Re-hosting a Constructive Legacy Simulation With Modern Technologies

Transcription

1 e-hosting a Constructive Legacy Simulation With Modern echnologies Leroy A. Jackson Gerald M. Pearman Michael L. McGinnis US Army ADOC Analysis Center PO Box 8692 MONY, CALIFONIA Keywords: Simulation, Simulation Architecture, Computer Generated Forces, Object Oriented Design ABSAC: he US Army raining and Doctrine Command (ADOC) Analysis Center (AC) in Monterey, California is conducting research to re-host a popular, legacy simulation on a new computing platform featuring modern technologies. he project will demonstrate the application of advanced technologies to support development of future simulations, such as Combat XXI, WASIM, and OneSAF. Baseline technologies applied to the legacy model include High Level Architecture (HLA) compliance, an innovative, modular architecture, a detailed object-oriented design, stateof-art user interfaces, and modular terrain. esearch and development of the new system, called HLA Warrior, will produce insights beneficial to development of next generation military simulations. he object-oriented design will facilitate object re-use across simulations, accelerate development times and improve interoperability between models. HLA Warrior s innovative architecture includes advanced event handling, data storage, and distributed capabilities. HLA Warrior's re-configurable user interface will demonstrate use across multiple user domains. Finally, HLA Warrior's modular terrain research will facilitate interoperability between models with dissimilar runtime terrain representations. 1. Introduction During the past year, the US Army raining and Doctrine Command (ADOC) Analysis Center (AC) in Monterey, California began re-hosting a popular, legacy simulation called Janus with modern technologies. Janus is a high-resolution military simulation that currently runs on a Hewlett Packard (HP) workstation running the UNIX operating system. he project will re-host Janus on a personal computer (PC) running the Windows N operating system. his project involves advanced computer simulation technologies such as making the new simulation High Level Architecture (HLA) compliant, designing an innovative, modular system architecture, creating an object-oriented design, using state-of-the-art graphical user interfaces, and designing and implementing a modular terrain component. When complete the simulation, called HLA Warrior, will provide valuable lessons to the modeling and simulation community for the next generation of Army military simulations such as OneSAF, WASIM and Combat XXI. his paper focuses on HLA Warrior s system architecture and highlights expected benefits of the new architecture. 2. Project Goals hree high-level goals of HLA Warrior are to produce a modern, modular, distributed simulation. 2.1 Modern echnologies he HLA Warrior hardware platforms, software applications, and graphical user interface (GUI) conform to the most current commercial standards. he computing power, availability, and cost effectiveness of PCs make them a logical platform for future military simulations. herefore, HLA Warrior is primarily designed for a PC running Windows N. HLA Warrior developers are writing the application using C++, a modern programming language that supports HLA Warrior s object-oriented design. Additionally, HLA Warrior uses Vision XXI, a state-of-the-art commercial GUI that offers many advanced development options including the ability to re-configure the GUI at runtime, define focus sets for display, and rapidly integrate simulation data into after action review (AA) presentations. Finally, HLA Warrior leverages many state-of-the-art Janus software innovations developed during the past decade while applying new, cutting edge methods to define the state-of-the-art software architecture for the next decade. 2.2 System Modularity he HLA Warrior architecture follows a modular approach in the design of high-level system components. For example, the HLA Warrior GUI runs as a separate process distinct from the main HLA Warrior simulation application. HLA Warrior s objectoriented design also promotes modularity in the sense that application domain models are constructed as objects that encapsulate attributes (local state data) and methods (code). he object-oriented design enables future enhancements without requiring major code rewrites and supports reuse among simulations. 2.3 Distributed Applications he system architecture allows different instances of the HLA Warrior model to function on distributed,

2 networked computers integrated through a single internal distribution mechanism. Based on operational requirements, HLA Warrior must also operate in a distributed, interactive mode with other models. HLA Warrior is distributed externally by interoperating with other models using either I approved Distributed Interactive Simulation (DIS) protocols or HLA specifications and rules. 3. HLA Warrior Architecture he HLA Warrior architecture features a high-level software design that bridges the gap between user system requirements and system functionality. he architecture lays out system functionality in a fairly abstract manner without providing specific implementation details. he HLA Warrior Architecture Specification [1] describes major modules and functions, the strategy to integrate command and control modules and functionality, software modules and code that enable re-use, major data structures, key algorithms, major HLA Warrior objects, error detection and processing, robustness considerations, and performance goals. his paper focuses primarily on major HLA Warrior modules and functions. HLA Warrior conforms, in all ways possible, to a loosely coupled, modular design. A module encapsulates a collection of closely related objects and other data or services. he HLA Warrior architecture goal is to provide uniform application programmers interfaces (APIs) between major system partitions and to enforce consistent use of these interfaces across the system to facilitate software maintenance and evolution. Figure 1 illustrates the HLA Warrior architecture. 3.1 Simulation Core he HLA Warrior simulation core is an objectoriented, entity level, discrete event simulation of combined arms combat. he simulation core includes modules and algorithms for all HLA Warrior entities. Janus models combat entities and combat phenomenology using data. In HLA Warrior this data is encapsulated in Warrior classes in the simulation core. 3.2 Simulation Control he HLA Warrior Discrete vent Simulation (DS) ngine controls simulation events by maintaining a set of functionally-oriented priority queues. For instance, a distinct queue may contain all movement events while another queue maintains firing events. he same controller manages system events so that the impact of common, low-level system activities such as network communications and file I/O is considered when executing simulation events. 3.3 HLA Warrior Algorithms HLA Warrior algorithms are adapted from Janus algorithms. he simulation core contains classes derived from Janus combat entities and combat phenomenology. Some aspects of Janus algorithms are directly translated into class methods. For example, the terrain class has a method to determine if line of sight exits between two entities. However, other aspects of Janus algorithms, such as the detection cycle, must be translated into processes that act upon a variety of objects in HLA Warrior. hese processes are the HLA Warrior algorithms. DS Controller Warrior Classes GUI Order ntry xercise Control eplay HLA Warrior apestry API Warrior Modules V U A K P S N L Y N W O K Object Monitors untime Object epository A K P S N L Y S P A S Figure 1. HLA Warrior Architecture Diagram ask & GUI Scripts (Dynamic Warrior Class Development) Algorithms errain API xternal Interfaces Object Database Other Systems HLA DIS C4I

