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Realtime talk: an object-oriented language for hard real-time systems
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009
Abstracts
DIMOS: Distributed Monitoring System from Specification to Delivery, the Realization of a Nuclear Power Plant Supervision System using HOOD and ADA P. Jacobs, D. Pluvinage, pp 61-66
To meet the needs of nuclear power plant supervision, a new generation of computer systems, DIMOS, has been developed. A first installation, completed in 1991, now supervises two production units. A major challenge was the choice of a distributed exmfiguration including 15 computers around a double Ethemet LAN, running either VAX/VMS or VAXELN. The postpartitioned design ensures that the code is independent of the distribution. The structured analysis of user requirements was performed using the YOURDON methodology. The design was unplemented using a Hierarchical Object Oriented Design (HOOD) ease tool, from which the large amount of ADA code was generated.
014
This paper presents a mode-change protocol and an approach to fault recovery in hard real-time systems in Ada. The mode change implementation uses standard Ada, although dynamic priority setting is .required. This assures data consistency and deadline meeting, during the mode change protocol. Fault recovery is based on recovery groups of related processes with a common fault-recovery behaviour. When any process fails, the other processes in the group end their execution and a recovery process, m charge of executing the recovery actions, starts. Those features have been successfully implemented and tested as part of a reusable tasking executive intended to develop hard real-time systems in Ada.
015 010
Implementing Mode Changes and Fault Recovery for Hard Real-time Systems in Ada A. Alcmso, J. de la Puente, pp 95-100
Specification of Real Time Systems for Protection Tasks in Automated High-speed Transportation Systems K. Jopke, R. Knigge, E. Sobnieder, pp 67-74
Towards an Environment for Complex Real Time Control Systems Developing A. Garcia, A. Crespo, pp 101-106
The Ward and Mellor system design method is used to describe the functional behaviour of the control and protection system of a high-speed maglev train. A simulation has already been run successfully. A substantial problem is to obtain the proof of the Automatic Train Protection of the whole system on the functional level. The implementation model which contains the functional behaviour is the only object which can he tested against the program code by the experts verifying the system, who need a dearly structured specification to understand the relations between the program code and the model; in particular, the real-time aspect, and guidelines to interpret the system description.
Real-ume and expert systems provide a general framework to solve a great number of problems not completely solved by means of traditional approaches, for example, the control of complex systems. However, in integrating these techniques, some important problems remain. In this paper a new software architecture is proposed. A server task dealing with all the intelligent activities is defined. Critical tasks are extemal to this server and their deadlines are statically guaranteed using the rate monotonic theory. Intelligent activities are organized as internal tasks with multiple versions. An algorithm is presented to select the most-appropriate versions in order to obtain the best quality response.
011
016
A Visual Real.time Programming Language* K. Bastlaens, J.M. Van Campenhout, pp 75-79
Ada Gets Groomed for the Whole Spectrum of Realtime Duties M. Goblin, F J . A . Gielen, pp 107-112
Among the steps taken to tackle the problem of software engineering for real-time applications was the introduction of visual languages. These have the potential to ease programming as they are more expressive than the conventional textual languages. In the domain of real-time applications, the use of visual languages is mainly restricted to software design languages. Automatic code generators are used to generate a code skeleton, which is filled in with fairly "coarse-grained" hand-written textual program fragments. This paper presents a method to extend existing visual design languages to visual programming languages with a much more powerful visual component. 012
One of the specific areas addressed by the AdA-9X revision team deals with requirements posed by real-time applications and introduces a new building block for real-time Ada: the protected record. This provides a low-level data-oriented synchronization mechanism and a primary support for real-time systems. It can be used to program solutions for real-time problems such as mutual exclusion, conditionally shared data, counting semaphores and signals. This paper compares two approaches for the solution of the classical real-time problem of conditional critical regions, using respectively Ada83 tasking and Ada9X protected records. Runtime support and some implementation issues for protected records on muhiprocessor target systems are discussed.
