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Abstract
The Department of Defense has focused much attention in recent years to the use of modeling and simulation for developing and analyzing the military systems of the future. Decreasing budgets, coupled with the necessity of being prepared for multi-faceted types of military activities, such as humanitarian interventions, joint peacekeeping efforts, and other “Missions-other-than-War” have created a need to prepare for unforeseen missions. There is also a requirement for the military to attempt to try out unfielded and evolving weapon systems and technologies to see how they might affect their tactics, techniques, and procedures. This analysis is being done by means of modeling and simulation, from conventional (live action) war-gaming to completely virtual simulations. Constructive simulations are being used by the Army to determine the affect of new technologies on Command, Control, Communications, Computers, and Intelligence (C4I). Capturing high-level, contextual information as well as sharing data objects can enhance simulation interoperability. The HLA (High-Level Architecture) consortium has established a standards infrastructure to make individual simulations interoperable. Specifically, the IEEE P1516.2 Standard for HLA OMT (Object Model Templates) prescribes a format to support the reuse of Simulation Object Models (SOMs). This standard has been ported to XML. XML has been used to represent computer-generated forces in military simulations tools, such as OneSAF (Semi-Autonomous Forces). There is a major effort in the simulations community, called XMSF (Extensible Modeling and Simulations Framework), to propose a set of standards, processes, and practices to incorporate XML and web services. Our research effort has defined an XML-based specification grammar, SCML (Scenario Markup Language) based on an ontology of narrative. SCML can be used to support simulations, course-of-action analysis, battle planning, and other decision-oriented applications. This paper will examine these current efforts to incorporate XML and XML technologies into the military decision-making process.
Keywords
Table of Contents
The military has changed drastically since the end of the cold war. The digital battlefield has replaced the large-scale deployments that use heavy equipment and antiquated regulations. The massive amounts of information need to be in a flexible format that can be transformed readily to support disparate systems. The army is increasingly moving towards XML technologies for knowledge representation.
The purpose of this paper is to present a brief description of how the military is taking advantage of XML. There are ongoing projects to design the appropriate XML languages and tools to support military objectives. This paper will also highlight an XML specification developed at the Army Research Lab (ARL) to assist policy makers and system developers.
There is a requirement for the military to try out experimental systems to gauge their impact on doctrine and training. Most of this analysis is done through computer simulations. Virtual wargames with actual army units are used to assess the effect on Command, Control, Communications, Computers, and Intelligence (C4I).
OneSAF (Semi-Autonomous Forces) is one of the more prominent examples of the standard simulation environment. Low-fidelity virtual objects representing tanks, scout vehicles, artillery units, and other combat platforms interact on a digital terrain. (See Figure 1) OneSAF simulates the hierarchy of military units and their associated behaviors. The participants run the simulation from static mockups of battlefield vehicles, using onboard computer systems with collaborative technologies (shared whiteboards, digital radios, etc.) to view the battlefield. [OneSAF]
The fundamental components within the environment are behaviors, physical models, and behavior agents. The behaviors contained in OneSAF are low-level functions based on doctrine. Software agents control planning and manipulate the behaviors. Complex behaviors are created in a behavior definition language (BDL). An XML schema has been developed for mapping to BDL and representing these composite behaviors, specifically temporal and data dependency relationships.
Many simulations are "stove-pipe" systems, able to send data to other applications within the same domain but not across boundaries. There are instances where the logistician and the commander would benefit from sharing the same simulations data. This type of interoperability requires a set of standards for describing the structure and relationships between simulations. The High-Level Architecture (HLA) standards were developed to create a common architecture applicable across all types of simulation environments. The HLA Working Group has developed the following standards:
Framework and Rules (IEEE P1516) – defines the standard Simulation Object Model (SOM) for HLA-compliant systems.
Federate Interface Specification (IEEE P1516.1) – describes the interactions between simulations and a Run-time Infrastructure (RTI).
Object Model Template (OMT) Specification (IEEE P1516.2) – the objects, attributes, interactions, and parameters that are required for a SOM.
The OMT Data Interchange Format (DIF) supplies a structure used by automated tools to convert from one representation of an OMT to another. Initially, the OMT DIF was presented in Backus-Naur Form, a standard technique for formal representation a hierarchy of information. There is now available an XML version of the OMT that will leverage many existing tools and techniques for interchange.[OMT]
In order to share higher-level information between simulations, it is necessary to describe the context under which SOMs are manipulated within each simulation. Interoperability at this level requires meta-models, adaptive models, and common repositories. The Model-Driven Architecture (MDA) initiative has been introduce to create specifications based on formal models. Under the MDA, models take advantage of technology such as the XML Metadata Interchange (XMI) specification, Simple Object Access Protocol (SOAP), and other standards.[Tolk02]
Military planners now have to deal with large amounts of information coming from distributed and disparate systems. There is also a necessity for different levels of access to the information and multiple bandwidth requirements for the transmission media. XMSF is an initiative that seeks to use web-enabled technologies to support distributed simulations. The primary position of XMSF is that web-based technologies have the capability to support scalable interoperability of DoD models and simulations and integrate distance-learning technologies for training.[Pullen]
XML is considered the primary bridge between commercial web standards and developing simulation environments. XML can also be used to map legacy simulation environments into the distributed, interoperable frameworks being developed within HLA. From an economic standpoint, the XMSF effort seeks to leverage the best business cases for web-enabled enterprises from the commercial sector, shortening the length of time for fielding new systems and improving interoperability with existing standards.[Tolk03]
The difficulty in developing a meta-model for simulations rests in the numerous styles, categories, and implementations of simulations. It is necessary to find an abstraction of simulation environments that can describe the concepts within any simulation, without being tied to a specific context. All simulations are essentially stories. They are stories about what was done, what is being done, or what can be done. These different forms of narrative can be used for problem solving, training, entertainment, and any other activity that involves decision-making.
