In This IssueSource: Operations Research, Vol. 36, No. 6 (Nov. - Dec., 1988), pp. 808-810+969Published by: INFORMSStable URL: http://www.jstor.org/stable/171113 .

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Tactical Logistics Planning have investigated how people address problem solving,

Many manufacturing firms are trying to lower the cost; little is known about how groups can use computer of delivered products to customers in order to protect support. One aspect being studied at the University of their market share and improve profitability. They are Arizona-in a test facility that includes networked shifting capital away from supporting growth and into PCs and a large wall screen-is how to improve group improving the productivity and efficiency of produc- meetings in a conference room using automated tools. tion and distribution facilities and equipment. For This is an important consideration because according some companies, this involves increasing the infor- to the Wall Street Journal (June 21, 1988), senior mation content in delivered products as a way to managers spend an average of 23 hours and middle displace more expensive resources. These firms rec- managers spend 11 hours a week in this activity. So, ognize that their success depends upon the ability PLEXSYS software was developed to help groups to manufacture a product economically and to communicate, define, generate, organize, evaluate and determine how much, when and where to make and select information electronically. One specific system deploy it. Tactical logistics planning systems, corn is electronic brainstorming and assumption surfacing. prised of data based management systems, fourth A question to be solved is displayed on the wall, and generation languagesand optimization baseddecisior everyone enters an anonymous response, which is support models, are helping operating management at presented on the screen. Files are exchanged anony- W. R. Grace make decisions that achieve better re- mously and people are free to speak out. Forceful source utilization and exploit comparative advantages. personalities who tend to dominate verbal brainstorm- In "A Logistics Planning System at W. R. Grace," ing sessions lose that power when the discussion goes Darwin D. Klingman, John Mote and Nancy V. electronic. The system results in more equal input Phillips discuss how these systems assist management time for all participants and it speeds up the flow in making decisions by giving them easy access to data of information. The process differs from tele- and analysis. The models process data on the supply conferencing because participants are in the same movement and storage of materials and finished goods room and they interact simultaneously; unlike tradi- to help managers understand the implication of pos- tional brainstorming, there is no crosstalk or side sible actions and policies. Optimization models pro- conversation. Participants concentrate on the task, vide management with an1ticipatory feedback by pre- focusing on ideas rather than on the proposers. Man- scribing appropriate logistical directions and detailing agers seem to like the candor the process allows. likely operating results in time for management to Considerable deliberation and negotiation on issues exercise control, exploit opportunities and preclude occurs. Alternatives are generated and uninhibited undesirable outcomes. As a consequence, firms are communication takes place. The electronic medium investing in technology to support and improve the supports a new way of getting individuals to work as quality of logistics planning ahead of or in parallel a group-an exciting process that is described in with investment in engineering based improvements "Computer-Aided Deliberation: Model Management in production and distribution. They recognize that and Group Decision Support" by J. F. Nunamaker, helping operating management make betterdecisions Lynda M; Applegate and Benn R. Konsynski. The is necessary to realize the cost savings from increasing authors forecast that this type of software will accom- the technological sophistication of production and plish for group work environments what time sharing, distribution resources. A number of companies are multiprogramming and multiprocessing have done for coupling their information systems with tactical logis- the individual computer user. tics models to improve the cost and service effective- ness of business decisions. Managing Decision Models

Each year billions of dollars and millions of hours are Making Group Decisions by C.omputer spent to develop computer based models for decision

Automated support for decision making in organiza- support systems. Additional resources are allocated to tions has undergone significant development since it learning, using and maintaining these models. This was first proposed in the early I 970s. While studies indicates that models, as an organizational resource,

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In This Issue / 809

need to be managed properly. Although the con- project specific items as soon as they can. This practice cept of model management may be traced to the brings about excessive inventory costs, without nec- IBM Scientific Subroutine Library developed for essarily improving on-time delivery. Boaz Ronen and FORTRAN programmers in the 1 960s, most recent Dan Trietsch generalize the newsboy model to optim- research adopts a broader view and considers model ize purchasing orders, and their paper ("A Decision management systems as software environments that Support System for Purchasing Management of Large support model builders and users in the model devel- Projects") describes a DSS that applies a simple heu- opment and decision making processes. One impor- ristic based on their model. The DSS can also be used tant aspect of this support is that the system provides to improve planning while bidding for a project and advice on model construction, integration, and utili- as a negotiating tool with clients and other suppliers. zation. In "Development of a Knowledge Based Model Management System," Ting-peng Liang pre- The Three-Dimensional Gantt Chart sents a software architecture for developing a knowl- Decision support systems have traditionally empha- edge-based model management system and a graph- sized the importance of the user interface to deliver based mechanism for constructing larger models from analytical tools. At the heart of the user interface are smaller building blocks. the representations of the problem at hand and its

