VSO is a powerful, easy to use Colored Petri Net based, system architecture tool for the Microsoft Windows platform. The unique power of VSO comes from the ability to design an executable architec ture as simply as other tools, such as IBM System Architect.

Executable architecture allows a subject matter expert to simulate the dynamic characteristics of
a system over time. Key features of VSO include:

The ability to allow subject matter experts to build individual business components used by an architect to assemble the executable architecture.

The ability for executable components to be constructed without writing code (although code libraries are optionally supported).

Support for the Department of Defense Architecture Framework (Department of Defense Architecture Framework (DoDAF)) in VSO architectures.

The ability to execute "what-if" scenarios and perform goal-seeking through iterative execution and results logging and analysis.

The mathematical rigorousness of Colored Petri Net technology.

The ease of use of a Windows application with a standard user interface.

VSO allows any organization’s subject matter experts and architects to perform complex business intelligence analysis using proven technology and an intuitive interface.

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Visual Simulation Objects (VSO) has been described by the U.S. Air Force Research Laboratory (AFRL) as the ?Next Generation? architecting tool.

It is the product of over 50 man-years of effort funded by eleven Small Business Innovative Research (SBIR) contracts performed over the past seven years.

VSO has been developed with one goal: to expedite responsible decision making and accountability by the detailed analysis of business operations and systems.

While such investigations have always been performed in special cases, the Klinger-Cohen Information and Management Technology Reform Act of 1996 mandated it for new programs and thus became the prime mover for a renewed interest in describing complex operations and systems in a way that would enable a detailed mathematic analysis to be performed, the results of which would provide a way to evaluate and rank alternative architectures.

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Subsequent to the Klinger-Cohen Act, architecting became a pervasive activity in all Government organizations, and, as would be expected, problems arose almost immediately. Initial meetings with VSO’s developers (Expand, Inc.) and Government program and technical managers (AFRL and USAF Electronic Systems Center) identified three important concerns with the existing state-of-the-art in architecting methodology:

It takes too much effort to develop an architecture and there are not enough resources available to build a robust architecture.

The time required to modify an existing architecture is too long to satisfy the requirements
of real-time decision makers.

The architectures being developed lack the fidelity needed to obtain operationally
predictive results. This is due, in large part, to the poor interface between the participants in
the architecting effort: subject-matter experts, who understand systems and operations, but not software, and
the software developers, who understand software, but not systems and operations. Additionally, the architecting methodologies were generally not based upon principles that were mathematically sound, or at least had not been demonstrated to be so.

Expand, Inc. was challenged by the Government to:
(a) reduce the development time by 50%;
(b) reduce the time required to create a variant of an architecture by 75%; and
(c) use a proven, mathematically well-founded methodology that would dramatically
shift architecting away from the software engineer and to the subject-matter expert.

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VSO is a Personal Computer application that executes from the Windows operating system. As such, it has a familiar user interface similar to MS Word and PowerPoint. At one level it is simply a drawing tool that can be used to describe operations and systems. The user selects objects (aircraft, computer, business activity, etc.) from a tool bar and drags and drops them in a design area.

The objects can be connected together to show information and data flow appropriate for a proposed architecture. However, a number of important functions are being performed beneath the surface that verify and validate the architecture. Although the user is not explicitly aware of it, he is actually describing the architecture as a Colored Petri Net (CPN).

The objects (library objects are available or the user can build custom objects and store them for re-use) have embedded within themselves a complete mathematical description of their static and dynamic properties.

This means that the architectures developed in VSO can be made to evolve over time by simply clicking a Start button. Evolution over time occurs because VSO objects contain the business rules that dictate their behavior ? that is, the changes in the values of the architecture?s attributes that occur as explicit functions of time or upon the occurrence of an event.

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High Level Architecture (HLA) Interface.

An architecture can be extended to a simulation by adding environmental conditions, realistic scenarios and adversarial actions. Often validated programs exist that provide these conditions. In such cases, a VSO architecture can interface with these programs through its HLA interface. The federation of a VSO executable architecture and one or more simulations executes seamlessly within VSO.

Architecture Framework (AF).

Department of Defense Architecture Framework (DoDAF) products can be integrated with the architecture so that changes to the architecture automatically re-generate a set of DODAF products. This ensures that the DODAF products and the architecture are consistent.

Colored Petri Nets (CPNs).

The executable architecture is a CPN and, as such, it inherits the formal definition, mathematical rigor and verification capability of CPNs.

Architecture Openness.

VSO architectures can be saved as either binary or tagged-data (XML) files. This allows them to be used with other applications. Additionally, VSO architectures can be executed from other tools using a library of functions provided with the tool.

Data Logging.

Data generated by VSO during execution is saved in XML format for post-execution analysis
by other tools.

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