Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470497
M. Adelantado, F. Boniol, S. de Givry
One of the major challenge of next embedded systems is to involve intelligence while preserving the classical real-time properties: (a) reactivity, i.e. the capability to react continuously towards asynchronous inputs, and (b) predictability. Furthermore, one of the main property which is requested in this kind of systems operating in a highly non-deterministic outside environment, is adaptability to new and unexpected conditions, and particularly to dynamic temporal deadlines. Strong predictability often means that it should be possible to prove both the functional and temporal behavior of a system, in response to any combination of signals from outside environment, and particularly to prove that critical tasks meet their deadlines. On the contrary, in non-deterministic environments involving dynamic timing constraints, the assumption that critical tasks meet their deadlines can not be guaranteed. In that sense, strong predictability and adaptability are contradictory requirements. Furthermore, intelligence often means complex computations. In that sense reactivity and punctuality seem also to be incompatible with reasoning capabilities. The aim of this paper is to investigate a programming model, called SATURNE, addressing the issue of intelligent real-time systems, that is how to mix adaptability, reactivity and predictability. We only focuses on adaptability to temporal deadlines, addressing the problem of guaranteeing a response when temporal deadlines may be statically unpredictable. SATURNE is based on a mixed reactive-anytime approach. The main idea is to introduce firstly a reactive model of computation providing predictability, and secondly an anytime model of computation providing adaptability to dynamic temporal deadlines.<>
{"title":"SATURNE: a reactive-anytime programming model for intelligent embedded real-time systems","authors":"M. Adelantado, F. Boniol, S. de Givry","doi":"10.1109/WPDRTS.1995.470497","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470497","url":null,"abstract":"One of the major challenge of next embedded systems is to involve intelligence while preserving the classical real-time properties: (a) reactivity, i.e. the capability to react continuously towards asynchronous inputs, and (b) predictability. Furthermore, one of the main property which is requested in this kind of systems operating in a highly non-deterministic outside environment, is adaptability to new and unexpected conditions, and particularly to dynamic temporal deadlines. Strong predictability often means that it should be possible to prove both the functional and temporal behavior of a system, in response to any combination of signals from outside environment, and particularly to prove that critical tasks meet their deadlines. On the contrary, in non-deterministic environments involving dynamic timing constraints, the assumption that critical tasks meet their deadlines can not be guaranteed. In that sense, strong predictability and adaptability are contradictory requirements. Furthermore, intelligence often means complex computations. In that sense reactivity and punctuality seem also to be incompatible with reasoning capabilities. The aim of this paper is to investigate a programming model, called SATURNE, addressing the issue of intelligent real-time systems, that is how to mix adaptability, reactivity and predictability. We only focuses on adaptability to temporal deadlines, addressing the problem of guaranteeing a response when temporal deadlines may be statically unpredictable. SATURNE is based on a mixed reactive-anytime approach. The main idea is to introduce firstly a reactive model of computation providing predictability, and secondly an anytime model of computation providing adaptability to dynamic temporal deadlines.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123515806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470496
C. Zimmermann, V. Cahill
Traditional object-oriented real-time systems are often limited an that they provide only one approach to real-time object support. Taking the increasing demand for flexible and extensible object support environments into account, we discuss the design and implementation of a small object-oriented real-time executive based on a sub-framework which we call Roo. Roo is a component of the Tigger framework (our proposal for an extensible object support operating system) and is intended to support different object models providing soft real-time behaviour. Roo provides support for different mechanisms and policies for real-time thread management, scheduling and synchronization. In this it serves as a basis for other components of the Tigger framework.<>
{"title":"Roo: a framework for real-time threads","authors":"C. Zimmermann, V. Cahill","doi":"10.1109/WPDRTS.1995.470496","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470496","url":null,"abstract":"Traditional object-oriented real-time systems are often limited an that they provide only one approach to real-time object support. Taking the increasing demand for flexible and extensible object support environments into account, we discuss the design and implementation of a small object-oriented real-time executive based on a sub-framework which we call Roo. Roo is a component of the Tigger framework (our proposal for an extensible object support operating system) and is intended to support different object models providing soft real-time behaviour. Roo provides support for different mechanisms and policies for real-time thread management, scheduling and synchronization. In this it serves as a basis for other components of the Tigger framework.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124537017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470494
J. Caruso
Standard hardware performance and cost concerns are increasingly driving designers of real-time systems toward the use of Commercial Off-The-Shelf (COTS) components. There are many difficulties with this transition yet there is a perceived lack of interest in the subject. It is speculated that the community is not fully aware of the problems being encountered in utilizing COTS components. This paper describes some of the difficulties system designers face, using experiences from on-going efforts to transition a large real-time system, the AEGIS Weapons System (AWS), to a distributed compute plant built with COTS.<>
{"title":"The challenge of the increased use of COTS: a developer's perspective","authors":"J. Caruso","doi":"10.1109/WPDRTS.1995.470494","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470494","url":null,"abstract":"Standard hardware performance and cost concerns are increasingly driving designers of real-time systems toward the use of Commercial Off-The-Shelf (COTS) components. There are many difficulties with this transition yet there is a perceived lack of interest in the subject. It is speculated that the community is not fully aware of the problems being encountered in utilizing COTS components. This paper describes some of the difficulties system designers face, using experiences from on-going efforts to transition a large real-time system, the AEGIS Weapons System (AWS), to a distributed compute plant built with COTS.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124972285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470491
Abhishek Choudhary, V. Gehlot, B. Narahari, M. Benincasa, R. Metzger