3 3.4 errain Module he HLA Warrior simulation core also includes the terrain module. It encapsulates the representation of surface elevation and terrain features by providing a standard run-time interface for terrain. he terrain interface contains a standard set of terrain services that allow HLA Warrior to use the terrain database independent of the underlying terrain representation. By using this interface, HLA Warrior developers can select different run-time terrain formats without making source code changes. his also minimizes the impact of changing the run-time terrain representation for other components that use the existing set of standard terrain services [2]. 3.5 User Interface he HLA Warrior user interface consists of one or more windows-based GUIs. he GUIs display simulation data for scenario development, order entry, simulation monitoring, analysis, and after action review. HLA Warrior GUI development follows the Model-View-Controller paradigm that isolates the information display from the model containing the information [3]. he GUI is developed using the VU graphics environment. VU provides a high level scripting language for GUI construction. [4] Most of the user interface is defined using scripts. hese scripts are interpreted at runtime allowing the user to dynamically alter the interface during execution. he VU graphics environment and the apestry Kernel development environment are integrated. his simplifies linking the GUI to the simulation. 3.6 apestry Kernel HLA Warrior uses the apestry Kernel [5] to isolate the simulation core from the operating system and hardware. his supports platform independence in a manner similar to the Java Virtual Machine. he apestry Kernel also provides: a scripting environment for class development and management, a direct access dynamic object database, a language parser, and a network communications server. he listener design pattern [5], also referred to as an object monitor, represents one of the most important architecture features of the apestry Kernel. his software design pattern allows objects to register their interest in state changes of other objects and subsequently receive notification of those changes. Passively monitoring and reacting to object state changes in this manner mimics human behavior and relieves an object of the task of knowing in advance all other objects that may be interested in its state. he apestry Kernel also supports run-time inheritance. his means that objects can add new characteristics or attributes during scenario execution. For instance, a user may create and attach a new movement algorithm to an object at run-time to simulate a different movement scheme. 3.7 Distribution Service he HLA Warrior architecture supports various distribution mechanisms through a common distribution service. he distribution service observes entities modeled by the HLA Warrior core and distributes state changes using appropriate protocols. he HLA Warrior distribution service also receives state changes for entities modeled on other systems and updates the runtime object database Internal Distribution As a distributed model, HLA Warrior exchanges class descriptions and object instance data using the apestry Kernel network communication services. he internal distribution mode allows HLA Warrior to run on multiple computers when not interoperating with other models. However, operating with other simulations in a distributed mode requires other mechanisms such as DIS and HLA DIS and HLA HLA Warrior supports both DIS and HLA distribution standards. In distributed interactive simulation environments, models broadcast information in the form of protocol data units (PDUs). HLA Warrior broadcasts and receives entity-state, fire, detonation, and cultural (smoke) PDUs. HLA Warrior also supports pause and resume capabilities in DIS. Simulations conforming to High Level Architecture (HLA) interoperate with other models, called federates, using run-time infrastructure (I) services to subscribe to, distribute, and receive object attributes and interactions. A common federation object model documented in HLA object model template (OM) format defines the content of object classes. HLA Warrior implements a local I component to support HLA interoperability. 3.8 un-ime Object epository HLA Warrior stores all objects in a single run-time object repository. he HLA Warrior simulation core and the distribution service create, update and destroy objects stored in the repository using apestry Kernel services. ach state change and method invocation is recorded for each object in a database to support playback and recovery. 4. Architecture Benefits he HLA Warrior architecture offers unique capabilities to the combat modeler. hree specific areas where modelers will benefit from HLA Warrior architecture technology include rapid prototyping, dynamically defined objects, and attaching object observers.

