EuroFighter - Mitigating Requirement Obsolescence

Our Client, BAE Systems, have been responsible for the development of the Eurofighter Typhoon fuel computer system since the Eurofighter Typhoon project commenced. Until recently, the fuel computer team have adhered to the original Eurofighter development process which relied upon the CoRE methodology and bespoke toolset for requirements specification.

In 2010 it was decided that the CoRE process was inefficient and one of the primary causes for BAE Systems dissatisfaction in the cost and length of time that was being taken to incorporate changes into each capability. It was also recognised that it was becoming increasingly difficult to find engineers who were available and experienced in the use of the CoRE method and toolset.

In order to address these problems it was decided to migrate the requirements into a standard modelling notation (UML), supported by a COTS toolset. The aim was to achieve the migration of the existing CoRE requirements into the new UML toolset with the aid of an automated tool. Naturally this automated migration avoided errors that would have occurred through a manual process and helped to reduce costs. Concurrently, it was also necessary to retrain project members in UML and the Studio toolset skills.

The migration activity started in March 2011 and was undertaken in an incremental fashion to reduce the risk of a significant impact to the on-going Eurofighter Typhoon development work. The migration activity was completed at the end of 2011.

In the late 1970s BAE Systems developed Controlled Requirements Expression (CoRE) in order to remove the ambiguity introduced when requirements are specified using text. CoRE was subsequently used to capture the requirements on a number of military software intensive systems to ensure that they were unambiguous. However, over the last 10 years, CoRE has been less widely adopted due to its proprietary nature, its limited ability to represent dynamic behaviour and its lack of integration with any design toolsets. CoRE is also a notation for modelling the requirements of functionally decomposed software and as such is now almost obsolete as the majority of software developed today is object oriented.

Hierarchical Object Oriented Design (HOOD) was based upon early work carried out with Abstract Machines (AM) and Object Oriented Design (OOD). This work was performed under contract to the European Space Agency by two French Companies, Matra-Espace and CISI-Ingenierie, with the aim of supporting the development of large, real-time, safety-critical systems. HOOD evolved into a design methodology that concentrated on the best practices of software engineering of the day, namely the HOOD paradigm with the concept of hierarchy. It is a mature graphical and textual methodology, based on an iterative process that emphasises the step-wise refinement of a design model. However, HOOD supports object based rather than object oriented design and it does not support the more powerful object oriented concepts such as inheritance and polymorphism. In addition, the several CASE tools that do support the method did not extend its support to any other language other than Ada83. CoRE and HOOD are supported by toolsets which are hosted on different platforms and which therefore do not integrate.

The CoRE migration process implements an approach in which a UML profile is defined to represent the legacy CoRE elements in a UML modelling environment. This profile also contains ergonomics (menus, toolbars,etc) which replicate the features available in the CoRE tool. The use of ergonomic features provides a mechanism by which tools can be customised in order to simplify the adoption of model based technologies.

The project’s strategy was to:

  • Adopt a model-centric development based on the OMG UML and SysML standards.
  • Develop a bespoke tool to automatically perform the migration to eliminate human error.
  • Extend the UML standard (profiles) to include concepts of domains (CoRE, HOOD, Ada) whilst ensuring greater rigour to minimise errors early in the development.
  • Develop customisations of UML COTS tools to provide the engineers with a familiar modelling environment to maintain and develop the model.
  • Take small steps to integrate the models into the process or re-engineer the system to respond to change more effectively.

Objektum Modernization’s Document Explorer and Legacy Bridge technologies were employed to analyse the CoRE requirement and automatically generate a UML model in Artisan Studio utilising a bespoke CoRE profile.

To demonstrate the feasibility, a test case was devised to cover all aspects of the CoRE standard and used to demonstrate the migration capability.

By adopting a modern, model based development approach the Typhoon UCS project has experienced the following benefits:

  • The mitigation of obsolete CoRE techniques, tools and skills through the use of modern technology such as UML/SysML and Artisan Studio
  • Reduction in risk and cost associated with manual migration through the use of automation to translate from CoRE and HOOD to UML.
  • Improved communication across projects and companies through the adoption of industry standard notations – UML and SysML.
  • Development of a CoRE and HOOD to SysML/UML migration strategy which is repeatable and reusable across projects.
  • Improved traceability through the use of a single model in UML/SysML for both requirements and design.
  • Increased flexibility of engineering resource through use of a common UML/SysML notation for both requirements and design.
  • The CoRE meta-model allows automatic correction of errors and inconsistencies in the existing CoRE requirements during the migration process.
  • The transition to Artisan Studio, which provides good support for ergonomic profiling, increases productivity through automation whilst ensuring quality is maintained through the use of predefined rules.
  • The adoption of UML, a standard notation which decoupled the project from a specific modelling tool, i.e. CoRE.
  • Once developed the CoRE UML profile can be reused across all projects which migrate from legacy CoRE requirements to UML.

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