ReaITimeTalk: an Object-Oriented Language for Hard
Real-time Systems E. Brorsson, C. Eriksson, J. Gustafsson, pp 81-86 This paper describes a real-time language which supports both real-time and behavioural modelling, the object-oriented language RealTimeTalk (RTT), based on the well known Smalhalk paradigm. T h e simple syntax of Smalltalk makes it easier to add and restrict features in the language, and provides for the notion of building applications by components. The environment supports design through frameworks, glvang a well-designed and thoroughly tested base for a certain application domain, and also implying a specific design policy. The overall goals of the RTT project are thus to simplify the modelling of real-time systems and in these types of systems to include predictability and determinism. 013
IPRESPS - A Programming Environment for
017
Defining the Semantics of Languages for Programmable Controllers with Synchronous Processes* L. Marc~ P. Le Pare, pp 113-118
Real-tune systems are systems which interact permanently with their environment by receiving external information and producing output commands on it. They are commonly met in factories for the control of industrial processes. In this case, they are often implemented with Programmable Controllers (PCs). The GRAFCET language, which is derived from Petri-Nets, is often used for programming such PCs. Unfortunately, it is not based on a single semantics, which complicates program verification, program exchange and program simulation. We have expressed its semantics with synchronous processes, implemented them with the synchronous language SIGNAL, and investigated methods to make proofs on it.
Partitioning and S.cheduling of Time Critical Tasks M. Ojster~ek, V. Zumer, pp 87-93 An integrated programming environment, IPRESPS, has been developed for static partitioning of time-critical tasks into concurrent modules and for scheduling those modules for the shortest possible execution time on a model of a macro datafiow computer (MMDFC). IPRESPS has modules for program graph generation, partitioning, memory allocation, code generation, and simulation. A time-critical task is transformed into a fine-grained program graph, then into a near-optimal-grained graph. Node size is determined, and nodes are scheduled on the MMDFC. Memory allocation and sequential code generation follow. The loose eventdriven block-level simulator monitors the execution of timecritical applications, written in DFCL and executed on the MMDFC. It enables debugging at various levels.
018
The DEDOS On-line Scheduler E.I. Luit, V.A.P. Mombarg, pp 119-124
The basic mechanisms of the on-line scheduler for the Dependable Distributed Operating System (DEDOS) am presented. DEDOS supports the reliable execution of tlme-critical applications such as the control of a production system. On each processor in the distributed system, an on-line scheduler (OLS) enforces the timing schedule and also supports exception handling. Tasks are removed from the schedule after an exception and minserted into the schedule after a mconfiguration. It is also possible to execute exceptional schedules or to change to a new schedule. The OLS detects violations of user-defined deadlines, and of network access times.
009
Abstracts
DIMOS: Distributed Monitoring System from Specification to Delivery, the Realization of a Nuclear Power Plant Supervision System using HOOD and ADA P. Jacobs, D. Pluvinage, pp 61-66
To meet the needs of nuclear power plant supervision, a new generation of computer systems, DIMOS, has been developed. A first installation, completed in 1991, now supervises two production units. A major challenge was the choice of a distributed exmfiguration including 15 computers around a double Ethemet LAN, running either VAX/VMS or VAXELN. The postpartitioned design ensures that the code is independent of the distribution. The structured analysis of user requirements was performed using the YOURDON methodology. The design was unplemented using a Hierarchical Object Oriented Design (HOOD) ease tool, from which the large amount of ADA code was generated.
014
This paper presents a mode-change protocol and an approach to fault recovery in hard real-time systems in Ada. The mode change implementation uses standard Ada, although dynamic priority setting is .required. This assures data consistency and deadline meeting, during the mode change protocol. Fault recovery is based on recovery groups of related processes with a common fault-recovery behaviour. When any process fails, the other processes in the group end their execution and a recovery process, m charge of executing the recovery actions, starts. Those features have been successfully implemented and tested as part of a reusable tasking executive intended to develop hard real-time systems in Ada.
015 010
Implementing Mode Changes and Fault Recovery for Hard Real-time Systems in Ada A. Alcmso, J. de la Puente, pp 95-100
Specification of Real Time Systems for Protection Tasks in Automated High-speed Transportation Systems K. Jopke, R. Knigge, E. Sobnieder, pp 67-74
Towards an Environment for Complex Real Time Control Systems Developing A. Garcia, A. Crespo, pp 101-106
The Ward and Mellor system design method is used to describe the functional behaviour of the control and protection system of a high-speed maglev train. A simulation has already been run successfully. A substantial problem is to obtain the proof of the Automatic Train Protection of the whole system on the functional level. The implementation model which contains the functional behaviour is the only object which can he tested against the program code by the experts verifying the system, who need a dearly structured specification to understand the relations between the program code and the model; in particular, the real-time aspect, and guidelines to interpret the system description.