A scenario is defined as a form of narrative consisting of a collection of episodes with the purpose of describing the actions of characters within an environment.[Hobbs00]Scenario-based design has become a powerful technique for system specification and design. The entire software development life cycle from requirements gathering, architecture descriptions, prototyping, implementation, and software maintenance involves some level of scenario descriptions.[Potts]
Scenarios have been used in software engineering, cognitive science, and HCI (Human-Computer Interaction) to aid in decision making, comprehension, design, and training. [Carroll] Creating scenarios drive the discussion in collaborative activities and increase understanding in single user tasks. These "what-if" studies refine the design and requirements of a system before implementation, isolating potential system errors and design problems early in development.
Ontology for narrative has been defined to support a specification language framework for scenarios. The conceptual model evolved from the analysis of multiple narrative domains, detecting commonalities of story elements.[Hobbs03Spr] This led to the creation of ontology for decision-oriented narrative and the relationship between story elements. There are two aspects of narrative scenarios: (1) the static structure of the content, and (2) the dynamic storytelling process. These scenario artifacts can be authored, shared, and analyzed using the appropriate software tools. A markup language framework allows the separation of structure from application. The semantic information within narrative and the relationship/hierarchy between story elements is represented structurally with tags and attributes in a specification grammar. Figure 2shows the narrative ontology represented as a UML (Unified Modeling Language) class diagram. The diagram establishes a hierarchy of story elements and the associations among them.
The fundamental building block of a scenario is the action. Meaningful sequences of actions make up events, and predetermined lists of events are combined into episodes. Episodes are goal-oriented, containing events that support sub-goals. Scenarios are a succession of episodes (goals) that were either achieved or thwarted. The hierarchical nature of the scenario structure affords manipulation of the story.
The goal of the research was to represent the structural and linking models in a form that is general enough to describe the structure of a scenario and expressive enough to support different external views of the data. The choice of a markup language supports both these objectives. The ontology has been translated into an XML grammar called SCML (Scenario Markup Language). Documents rendered in SCML are referred to as Hyperscenarios, due to the multiple linking capabilities of the format.
The value added of SCML is realized through the use of XML Style Language (XSL) transformations. Multiple story views (such as hierarchical, summary, storyboard, and literary narrative) can be made available for analysis. Existing XML technologies, like VoiceXML, can be used to generate an audio version of the story with the help of an appropriate text-to-speech engine.
Analyzing the artifacts and processes of an organization determines episodic information for creating reasonable stories in a domain. The military domain is well suited for depiction using hyperscenarios, because of the established doctrine for any activity. It is straightforward to determine potential episodes, actors, actions, and events from army field manuals, policy documents, and regulations. [Hobbs03Fa]
There are several decision-making and comprehension tasks done by the military that are candidates for this representation:
After-Action Reports
Knowledge representation for lessons learned repositories
Knowledge exchange format for intelligent software agents
Scenario Authoring for M&S systems
Course-Of-Action (COA) Analysis
Strategic planning and risk assessment
This paper was a brief overview of some of the work being done in the Department of Defense to leverage XML technologies. The military relies heavily on simulations for training, planning, risk assessment, and system development. In order for these simulations to be interoperable, XML and XML-related tools are being created to support knowledge exchange from one domain to the next. The specific work being done at ARL on the use of narrative as a meta-model for this exchange is reflected in SCML.
[Carroll] Carroll, John M., editor. Scenario-Based Design: Envisioning Work and Technology in System Development, John Wiley and Sons, Inc., New York, 1995.
[Hobbs03Spr] Hobbs, Reginald. Sharing Stories: Using Narrative for Simulation Interoperability, In Proceedings of the 2003 Spring Simulation Interoperability Workshop, Orlando, FL April 2003.
[Hobbs03Fa] Hobbs, Reginald. A Narrative Meta-Model Approach to Bridging M & S and C4I applications, In Proceedings of the 2003 Fall Simulation Interoperability Workshop, Orlando, FL Sep 2003.
[Hobbs00] Hobbs, Reginald. An XML-based Framework for Battle Planning Simulations, In Proceedings of the 2000 Winter Simulation Conference, Orlando, FL, 10-13 December 2000.
[OMT] U.S. Department of Defense. High-level Architecture Object Model Template Specification Version 1.3, Defense Technical Information Center, 20 July 1998.
[OneSAF] Henderson, Christopher. Model Execution in the OneSAF Objective System, In Proceedings of the 2003 Spring Simulation Interoperability Workshop, Orlando, FL April 2003.
[Potts] Potts, Colin, ScenIC: A Strategy for Inquiry-Driven Requirements Determination, RE'99: International Symposium on Requirements Engineering, Limerick, Ireland, IEEE Computer Society Press. 1999.
[Pullen] Pullen, J. Mark. Internet and Multicast Service Issues for XMSF, In Proceedings of the 2003 Spring Simulation Interoperability Workshop, Orlando, FL April 2003.
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