Modeling and Simulation in Manufacturing and Defense Acquisition Pathways to Success (2002) / Chapter Skim
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5 Modeling and Simulation Research and Development Topics
5 Modeling and Simulation Research and Development Topics
Pages 77-102
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From page 77... ...
In its statement of task, the committee was asked to investigate emerging M&S technologies, assess ongoing efforts to develop them, and identify gaps that would have to be filled in order to make these emerging technologies a reality. The committee rephrased this task and sought to determine those M&S topics requiring R&D in order for M&S to be effectively used in commercial manufacturing and defense acquisition.
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From page 78... ...
To scale by a million, an application's storage and processing capacity would have to be able to grow by a factor of 1 million just by adding more resources (NRC, 2000~. This implies that as a system expands or as performance demands increase, the underlying architecture must support the ability to reimplement the same functionality with more powerful or capable infrastructure, for example, replacing a single server with a highperformance server farm.
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From page 79... ...
_ - , ........ _ Node capability 13IT- Infrastru~L`~e Level Current and foreseeable trends are to employ object-oriented technology to enable scalability attributes.
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From page 80... ...
Distributed simulation systems are being developed to support interoperation of such model families (Davis, 2001~. Agent-Based Modeling Agent-based modeling is a modeling method based on the simulation of what are called low-level entities, such as individual people or aircraft, that have simple behaviors but that can produce complex and unexpectedly realistic collective, or emergent, behavior (Epstein and Axtell, 1996~.
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From page 81... ...
, and avoiding ad hoc assumptions during model development (Cederman, 1997~. Semantic Consistency Semantic consistency, also known as substantive interoperability, refers to consistent phenomenological representations of real-world systems and processes among interacting distributed simulations.
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From page 82... ...
They are not optimization algorithms that have been modified to run under computational resource constraints, such as tree searches that are cut short when time or memory runs out. Typical FFA schemes exploit minimal knowledge, such as object recognition and other one-reason bases for choice making under time pressure, elimination models for categorization, and "satisficing" heuristics for sequential search.
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From page 83... ...
The statisticsoriented approach deals with prediction and management of uncertainty, whereas the computer-science-oriented approach deals with interoperability, reusability, integration, distributed operation, and human/machine interfaces. The computer-science-oriented approach is necessary for the future operational success of defense acquisition and commercial manufacturing, but as processes and systems become increasingly complex, estimation and management of uncertainties will become increasingly important.
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From page 84... ...
In many complex decision problems, it is often sufficient to be able to determine which solution is better, or to determine which is in the top 1 percent, rather than which is the absolute best. A theory of ordinal optimization is being developed that may enable quantitative measurements of such assertions via simulation modeling without having ' Y.C.
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From page 85... ...
Tabu search is a heuristic technique for search in combinatorial optimization problems (Grover, 1990~. Errors in Distributed Simulations Given fixed resources and a model complexity that exceeds these resources, a trade-off must be made between size and resolution.
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From page 86... ...
However, since distributed messaging requires that continuous quantities be coded into discrete packets and sent discontinuously, it is more appropriate to consider discrete event simulation as a natural means to consider accuracy or bandwidth trade-offs. Recent work has shown that significant reductions of message bandwidth demands (number and size of messages)
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From page 87... ...
This infrastructure must support model integration and interoperability in order for the M&S requirements of acquisition and manufacturing to be met. Important topics associated with model integration are interoperability, composability, integrating heterogeneous processes, and linking engineering with effectiveness simulations.
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From page 88... ...
Although common data-interchange mechanisms and formats such as HLA and XML can support technical interoperability by enabling simulations to communicate, they do not guarantee substantive interoperabi] ity because they do not ensure that the communicated data are correctly usable by the receiver.
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From page 89... ...
As it matures, SEA will require common frameworks for models with temporal dynamics that are used in a great variety of components within DOD systems, such as flight control systems and operator training systems. Such frameworks must be capable of expressing a large variety of model formalisms, including traditional
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From page 90... ...
While many modeling frameworks and simulation systems have the expressiveness and performance capabilities to some extent, no single commercially existing product can support both to the level demanded by the SEA concept. Integrating Heterogeneous Processes Virtual environments offer a sense of immersion into reality with true-to-life graphics and animation.
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From page 91... ...
More generally, interfacing abstract models with real-world processes requires that the logical time base of the simulation be synchronized as closely as possible to the clock time of the underlying computer system. Work related to real-time simulation and control includes early research in DEVS-Scheme, the extension of the discrete event system specification (DEVS)
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From page 92... ...
New approaches are needed (Ghosh and Grambasi, 20011. Linking Engineering and Effectiveness Simulations It is useful to distinguish between two broad classes of simulations.
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From page 93... ...
The ability to link these two types of simulations is necessary for achieving the goals of defense acquisition. The ability to reuse engineering models and simulations in effectiveness simulations would save time and money.
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From page 94... ...
Physics-based modeling is arguably more important for defense manufacturing and acquisition than for other simulation applications such as training. Human Behavior Modeling Computer-generated forces are often used in training simulations to provide both opposing forces and supplemental friendly forces for human participants in a simulation.
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From page 95... ...
systems, operational testing has seen a gradual increase in the use of M&S to reduce time and costs. This application of M&S requires extremely accurate simulations and consequently requires highly reliable validation methods.
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From page 96... ...
The development and application of standards, however, are essential to the achievement of the level of interoperability, integration, and reuse envisioned for commercial manufacturing and defense acquisition. This section discusses existing modeling and simulation standards, general software standards, and higher-layer standards, and needs for their development and integration.
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From page 97... ...
Objectoriented modeling languages have already demonstrated how objectoriented concepts can be successfully used to support hierarchical structuring, reuse, and evolution of large and complex models independent of the application domain. Noncausal modeling demonstrated that the traditional simulation abstraction can be generalized by relaxing the causality constraints, or by not committing ports to an input or output role too early.
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From page 98... ...
Other advantages of the object-oriented approach include support for scalable high-performance execution and model development; dynamic reconfiguration; systematic and incremental verification and testing; and team-oriented development. The adaptation of object orientation to software engineering has become increasingly indispensable for systems exhibiting heterogeneity and demanding flexibility in terms of both software and interoperability with multiple hardware components.
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From page 99... ...
Common Object Request Broker Architecture Middleware technology evolved during the 1 990s to provide interoperability in support of the move to client/server architectures. The most widely publicized middleware initiatives are OMG's CORBA, Microsoft's distributed component object model (DCOM)
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From page 100... ...
Middleware services are sets of distributed software that exist between the application and the operating system and network services on a system node in the network. Middleware services provide a more functional set of application programming interfaces (APIs)
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From page 101... ...
During the last several years, significant progress has been made on the XML3 for data exchange. XML is applicable to the exchange of virtually any type of data, and a number of business and technical communities have developed associated standards using nomenclature common in those individual communities.
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From page 102... ...
Advances in technology, such as parallel computing, distributed computing, and distributed simulation, have begun to make integration and interoperability of simulation systems practical. However, the breadth of the comprehensive SBA vision, including model integration across all of the SBA viewpoints, is beyond current hardware and software capabilities.
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