Real-ume and expert systems provide a general framework to solve a great number of problems not completely solved by means of traditional approaches, for example, the control of complex systems. However, in integrating these techniques, some important problems remain. In this paper a new software architecture is proposed. A server task dealing with all the intelligent activities is defined. Critical tasks are extemal to this server and their deadlines are statically guaranteed using the rate monotonic theory. Intelligent activities are organized as internal tasks with multiple versions. An algorithm is presented to select the most-appropriate versions in order to obtain the best quality response.
011
016
A Visual Real.time Programming Language* K. Bastlaens, J.M. Van Campenhout, pp 75-79
Ada Gets Groomed for the Whole Spectrum of Realtime Duties M. Goblin, F J . A . Gielen, pp 107-112
Among the steps taken to tackle the problem of software engineering for real-time applications was the introduction of visual languages. These have the potential to ease programming as they are more expressive than the conventional textual languages. In the domain of real-time applications, the use of visual languages is mainly restricted to software design languages. Automatic code generators are used to generate a code skeleton, which is filled in with fairly "coarse-grained" hand-written textual program fragments. This paper presents a method to extend existing visual design languages to visual programming languages with a much more powerful visual component. 012
One of the specific areas addressed by the AdA-9X revision team deals with requirements posed by real-time applications and introduces a new building block for real-time Ada: the protected record. This provides a low-level data-oriented synchronization mechanism and a primary support for real-time systems. It can be used to program solutions for real-time problems such as mutual exclusion, conditionally shared data, counting semaphores and signals. This paper compares two approaches for the solution of the classical real-time problem of conditional critical regions, using respectively Ada83 tasking and Ada9X protected records. Runtime support and some implementation issues for protected records on muhiprocessor target systems are discussed.
ReaITimeTalk: an Object-Oriented Language for Hard
Real-time Systems E. Brorsson, C. Eriksson, J. Gustafsson, pp 81-86 This paper describes a real-time language which supports both real-time and behavioural modelling, the object-oriented language RealTimeTalk (RTT), based on the well known Smalhalk paradigm. T h e simple syntax of Smalltalk makes it easier to add and restrict features in the language, and provides for the notion of building applications by components. The environment supports design through frameworks, glvang a well-designed and thoroughly tested base for a certain application domain, and also implying a specific design policy. The overall goals of the RTT project are thus to simplify the modelling of real-time systems and in these types of systems to include predictability and determinism. 013
IPRESPS - A Programming Environment for
017
Defining the Semantics of Languages for Programmable Controllers with Synchronous Processes* L. Marc~ P. Le Pare, pp 113-118
Real-tune systems are systems which interact permanently with their environment by receiving external information and producing output commands on it. They are commonly met in factories for the control of industrial processes. In this case, they are often implemented with Programmable Controllers (PCs). The GRAFCET language, which is derived from Petri-Nets, is often used for programming such PCs. Unfortunately, it is not based on a single semantics, which complicates program verification, program exchange and program simulation. We have expressed its semantics with synchronous processes, implemented them with the synchronous language SIGNAL, and investigated methods to make proofs on it.
Partitioning and S.cheduling of Time Critical Tasks M. Ojster~ek, V. Zumer, pp 87-93 An integrated programming environment, IPRESPS, has been developed for static partitioning of time-critical tasks into concurrent modules and for scheduling those modules for the shortest possible execution time on a model of a macro datafiow computer (MMDFC). IPRESPS has modules for program graph generation, partitioning, memory allocation, code generation, and simulation. A time-critical task is transformed into a fine-grained program graph, then into a near-optimal-grained graph. Node size is determined, and nodes are scheduled on the MMDFC. Memory allocation and sequential code generation follow. The loose eventdriven block-level simulator monitors the execution of timecritical applications, written in DFCL and executed on the MMDFC. It enables debugging at various levels.
018
The DEDOS On-line Scheduler E.I. Luit, V.A.P. Mombarg, pp 119-124
The basic mechanisms of the on-line scheduler for the Dependable Distributed Operating System (DEDOS) am presented. DEDOS supports the reliable execution of tlme-critical applications such as the control of a production system. On each processor in the distributed system, an on-line scheduler (OLS) enforces the timing schedule and also supports exception handling. Tasks are removed from the schedule after an exception and minserted into the schedule after a mconfiguration. It is also possible to execute exceptional schedules or to change to a new schedule. The OLS detects violations of user-defined deadlines, and of network access times.