possible solutions. For production scheduling, the Managing Funds in a Public Unversity two-dimensional Gantt chart, invented by Henry

The management of funds in a large public university Lawrence Gantt at the beginning of this century, has is an uniquely difficult problem. Since the allowable been adopted widely to provide a clear representation use of funds often depends on the source of the funds, of production schedules. With the increasing availa- elaborate information must be maintained on all bility of interactive computer graphics, the Gantt chart funds in terms of source and use. This is accomplished has been married to sophisticated scheduling algo- by the so-called funds accounting used by most uni- rithms in an attempt to combine human experience, versities. However, accounting information is often intuition and pattern finding skills with the numerical fragmented among various, semi-independent organ- speed and sophistication of the algorithms. As com- izational units. For example, auxiliary enterprises and puter graphics capabilities improve, however, new university services often are relatively independent of representations become possible. In "The Three- instructional services and operations. Most universi- Dimensional Gantt Chart," Christopher V. Jones ties have a foundation or an endowment fund for explores a three-dimensional extension of the private donations, which is somewhat independent of Gantt chart that combines some commonly used state and federal appropriations. The decision support two-dimensional Gantt charts. The graphics capabili- system described in "Funds Management in a Large ties that allow a three-dimensional representation also Public University" (by Rajesh Tyagi, Laurence Moore facilitate animation and animated sensitivity analysis. and Bernard Taylor) provides a comprehensive over- view of all university funds by source and needed Describing Decision Support Systems expenditures, either requested or budgeted, by cate- A central tenet of the literature says that decision gory of use, and a model for allocating funds from systems must be specific to the decision making en- source to use categories. The system is on-line, user vironment they support. Much research has addressed friendly, and allows university management to specify ways to differentiate environments-for example, multiple criteria for funds allocations. identifying differences among decision makers, prob-

lem solving tasks and organizational settings-but Scheduling Purchasing Orders for Large Projects relatively little effort has been spent on describing and Production by contract is typically encountered in the differentiating the systems. Ultimately, those who buy defense industry, and calls for project management or build DSS should be provided with a prescriptive techniques, such as PERT. When the contract is for mapping from decision making environments. To R&D, the duration of each activity is a highly sto- support such research, however, a meaningful way to chastic variable; the bulk of the PERT literature fo- describe and compare DSS must be developed. In cuses on this element. For a manufacturing contract, "Descriptive Analysis for Computer-Based Decision however, the practical experience is that the variability Support," Mark S. Silver presents a three-tiered ap- of supply lead times is the major stochastic element proach for characterizing decision support systems. in the picture. Facing high delay penalities, which are The first tier analyses a system's functional capabili- typical of this environment, managers tend to order ties, addressing the question, "What can the DSS do?"

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810 / In ThisIssue

The second level considers a system's components as nary assessment of routing costs to serve customers in seen by its users, and asks, "How does the DSS ap- resource planning, the location of depots when a pear?" The third tier examines a system's attributes or vehicle visits more than one customer in a facility, its characteristics as a whole, and concentrates on the and in nonrouting contexts such as job sequencing question, "How will the DSS affect decision making?" and object ordering.

