Ghaith Haddad

The design of SafeJML, a specification language for SCJ with support for WCET specification

Safety-Critical Java (SCJ) is a dialect of Java that allows programmers to implement safety-critical systems, such as software to control airplanes, medical devices, and nuclear power plants. SafeJML extends the Java Modeling Language (JML) to allow specification and checking of both functional and timing constraints for SCJ programs. When our design of the SafeJML is implemented, it will help check the correctness of detailed designs, including timing for real-time systems written in SCJ.

Challenge benchmarks for verification of real-time programs

Real-time systems, and in particular safety-critical systems, are a rich source of challenges for the program verification community as software errors can have catastrophic consequences. Unfortunately, it is nearly impossible to find representative safety-critical programs in the public domain. This has been significant impediment to research in the field, as it is very difficult to validate new ideas or techniques experimentally. This paper presents open challenges for verification of real-time systems in the context of the Real-time Specification for Java. But, our main contribution is a family of programs, called CDx, which we present as an open source benchmark for the verification community.

Specifying subtypes in SCJ programs

Modular reasoning about programs that use subtypes requires that an overriding method in a subtype obeys the specifications of all methods that it overrides. For example, if method m is specified in a supertype T to take at most 42 nanoseconds to execute, then m cannot take more than 42 nanoseconds to execute in any subtype of T. Subtyping is an important aid to maintenance of programs, since it allows one to write polymorphic code (reducing code size and increasing reuse), and allows for convenient extension and enhancement of programs, all of which could be very useful in real-time programming. In this paper we show how to specify timing constraints for subtypes in a way that: permits modular reasoning about timing constraints, supports subtype polymorphism and object-oriented design patterns, and still permits precise reasoning about execution times. This technique supports object-oriented coding and design patterns based on subtype polymorphism, with all their maintenance advantages, to be used in real-time software.

Specifying subtypes in Safety Critical Java programs

Real‐time and safety‐critical code could benefit from the use of design patterns and frameworks that rely on subtyping and dynamic dispatch. However, modular reasoning about programs that use subtypes requires that each overriding method obeys the specifications of all methods that it overrides. For example, if method scale is specified in a supertype Vector2d to take at most 42 ns to execute, then an override of scale cannot take more than 42 ns to execute in any subtype, such as Vector3d. The problem is that subtype objects typically contain more information, such as the z coordinate in Vector3d, and thus their methods often require more time to execute than the methods they override. In this paper, we show how to specify timing constraints for subtypes in a way that both allows overriding subtype methods to have more time to execute and yet permits precise modular verification and checking of timing constraints. Our techniques allow object‐oriented coding and design patterns based on subtype polymorphism to be used in real‐time and safety‐critical software. Copyright

Challenge benchmarks for verification of real-time programs: (abstract only)

Real-time systems, and in particular safety-critical systems, are a rich source of challenges for the program verification community as software errors can have catastrophic consequences. Unfortunately, it is nearly impossible to find representative safety-critical programs in the public domain. This has been significant impediment to research in the field, as it is very difficult to validate new ideas or techniques experimentally. This paper presents open challenges for verification of real-time systems in the context of the Real-time Specification for Java. But, our main contribution is a family of programs, called CDx, which we present as an open source benchmark for the verification community.

DSASim: A Simulation Framework for Dynamic Spectrum Allocation

The current methodology for distributing the frequency spectrum among users is in need of revamping. This is necessary in order to increase the number of users able to access the communication channels; to better manage usage in metropolitan areas, where the usage of wireless communication is still rapidly increasing; and to ensure adequate frequency allocation for users during peak usage times. Several methods and paradigms have been suggested as replacements for the current scheme of distributing spectrum among users. This paper proposes a simulation framework to simulate a broker-based system to implement a dynamic spectrum allocation environment. The broker operates based upon pre-defined spatial and temporal requirements in a manner where operational parameters are set up or collected dynamically. The broker system responds to the radio devices, allocating the suitable amount of frequency spectrum required for a particular application. The results of the simulations show a promising and efficient utilization of frequency spectrum resources.