshould first claim the project ' s targets These targets in clude fun cti onal goals, performa nee goals, and quality goals and so on. Then we could confirm how to execute this project. Next we can go on to break dow n it. The project can be separated into two or more subtasks since there are at least two part ners in a collaborative project. Either we could separate the project into stepwise tasks, which have time seque nee relati on ships in case of some more complex projects and the n break dow n the stepwise tasks accord ing to their phase-to-phase goals.There is also another trouble in executing a task breakdown. When a task is broke n into several subtasks; it is not merely “ a simple sum motioof other tasks. In most cases their subtasks could have more complex relati ons.To solve this problem we use constraints. There are time sequenee constraint (TSC) and logic constraint (LC). The time sequence constraint defines the time relati on ships among subtasks. The TSC has four differe nt types, FF, FS, SF and SS. F means finish and S presents start. If we say Tabb is FS and lag four days, it means Tb should start no later tha n four days after Ta is fini shed.The logic constraint is much more complicated. It defines logic relationship among multiple tasks.Here is give n an example:Task TA is separated into three subtasks, Ta, T b and Tc. But there are two more rules.Tb and Tc can not be executed until Ta is finished.Tb and Tc can not be executed both that means if Tb was executed, Tc should not be executed, and vice versa. This depe nds on the result of Ta.So we say Tb and Tc have a logic con stra int. After finishing break ing dow n the tasks, we can get a task tree as Fig, 2 illustrates.4 TMS Realization4.1 TMS StructureAccord ing to our discussi on about task tree model and task breakdow n basis, we can develop a Task Man ageme nt System (TMS) based on Co Desig n Space using Java Ian guage, JSP tech no logy and Microsoft SQL 2000. The task man ageme nt system ' s structure is shown in Fig. 3.TMS has four main modules namely Task Breakdown, Role Management, Statistics and Query and Data In tegrati on. The Task Breakdow n module helps users to work out task tree. Role Management module performs authentication and authorization of access control. Statistics and Query module is an extra tool for users to find more information about their task. The last Data Integration Module provides in/out in terface for TMS with its peripheral en vir onment.4.2 Key Points in System Realization4.2.1 Integration with Co Design SpaceCo Desig n Space is an in tegrated in formatio n man ageme nt system which stores, shares and processes desig n data and provides a series of tools to support users. These tools can share all information in the database because they have a universal DataModel. Which is defined in an XML (extensible Markup Language) file, and has a hierarchical structure. Based on this XML structure the TMS h data mode1 definition is orga ni zed as follow ing.<?xml version= 1.0 encoding= UTF-8' ?><!--comme nt:Com mon Resource Defin iti ons Above. The Followi ngare Task Desig n--><!ELEMENT ProductProcessResource(Prcses?, History? , AsBuiltProduct* , ItemsObj?, Changes?, ManufacturerParts?, SupplierParts?, AttachmentsObj?, Con tacts?, PartLibrary?, Additio nalAttributes*)><!ELEMENT Prcses (Prcs+) ><!ELEMENT Prcs (Prcses, PrcsNotes?, PrcsArc* , Con tacts?, AdditionalAttributes* , Attachments?)><!ELEM ENT PrcsArc EMPTY><!ELEMENT PrcsNotes(PrcsNote*)><!ELEMENT PrcsNote EMPTY>Notes: Element “Pros” a task node object, and “Processis a task set object which contains subtask objects and is bel ongs to a higher class task object. One task object can have no more than one “ Presseso b jects. According to this definition,“ Prcs o bjects are organized in a tree-formation process. The other objects are resources, such as task link object ( “ Presage ”sk notes ( “ ProNotes ”, )and task documents( “Attachments ” ) .These resources are shared in Co Design d atabase文章出处：计算机智能研究[J],47 卷，2007: 647-703基于网络的任务管理系统摘要在网络与设计协同化的环境下，设计资源变得越来越多样化和复杂化。