Industry Standards

DIS

DIS, or Distributed Interactive Simulation, is a standard networking protocol for exchanging information among various simulation applications. It defines a set of Protocol Data Units, or PDUs, for publishing Entity State information, Fire and Detonate events, Logistics information, Emissions and Communications data, and more. The DIS protocol was defined through an open standards development process, with participation by government, industry, and academia.

The DIS protocol first became an IEEE Standard in 1995, under the official name IEEE 1278.1-1995. In 1998, an addendum to the DIS Standard was published, expanding DIS to include new PDUs for Aggregates, Environmental Features, Minefield, and more. The addendum is also an IEEE Standard, known as IEEE 1278.1a-1998. Since IEEE owns the copyright on the DIS Standard, copies of the Standard may be obtained only from IEEE. The IEEE product code for IEEE 1278.1-1995 is SH94351, while the product code for 1278.1A-1998 is SH94604.

While the IEEE DIS Standards contain all of the information about the structure of the various DIS PDUs, the values for the various DIS enumerations were deemed too dynamic, or fast-changing to include in a slow-changing IEEE Standard. For example, new weapons systems are introduced from time to time, new radio encodings are developed, and even names of countries can change. For this reason, these values and enumerations are maintained by SISO (Simulation Interoperability Standards Organization) in a separate document called Enumeration and Bit Encoded Values for Use with Protocols for Distributed Interactive Simulation Applications. This document is available from the SISO web site. As of early 2006, the URL for the most recent version can be downloaded from the SISO website using this link: SISO-REF-010-2005.zip

Links to past and future versions can be found at: http://www.sisostds.org/index.php?tg=articles&idx=More&article=40&topics=18

HLA

The HLA (High Level Architecture) is a more recent standard for interoperability among simulations. Rather than a networking protocol (wire standard) like DIS, HLA defines an architecture with a set of API (Application Programmer's Interface) Standards. Simulation applications (known as federates in HLA) communicate by making calls to the HLA APIs. A piece of software known as the RTI (Run-time Infrastructure) implements the HLA API, and is responsible for transporting data from one federate to another. Like DIS, the HLA Standards are owned by IEEE. There are three documents that comprise the HLA Standard, all available from IEEE.

IEEE 1516-2000 - IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA) - Framework and Rules provides the rules and definitions for implementing and using HLA. Its IEEE product code is SH94882.

IEEE 1516.1-2000 - IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA) - Federate Interface Specification defines the various services provided by an HLA RTI, and contains the APIs. Its IEEE product code is SH94883.

IEEE 1516.2-2000 - IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA) - Object Model Template (OMT) Specification defines the format used for describing object models in HLA. An object model dictates what kinds of data a particular set of HLA federates will be exchanging. The IEEE product code for this document is SH94884.

There is a fourth document that is not technically part of the definition of HLA, but that defines some of the recommended practices for using HLA. It is called IEEE 1516.3-2003 - IEEE Recommended Practice for High Level Architecture (HLA) Federation Development and Execution Process (FEDEP), and its IEEE product code is SH95088.

While the IEEE 1516 series of standards represents the "current" version of HLA, many HLA simulations are still using an earlier version of HLA known as HLA 1.3. This version was maintained by DMSO and the US DoD prior to IEEE Standardization. According to the DMSO web site, requests for copies of the HLA 1.3 Specification may be sent to

The documents that make up the HLA 1.3 specifications are as follows:

HLA Interface Specification Annex D: Java API
HLA Interface Specification Annex C: Ada 95 API
HLA Interface Specification Annex B: C++ API
HLA Interface Specification Annex A: IDL API
HLA Interface Specification Version 1.3
HLA Object Model Template Specification (Version 1.3)
HLA Rules (Version 1.3)

RPR FOM

While the HLA Standards dictate how federates exchange data, it is a FOM (Federation Object Model) that dictates what data is being exchanged in a particular federation. HLA does not mandate the use of any particular FOM, however, several "reference FOMs" have been developed to promote a-priori interoperability. That is, in order to communicate, a set of federates must agree on a common FOM (among other things), and reference FOMs provide ready made FOMs that are supported by a wide variety of tools and federates. Reference FOMs can be used as-is, or can be extended to add new simulation concepts that are specific to a particular federation or simulation domain.

The RPR FOM (Real-time Platform-level Reference FOM) is a reference FOM that defines HLA classes, attributes and parameters that are appropriate for real-time, platform-level simulations. Applications that have previously used DIS (or would have considered using DIS), often use the RPR FOM (or a derivative of it) when they playing in an HLA world. The RPR FOM was developed by a SISO Product Development Group (PDG). Its goal was not to just implement the DIS PDU structures within HLA object and interaction classes, but rather to provide an intelligent translation of the concepts used in DIS to an HLA environment.

RPR FOM 1.0 became a SISO Standard in 1999, under the name SISO-STD-001.1-1999. A companion document, known as the GRIM (Guidance, Rationale, and Interoperability Mappings) provides documentation for the RPR FOM. This document is known as SISO-STD-001-1999. Both documents may be found on the SISO web site at: SISO_CID_59

RPR FOM 1.0 is based on the IEEE 1278.1-1995 version of the DIS Standard. RPR FOM 2.0, based on the IEEE 1278.1a-1998 addendum is nearing approval as a SISO Standard.

The current drafts of the FOM and GRIM can be found at:
SISO Products & SISO Standards RPR-FOMV1.0_Final.pdf
SISO Products & SISO Standards GRIM_RPR-FOM_1-0v2.pdf

DLC API

The version of the C++ API for HLA that was defined by IEEE 1516.1-2000 does not support Dynamic-Link Compatibility among RTI implementations. That is, it is not possible for a federation to switch from one RTI implementation to another without recompiling federates. This limitation is more serious than it sounds, because it takes the choice of which RTI to support out of the hands of the end-user. The program manager for a federation must convince federate providers and tool vendors to build specifically for the RTI he chooses.

The Dynamic Link Compatible (DLC) HLA API was developed to solve this problem with the original IEEE 1516 specification. The DLC API lowers the barrier to reuse, i.e. more easily supports the idea of reusing federation in various federates using different RTI implementations. The DLC API is a recently approved set of SISO Standards. The DLC API for HLA 1.3 is known as SISO-STD-004-2004, while the DLC API for IEEE 1516 is known as SISO-STD-004.1-2004. Visit SISOs website for more information.

The actual C++ and Java APIs that are included as Appendices to the SISO DLC Standards are also available for download at: ftp://ftp.mak.com/out/Final_DLC_APIs.zip

The module names are:

RTI_API_C++1.3
RTI_API_C++1516
RTI_API_JAVA_1.3
RTI_API_JAVA_1516