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原文：
The role of system dynamics in project management
语文作文600字
John Bowers，Alexandre Rodrigues.
International Journal of Project Management，1996，14(4)：213-220 Introduction
Whereas the traditional project management tools provide uful support, their underlying models often em to bear little relation to actual projects. The traditional approaches tend to assume that if each element of the project can be understood then the whole project may be controlled. However, experience suggests that the interrelationships between the project's components are more complex than is suggested by the traditional work breakdown structure of project network. An alternative view of the project is offered by system dynamics which concentrates on the whole project. The approach emphasis the interrelationships that may be responsible for unexpected overrun and overspend. System dynamics has been applied in a number of projects in diver industries, providing a basis for a comparison with the traditional approaches. It offers valuable strategic lessons for project management and should be en as complementary to the detailed operational support supplied by the traditional techniques. This paper contrasts the characteristics of the two approaches and provides
曲线方程公式an overview of various areas of application of system dynamics in project management. It highlights the distinctive contribution that system dynamics can make to project management, while emphasising that the more traditional techniques still have a vital role. Copyright © 1996 Elvier Science Ltd and IPMA.
A new approach to modelling and understanding projects is emerging, bad on system dynamics. System dynamics assumes a holistic view of the organisation focusing on the behavioural trends of projects and their relation with managerial strategies. The approach contrasts with traditional methods, which rely on detailed models of the components of a project with the main object of providing tactical advice about the resourcing and scheduling of activities. There has been a tendency to produce ever more sophisticated network-bad tools, in the belief that by incorporating more detail a more accurate model will be developed and a greater understanding will be the inevitable result. However, it has also been suggested t'2 that concentrating on the detail ignores many of the major, but not readily quantified, influences that cau project failure, and that a new approach is needed taking a more systemic view. System dynamics provides the opportunity of such an alternative view, considering the major influences on a project and dispensing with much of the detail to ensure that the key behaviour of the project is not obscured. Typically, system dynamic studies offer general conclusions
about Author for correspondence. project behaviour but it is not always obvious how such advice might be incorporated into a daily project plan.去黑头小妙招
The traditional approaches have many failings and it appears that system dynamics may offer a uful alternative, but is it of practical value to the project manager? This paper examines the applications of system dynamics to project management and its potential roles in comparison with the more traditional techniques of project analysis.
Characteristics of the traditional approaches
Numerous techniques have been developed to help manage project schedules and costs. The techniques are founded on the premi that whereas a project may be unique, many of its constituent elements have been experienced before. The project work is therefore decompod into elements, for example activities, which can be individually related to previous experience. It is then possible to produce reasonable estimates of the duration, cost and resource requirements for each element. The logic of the project, such as reprented in a network, supplies the basis for reconstructing the project from its elements and calculating the duration, cost and resource requirements of the whole project from tho of its elements. One of the concerns about such an ap
proach is that, whereas the estimates for the individual elements may be very accurate, the reconstruction of the project may ignore important intra-project forces: the whole may be much greater than the sum of the parts.
The traditional analys of projects have been described as linear or as "static and clod TM, suggesting an assumption of a strictly ordered project that progress in well defined, predictable stages to completion. This includes an assumption that all the information is available at the start of the project, allowing the design of an optimal plan and the only concern of management is to keep the project on the specified track. However, in practice, management needs to be dynamic, responding to new information and adapting the plan rather than keeping rigidly to the original. When implemented properly, the traditional methods are ud in a more responsive manner, deployed within the dynamic environment of the classical control feedback loop: the original plan is ud to t targets which are then compared to progress and where there is significant deviation, action is taken including revisions of the project plan. Whereas individual tools might be very linear in nature, the overall framework of traditional project control exhibits the classic characteristics of a dynamic system.
The system dynamics approach
System dynamics was introduced by Forrester 4 as a method for modelling and analysing the behaviour of complex social systems, particularly in an industrial context. It has been ud to examine various social, economic and environmental systems 5, where a holistic view is老奸巨猾
important and feedback loops are critical to understanding the interrelationships. The approach has attracted particular attention in recent years since computer software has become readily available to help communicate the key dynamics of systems to the managers responsible.
Having identified the key feedback loops and various disruptive factors, quantitative estimate of the different effects are elicited, either from data describing past projects or in discussions with various project participants. A computer-bad system dynamics simulation model may then be built, using software such as PowerSim (ModellData AS, Bergen, Norway) or iThink (High Performance Systems Inc., Hanover, Hampshire, USA). The graphics of such models allow the effects of the feedback dynamics to be obrved, leading to a greater understanding of the system and encouraging experiments to explore new management options.
