Simulation Exercise Control of Heterogeneous Assets Using a Web Service Interface Template

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Simulation Exercise Control of Heterogeneous
AssetsUsing a Web Service Interface Template
2005 FALL SIW

• Raytheon Technical Services Company LLC
• Stanley Allen
• September 21, 2005

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Introduction
Modern simulation exercises are often built with
legacy simulation elements that have been
constructed using a variety of technologies and
interfaces. The use of Distributed Interactive
Simulation (DIS) and High Level Architecture
(HLA) standards has promoted the ability to allow
such assets to communicate with one another and
to be federated together.
In spite of these advances, exercise control is
still problematic because data communication is
only part of the problem. Other issues that must
be addressed are managing the orderly startup
and shutdown of the assets, controlling exercises
with multiple HLA federations, introducing
effective exercise states (e.g., run vs. pause),
and incorporating and controlling peripheral
applications.
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Background
We present a system, ExCon (Exercise Control),
which addresses these issues. A template is
defined with operations to provide a common
control interface to each asset. Assets
instantiate the template and implement a web
service based on it.
The asset interface allows remote, automated
control and commanding of the assets. In the
implementation, the web service may use scripts
or other techniques to control asset execution
and to pass ExCon-defined or asset-specific
commands to the underlying asset.
The control software is composed of a web
application with server software and a browser
applet. The browser interface permits a user to
view and control exercises the server houses
the central controller that invokes the assets'
web services and maintains exercise state.
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Exercise Control Overview

• Exercise Control (ExCon) provides centralized
  management of exercises
• An exercise is comprised of assets which are
  packaged as web services
• ExCon manages state, execution, time, status, and
  moding of each asset
• What can be wrapped as an asset?
• Legacy executables/simulations
• COTS products
• HLA federates and RTI executives
• Web services
• Subroutine libraries
• Hardware elements
• Open software solution
• Standard interfaces (HTML, XML, WSDL, SOAP, J2EE,
  JSP)
• Use of free licenses
• Platform-, operating system-, and language-
  independence for assets
• Asset interface hooks permit tailored
  configuration and commanding of an asset to
  substitute for console operation
• One Button (scripted) control of exercise/asset
  functions, full automation

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ExCon Architecture
HW I/F
INTRANET
Service
Application
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ExCon Software Elements

• ExCon server software
• Control software written in Java
• Has interfaces to web page and assets
• Implemented as a web application (JSP) and web
  service (WSDL)
• Server to the web page client to the assets
• Maintains exercise state and user (web client)
  files
• Asset Web Service shell
• Resides on each asset node, packaged as web
  service
• Interface expressed as WSDL interface, standard
  tools generate Java shell
• Asset owners responsible for implementing the
  asset interface shell on their platforms and
  deploying the web service
• ExCon web site
• Exercise Control Applet is divided into three
  major sections
• Master control display and menu bar,
  Configuration, Status
• Exercise and File Management Links
• Create, select, remove, script exercise Manage
  user/exercise/asset files.

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ExCon Display

• Web site navigation links in left frame
• ExCon GUI applet in right frame
• Main Menu bar for exercise control
• Asset Control menu allows assets to be marked
  made part of an exercise
• Clicking on an asset icon pops up a menu of asset
  commands
• User can configure, command, and perform file
  transfers, as well as start/stop/abort execution
  for assets in Assets In Exercise panel
• The Status Panel shows status logs from each
  Asset
• Executing assets green icon, Idle assets amber
  icon

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ExCon Display

• A view of the status/state/mode of each asset in
  the ExCon Servers master asset list

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Asset States and Modes
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Health and Status

• The controller implements a document-style web
  service to receive status from the assets. Assets
  produce three types command status, health
  status, and logged status.
• Command status is reported when an exception is
  not generated from the asset interface
• Generally success status is sent at the end of
  command processing
• Some commands may take a non-trivial amount of
  time to process. In these cases, the asset owner
  may decide to return a command status of
  pending until the operation is complete, and
  success upon completion.
• Health status asset hardware/software health
• The asset sends ok status once every 15-20
  seconds. If the controller does not receive ok
  status after a few minutes, the asset is probably
  unreachable.
• Logged status application-specific status
• Passed to the user and put into a status log file
• Each log has a unique ID (asset ID number)
• Status log messages are flagged with severity
  indicator
• The ID and severity indicator allow the web user
  to squash chatty feedback

