Page 13 - DCAP608_REAL TIME SYSTEMS

Real Time Systems

Notes 8. An OS that can absolutely guarantee a maximum time for the operations it performs is
referred to as hard real-time.
9. Soft real-time systems are designed to absolutely guarantee that a task will execute within
a certain worst-case timeframe.
10. For projects involving safety or systems that could result in a large investment in the
event of failure, hard real-time is often a requirement.
11. Soft real-time systems are designed to satisfy your timing requirements most of the time
but without absolute certainty.

12. Hard real-time systems guarantee (when programmed correctly) that a deadline will be
consistently met, while soft real-time systems may periodically exceed the deadline.

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Case Study Correct Development of Real-time Embedded

Systems in UML

MEGA will develop a methodology and tools for the development of real-time
and embedded systems using UML, based on a clean semantics of the different
Oarchitectural viewpoints and their relations. The aim of the project is to increase
the efficiency and competitiveness of the European software industry by providing tools
improving the quality of software while reducing the expense of the validation phase. The
OMEGA approach to software quality is to use UML for the description of a unique reference
model, from which are derived semantically related models for functional, validation,
performance analysis, as well as implementations; all evolutions are reported in the
reference model for tracking of its influence. A semantically sound component based
development plays an important role, which makes sure that interfaces are sufficient to
guarantee the requirements.
Objectives
OMEGA aims at the definition of a development methodology in UML for embedded and
real-time systems based on formal techniques and used to improve commercially available
UML tools. For this purpose we will identify reasonable and effective subsets of UML for
real-time, as well as necessary extensions. Provide formal foundations, methods and tools
for compositional verification of real-time systems within UML. Construct a development
methodology based on the UML modelling and specification capabilities and the
verification methods and tools developed in the project. Apply industrial case studies for
evaluating the proposed methodology and verification tools. Work description:
To achieve our aim, we will develop results in the following interdependent directions:

1. Modelling and Specification Language: We select a small subset of UML notations
that allow the design of reactive and real-time systems. If needed, we also propose
small extensions. The resulting language contains notations to model the system
under development including both functional and non-functional aspects, and specify
the requirements to be met by the system.
2. Verification and Synthesis: We will adapt and extend existing formal verification
technologies to UML, identify the new needs in verification techniques raised by the
powerful structuring features of UML and develop compositional verification
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