Key Interoperability Technologies

How long does it take to migrate a federate written for HLA 1.3 to the current IEEE 1516 HLA standard? This page provides some tools to estimate the amount of work as well as some practical advice.

What do you need?

First of all you need a complete and certified RTI for the HLA IEEE 1516 standard. If your FOM is not already available in the HLA 1516 format you will also need an OMT (HLA object modelling) tool that can assist you in converting the FOM.

In addition you of course need the source code for the federate and a developer that is familiar with the federate. A reasonable knowledge of HLA 1.3 is also assumed, at least of the functionality that is used in the federate.

There are a number of documents that are highly recommended:

• The IEEE 1516 standard itself can be acquired from IEEE directly. See IEEE

• There are two porting guides that describe what a number of fundamental HLA calls look like in the HLA 1.3 standard and what they look like in HLA 1516. There is one guide for C++ developers and one for Java developers. See Pitch pRTI 1516 Support

• There are also papers published with experiences, guidelines and code snippets available from SISO. See SISO. Some examples are: "Experiences Using the Six Services of the IEEE 1516.1 Specification: A 1516 Tutorial" (04S-SIW-056) and "A Practical Guide to Implementing a Biomedical Federation Using the 1516 RTI with the C++ Interface" (03F-SIW-098).

• You can also download sample federates like the "chat" federate that comes with pRTI 1516 LE or the "RTIperf" federate, both of them available for free from Pitch web site. Download.

There are also additional resources: HLA 1516 hands-on training is readily available in Europe from Pitch and in North America from AEgis. HLA 1516 consulting is also available.

Estimating migration time

If you need to convert the FOM this will typically take 1-3 days. Be sure to take advantage of the more complete object model which now also contains detailed data types. Remember that the old HLA 1.3 MOM will need to be replaced by the new HLA 1516 FOM

The major work is the migration of the federate. Assuming that the developer is well familiar with the federate source code and the development environment, the major factors are:

1. How much of the HLA functionality is used and how complex is the usage. Are only federation, declaration, object and time management used (and in a straight forward way)? Are ownership or DDM used? Are they called from many places in the federate?

2. What development language is used? Refactoring and debugging will probably be considerably easier in a Java environment with state-of-the-art tools as compard to C++.

3. Is this a conventional federate or is it a complex HLA tool that processes FOM or MOM data?

4. What level of integration test and VV&A needs to be done?

The following diagram can be used for the time estimation. Each bar shows a minimum and a maximum time. The migration including basic testing but excluding integration testing and VV&A will normally take between 2 and 8 man-weeks.

This diagram is based on a number of real migration cases. Here are some of them:

• A US Medical federation migrated three federates from HLA 1.3 to 1516 (C++), each took two man-weeks.

• A European sensor model migrated the federate from HLA 1.3 to 1516 (C++) in one man-week

• A European CGF and Flight simulator created a new, generalized HLA 1.3 and 1516 module, four to eight man-weeks

• The "Test Federate" (from the F. Kuhl HLA book) that contains all RTI calls (Java), was migrated in one man-week (by a student)

• A US organization studied HLA 1516 for five weeks and then migrated a number of federates in two man-weeks per federate

• A general simulation-building tool that reads FOM and generates simulation and HLA code migrated in four man-weeks

• Another general simulation building tool that reads FOM, generates simulation and HLA code migrated in six man-weeks