The application of system dynamics to project management has been motivated by various factors:
• a concern to consider the whole project rather than a sum of individual elements (the holistic appro
ach),
•the need to examine major non-linear aspects typically described by balancing or reinforcing feedback loops,
•a need for a flexible project model which offers a laboratory for experiments with management's options,and
• the failure of traditional analytic tools to solve all project management problems and the desire to experiment with something new.
Applications in project management
The system dynamics model of a project aims to capture all the major feedback process responsible for the system behaviour. The project management process is put into a wider context which includes many soft factors often external to the project work, with a strong focus on human factors which often appear to dominate the feedback structures. The developments of system dynamics in project management are summarid in Table 1, which includes a reprentative sample of studies drawn from a more exhaustive review 6. The first description of the u of system
dynamics in understanding projects appeared in 1964, but it was not until the 1980s that the first project-specific applications began to be reported. Since 1990 there have been many more reported examples of the u of system dynamics in project management.
Typically the application areas are tho where budgets are high and the risks greater, such as aerospace, software developments and recently the Channel Tunnel. The first models 7"8 were developed to examine the dynamics of rearch and development projects. The
concepts of perceived progress and real progress were introduced, addressing explicitly the fact that managerial decisions are bad on perceptions of the project's state which may be quite different to the reality. Richardson and Pugh 9 dev- eloped the model of the R&D projects, and various studies investigated the new concepts of rework, undiscovered rework, perceived progress, real progress, perceived productivity and real productivity. The "program management modelling system, developed by Pugh-Roberts Associ- ates, incorporates many of the features and has been ud to support the management of veral large projects. Other studies have examined specialid application areas, such as tho of Abdel-Hamid ~H6 in the management of software development projects.
Comparing system dynamics and traditional approaches普拉提是什么
Both the system dynamics and the traditional approaches examine the same basic issues in project management but from very different perspectives; a summary is provided by Table 1.
Table 1 Comparison of the characteristics of the traditional and system dynamics approaches
Aspect Traditional approach System dynamics approach
Focus Project work and the "problem"Feedback process and the "situation"
Level of detail Considerable detail in some areas but
蔓延的读音ignores others
Little detail but attempts to capture the whole
project
Factors considered explicitly The readily quantified and tho related to
project work
The subjective and tho related to feedback
process
Key factor The logic of work and its resource
requirements
Human resources' behaviour
Project work
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A t of interrelated but distinct packages A continuous flow
Nature of estimate Predictions assuming success, reflecting a
desired outcome
A simulation of reality, including human and
system frailties, indicating likely outcome
Incorporating system dynamics and the traditional approaches
A system dynamics analysis offers a distinctly different view of a project with the main output being a better understanding of the important underlying influences. As such, system dynamics appears to be complementary to the traditional techniques rather than a complete alternative. Various routes might be adopted to incorporating the two approaches:
•a more sophisticated network model including the feedback process and detailed mechanisms for modelling activity durations and costs to reflect the underlying influences;
• a more detailed system dynamics model distinguishing the major stages of a project as distinct activities and employing different types of project work;
• assimilating the main lessons from system dynamics studies in a t of rules for u in estimating activity durations, costs and uncertainties
Conclusions
The traditional techniques are bad on a detailed breakdown of the project into work packages and activities; this permits the construction of equally detailed schedules and budgets for the control of th
e project and provides the basis for operational decisions such as resource allocation and time-cost trade-offs. System dynamics offers a project model which appears to reflect the real experiences of projects which ldom follow the simple linear route suggested by the logic of the project network. System dynamics suggests that it is not the detail that determines the outcome of the project but the powerful underlying influences and the insidious feedback loops that can, if not managed properly, result in unexpected overrun and overspend.
Whereas there are examples of system dynamics being ud in projects in a range of industries, it is still a relatively rare technique and tends to be employed within parate studies when a special concern aris in a project. The two ap- proaches provide valuable complementary information: the traditional techniques supply the detailed output necessary for project control, whereas system dynamics offers uful general strategic lessons which should be considered when planning the project and producing the estimates for the traditional analys. There should be benefits in formally incorporating the two models but it is vital that the clarity and fresh vision introduced by system dynamics is prerved.