4 4.1 apid Prototyping ight development timelines and limited resources require HLA Warrior developers to apply rapid prototyping techniques. he HLA Warrior architecture provides a development environment that satisfies these requirements. he apestry Kernel development environment allows code writers to develop classes and algorithms using a scripting language. hese scripts can invoked directly from the user interface. his powerful, time saving technique relieves the code writer from the burden of recompiling source code to observe the results. Once invoked, the code writer can immediately verify intended object behavior from model output. he debugged script can subsequently be replaced by compiled code. he development environment also permits independent GUI and source code development without the lengthy process of defining the numerous protocols required for reliable model-interface interaction. he apestry Kernel, integrated with the VU graphics environment, makes it easy to construct GUI screens that depict developed classes and algorithms. he kernel maintains all classes in a manner that allows developers to seamlessly browse classes, identify class attributes, and determine relationships among objects. With this knowledge, GUI developers can build an HLA Warrior interface guaranteed to accurately represent object functions without pre-defining interface protocols. 4.2 Dynamically Defined Objects apestry Kernel services include creating, deleting, manipulating, and observing objects. Using the kernel, tasks can be defined as either a set of code-based procedures or a scripted set of tasks. Scripted tasks can be defined or modified at run time allowing dynamic object behavior. For instance, a developer may assign an object an alternate movement algorithm during the scenario without halting execution to write source code and recompile. Dynamically defining objects is revolutionary in the sense that it significantly enhances model flexibility and eliminates costly, time-consuming code re-writes. his concept also eliminates the need to be 100% correct about class definitions and functional content during initial class development. his concept also extends to GUI development, permitting users to customize interfaces at run-time. econfigurable GUIs are necessary because both trainers and analysts will use HLA Warrior, each requiring different tools to accomplish assigned tasks and because the HLA Warrior user interface will evolve over time. 4.3 Attaching Object Observers he HLA Warrior run-time environment allows users to attach observers to object instances for monitoring object state and method invocation. Observers are notified when their observer criteria are satisfied by a change in state or a method invocation on the object instance under observation. In this paradigm, observers become responsible for invoking appropriate tasks. he programming environment allows for a single instance of an object to have multiple observers so that a single state change may result in the execution of multiple tasks. Attaching passive observers to objects is analogous to a human observing his environment and reacting to changes. his observation-based approach also parallels behavior patterns for entities in Semi- Automated Forces (SAF) simulations. 5. Conclusions he HLA Warrior project provides developers of future simulations with unique lessons for rapidly transforming legacy models into modern, state-of-theart simulations. ransforming a simulation involves innovative, rapid prototyping techniques provided by HLA Warrior s development environment. Additionally, the architecture fully supports dynamic change to both the simulation application and GUI, enabling maximum growth and flexibility with minimal cost. his development paradigm will serve as a case study for rapid, cost effective fielding of future simulations. eferences 1. Jackson, L. A. (1997), he HLA Warrior Architecture Specification, U.S. Army AC- Monterey echnical eport, Monterey, CA. 2. Jackson, L. A., S. Pratt and D. Henderson (1999), A Modular errain Component Interface For Computer Generated Forces, proceedings of the 1999 Simulation echnology and raining Conference. 3. Gamma,.,. Helm,. Johnson and J. Vlissides (1995), Design Patterns: lements of eusable Object-Oriented Software, Addison-Wesley. 4. apestry Solutions (1995), VU Introduction and utorial. 5. apestry Solutions (1998), apestry Kernel eference Guide. 6. Jacobson, I., M. Christerson, P. Jonsson and G. Overgaard (1995), Object-Oriented Software ngineering: A Use Case Driven Approach, Addison-Wesley. Author Biographies Major Leroy A. Jackson is a U.S. Army officer with over twenty years of enlisted and commissioned service. He graduated with a BA in Mathematics from Cameron University in 1990 and with an MS in Operations esearch from the Naval Postgraduate School in Major Jackson is a recipient of the US Army Chief of Staff s Award for xcellence in Operation esearch. He is currently an operations research analyst at the U.S. Army raining and Doctrine Command (ADOC) Analysis Center (AC) in Monterey, California and continues

5 graduate studies in operations research at the Naval Postgraduate School. Major Gerald M. Pearman is an Army officer with over twelve years of commissioned service. He graduated from the United States Military Academy at West Point in 1986 and was commissioned in the Aviation branch. He completed an MS in Operations esearch from the Naval Postgraduate School in He is currently an operations research analyst at the U.S. Army raining and Doctrine Command (ADOC) Analysis Center (AC) in Monterey, California and heads the HLA Warrior project. Lieutenant Colonel Michael L. McGinnis is an Army officer with over twenty-two years of commissioned service. He graduated from the United States Military Academy at West Point in He received MS degrees in Operations esearch and Applied Mathematics from the enesselaer Polytechnic Institute in 1986 and a Ph.D. from the University of Arizona in He is a Distinguished Graduate of the Naval War College and a isk Prize winner. LC McGinnis currently serves as the director of the U.S. Army raining and Doctrine Command (ADOC) Analysis Center (AC) in Monterey, California.