Mass Screening Models for Contagious Diseases Scheduling With Precedence Constraints

The AIDS epidemic has engendered considerable pub- Considerable research has been done in stochastic lic concern. There have been calls for widespread scheduling, especially to investigate the structure of screening for the presence of the human immuno- optimal scheduling policies for jobs with random pro- deficiency virus seropositivity in various sectors of the cessing times on parallel machines. Under some population so as to curb the spread of the deadly processing time distribution assumptions, optimal disease. However, little is known about the costs and policies were found for various objective functions. benefits of such testing programs. Prior to this re- Sometimes, scheduling jobs on parallel machines sub- search, William P. Pierskalla studied the problem of ject to precedence constraints were considered. Such the optimal design and quantification of the costs and scheduling problems have applications in industry. benefits of mass screening programs for nonconta- Consider an assembly line designed to produce a single gious diseases. With the growing alarm of the spread product that is composed of several elementary parts. of infectious diseases, he and Hau L. Lee extended The job of producing the most simple parts must that work to the screening of contagious diseases. The precede the job of putting together these parts in order theoretical and conceptual results of this investigation to construct more complicated subassemblies, which are presented in "Mass Screening Models for Conta- precedes the job of fitting together the subassemblies gious Diseases With No Latent Period." The authors to form the final product. Precedence constraints also introduce a stochastic model that considers the un- play an important role in the computation of compli- derlying mechanisms for the spread of disease. The cated mathematical expressions, where some terms model generates an optimal screening schedule. This have to be computed before others. In this paper paper uses the methods and concepts of reliability ("Stochastic Job Scheduling Problem With Intree theory for the analysis of an important health policy Precedence Constraints"), Esther Frostig combines issue. Factors of test reliability and patient treatment theory and the results of scheduling stochastic jobs on noncompliance are also considered. The authors are parallel machines with some results for scheduling working on applying the model to diseases such as jobs on parallel machines subject to precedence con- hepatitis B and AIDS. straints in order to characterize the optimal policy for

Designing TSP Tours With Good Properties scheduling stochastic jobs on two parallel machines.

It is common practice in many delivery and collection Stability for Multidimensional Stochastic Systems services to skip customers on predesigned routes and . . serve only the ones with requests. Examples include abilit s a fd ea ise ofasyste pform- the delivery of hot meals, warehouse bin retrievals, ance. should precede gardtaed analysistofcany ' . ' ~~~~~system because stability guarantees the existence of and mail delivery. The reasons for not reserving routes well behaved properties for the system. In a broad may differ each time, depending on the service being

sense, a system is stable if it possesses required prop- offered: the system's operator may not have the re- . ' . sources (time or material) or the information (who is etiestin teprence o som disturbances in to be visited before the route starts), or may have other .sochastictproach To em .analysis, trffcds priorities, such as achieving regularity and personali- a source of dsturbances. Then stablty sense depends

' . . . . ~~~~~~~on what one understands of the required property. zation of service by having the same vehicle and driver Existence of the steady state probabilities or conver- assigned to the same route. The problem is to define . .. gence in probability lead to stability in the sense of good, predesigned routes. Yet, until recently, this skip- ergodicity. Requirements of finite moments for some ping strategy was not taken into account explicitly quantities, such as queue length and waiting time, is during the design of the route. In "A Priori Solution a f o so n of a Traveling Salesman Problem in Which a Random....' Subset of the Customers Are Visited," Patrick Jalllet Cniin o utdmninlQeen ytm defines and analyzes a generic model for such situa- WihCmue plctos"W zakwk tions. The model can also be applied to the prelimi- (continued on page 969)

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Contributors / 969

Bernard W. Taylor III is the R. B. Pamplin Professor of Management Science and Head of the Department of Management Science in the R. B. Pamplin College of Business at Virginia Polytechnic Institute and State University. His participation in this research stems from his interest in the application of optimization models within a DSS framework. He is currently Program Chair and President-Elect of the Decision Sciences Institute.

Dan Trietsch, see Boaz Ronen.

Rajesh Tyagi is an assistant professor of management information systems at the University of Alabama, Huntsville. This research evolved from his Ph.D. dis- sertation prepared at the Virginia Polytechnic Institute and State University. His current research activities include developing scheduling algorithms for incor- poration in decision support systems for the mission planning and scheduling process at NASA.

IN THIS ISSUE (continued from page 810)

provides criteria for ergodicity of multidimensional Markov chains. In the multidimensional environ- ment, these criteria are sufficient, but unfortunately, not necessary. To study the necessary conditions for ergodicity, W. Szpankowski and V. Rego ("Some Theorems on Instability With Applications to Mul-

tiaccess Protocols") propose to investigate sufficient conditions for nonergodicity. They also suggest that in the multidimensional environment, another kind of instability, that of finite moments, is better to study. This instability is easier to verify and is practically sound.

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