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Time Management

• Each asset maintains GMT as a wall-clock time
• Each asset is expected to retrieve the current
  GMT (e.g., via NTP)
• The simulation time is known as Simulated GMT
  (SGMT)
• The ExCon server sends out global SGMT to each
  asset at the beginning of execution
• The user can enter an SGMT factor (multiplier)
  for faster than real time or slower than real
  time operation
• Each asset is responsible for maintaining its
  picture of SGMT based on the initial SGMT,
  ongoing GMT, and the SGMT factor

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Exercise Modes

• There are four exercise modes
• PAUSE, RUN, SNAPSHOT, INITIALIZE
• While the exercise is in a certain mode, all of
  the assets in that exercise must be in that mode.
  So, when the user changes the mode of the
  exercise from RUN to PAUSE, all of the assets
  will be commanded to go to PAUSE by the ExCon
  Server.
• In addition to normal (ASAP) RUN/PAUSE commands,
  the web/GUI interface to the exercise offers
  commands to effect a RUN transition at specified
  GMT time and a PAUSE transition at specified SGMT
  time.

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HLA Control

• An HLA federate is treated as an asset, wrapped
  with the asset interface
• The interface has two functions,
  joinHLAFederation and resignHLAFederation
• The asset will make use of uploaded files,
  default files, or the selected configuration to
  properly join the federation
• Joining and resigning HLA federations are done on
  a per-asset basis the exercise itself does not
  join a federation
• More than one federation can be in the exercise
  at a time different assets in the exercise may
  belong to different federations
• The DMSO RTI executive is wrapped as an asset,
  and can be started/stopped/commanded via the GUI
  interface

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Data Logging

• The asset can provide data id strings for
  retrievable data items
• Must be unique within the asset
• An asset can provide a data logging capability
• The asset will capture and save data logs with
  timestamps with data ids
• Results available via file retrieval
• User can suspend and resume data logging
• Current interface supports only one data log
  capture at a time
• An asset can provide a query capability for the
  latest value of data items using data ids
• This could be used to view data at run time

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File Management

• Files can be uploaded or retrieved to/from the
  asset
• The controller is the uploading and retrieving
  client
• Files can be uploaded to the users account on
  the ExCon server from here they will be uploaded
  to the asset
• The asset should define upload and retrieval
  areas for files
• Simple file model
• Each file is identified by a string name
• A file is made up of an array of strings
• Controller retrieves files as ASCII text and
  saves them to the users ExCon server directory.
  Then the user can download them from the server.
• The asset is responsible for directories this is
  hidden from the ExCon user (avoids asset
  directory management issues)

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Asset-specific commanding

• The asset can define commands to expose to the
  user
• The commands are provided as a list of strings
• Each command has a text description
• For each command, any number of parameters are
  permitted
• Also provided as a list of strings with
  descriptions
• On the applet, the user selects from the list of
  commands, views the command and parameters
  descriptions, and enters the parameters as string
  values
• The asset will attempt to execute the command and
  can return results in the form of an array of
  strings
• The asset may provide variant command lists
• For example, one list before execution, another
  once it starts up

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Scripting

• ExCon supports a simple script mechanism so
  that exercise
• control can be programmed
• Written in an ExCon-defined language
• Each GUI action can be coded as a script
  statement
• Interpreted and executed on the ExCon Server
• Allows branching based on command result
  (success, warning, etc.)
• SLEEP statement indefinitely or for a number of
  seconds
• Script can issue logs to the status window
• Script control from the browser applet
• Upload script files, start execution
• Pause and resume execution
• Resume execution for a script that has put
  itself to sleep
• Allows for manual control of assets when
  necessary
• Indicator on GUI tells whether the script is
  executing or sleeping
• Terminate script execution at any point

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Conclusions

• Deployment and use
• Used for a variety of internal applications and
  exercises
• Assets include HLA RTIs, federates, standalone
  apps, web services, gateways
• Lessons learned
• A WSDL template provides consistency for the
  client
• Free technologies seem to be robust enough
• Planned enhancements
• Security
• Platform commanding
• Dynamic asset discovery (currently using flat
  file)