Parallel high-performance computing is gaining momentum as a computing platform for many applications. In recent years, the research in software support for parallel computers has mainly addressed scientific and information processing applications. Very little attention has been paid to real-time embedded system requirements on parallel machines. This research investigates some important issues related to designing real-time system software for parallel computers. In this paper, we discuss a formal specification language for real-time systems on parallel architectures. Towards this end we propose the Parallel REal Time SpEcification Language (PRETSEL). We discuss the computation model on which PRETSEL is based, its syntax, its semantics, and its applicability. PRETSEL extends existing algebraic models by providing structured timing constructs, communication primatives and explicit parallelism constructs.<>
{"title":"A specification language for parallel real-time systems","authors":"Abhishek Choudhary, V. Gehlot, B. Narahari, M. Benincasa, R. Metzger","doi":"10.1109/WPDRTS.1995.470491","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470491","url":null,"abstract":"Parallel high-performance computing is gaining momentum as a computing platform for many applications. In recent years, the research in software support for parallel computers has mainly addressed scientific and information processing applications. Very little attention has been paid to real-time embedded system requirements on parallel machines. This research investigates some important issues related to designing real-time system software for parallel computers. In this paper, we discuss a formal specification language for real-time systems on parallel architectures. Towards this end we propose the Parallel REal Time SpEcification Language (PRETSEL). We discuss the computation model on which PRETSEL is based, its syntax, its semantics, and its applicability. PRETSEL extends existing algebraic models by providing structured timing constructs, communication primatives and explicit parallelism constructs.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130936942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470517
M. Boasson
Reactive systems, i.e. systems reacting to events in their environment, base their operation on models of the objects of interest in the environment. In the current practice these models are implemented as algorithms ultimately relating observations to actions. This approach results in systems that are rather inflexible and sometimes difficult to maintain. In addition, the different uses made of the various models easily results in built-in inconsistencies, leading to undesirable systems behaviour. An alternative approach is sketched in this short paper in which models are represented explicitly in the system.<>
{"title":"Model-based system development","authors":"M. Boasson","doi":"10.1109/WPDRTS.1995.470517","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470517","url":null,"abstract":"Reactive systems, i.e. systems reacting to events in their environment, base their operation on models of the objects of interest in the environment. In the current practice these models are implemented as algorithms ultimately relating observations to actions. This approach results in systems that are rather inflexible and sometimes difficult to maintain. In addition, the different uses made of the various models easily results in built-in inconsistencies, leading to undesirable systems behaviour. An alternative approach is sketched in this short paper in which models are represented explicitly in the system.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116409004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470485
A. Saha, R. Neogi
A candidate network function is accurately defined for real-time parallel computers. A concise, time-driven, flit-based, priority-driven, wormhole-routed, network simulator has been designed. Experimentation is performed by monitoring the latency and the throughput with variations in different network parameters. Initially the destination address, message length and message priority are generated randomly with a uniform distribution. Then, various non-uniformities are introduced to mimic realistic applications. Results are plotted and analyzed.<>
{"title":"A study of network routers for real-time parallel computers","authors":"A. Saha, R. Neogi","doi":"10.1109/WPDRTS.1995.470485","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470485","url":null,"abstract":"A candidate network function is accurately defined for real-time parallel computers. A concise, time-driven, flit-based, priority-driven, wormhole-routed, network simulator has been designed. Experimentation is performed by monitoring the latency and the throughput with variations in different network parameters. Initially the destination address, message length and message priority are generated randomly with a uniform distribution. Then, various non-uniformities are introduced to mimic realistic applications. Results are plotted and analyzed.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131093768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470489
Y. Okawa, T. Yoneda
Most verification algorithms for schedulability of real-time systems are based on an approximate computation which only considers worst cases. Although they always find correct schedulings, in which any task never violates its deadline, those schedulings are sometimes too strict. In this paper, in order to verify schedulability more precisely we propose a verification method based on the state space traversal of the time Petri net that models the given real-time system and the given scheduling. We also extend time Petri nets in order to model round-robin scheduling easily. Some experimental results obtained by the proposed method are shown.<>
{"title":"Verification of schedulability of real-time systems with extended time Petri nets","authors":"Y. Okawa, T. Yoneda","doi":"10.1109/WPDRTS.1995.470489","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470489","url":null,"abstract":"Most verification algorithms for schedulability of real-time systems are based on an approximate computation which only considers worst cases. Although they always find correct schedulings, in which any task never violates its deadline, those schedulings are sometimes too strict. In this paper, in order to verify schedulability more precisely we propose a verification method based on the state space traversal of the time Petri net that models the given real-time system and the given scheduling. We also extend time Petri nets in order to model round-robin scheduling easily. Some experimental results obtained by the proposed method are shown.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"218 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125364981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470487
G. Greenwood, C. Lang, S. Hurley
Finding feasible schedules for tasks running in hard, real-time distributed computing systems is generally NP-hard. This paper describes a heuristic algorithm using evolutionary strategies. Our results indicate that the evolutionary strategies can find feasible schedules (assuming they exist) in very short periods of time.<>
{"title":"Scheduling tasks in real-time systems using evolutionary strategies","authors":"G. Greenwood, C. Lang, S. Hurley","doi":"10.1109/WPDRTS.1995.470487","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470487","url":null,"abstract":"Finding feasible schedules for tasks running in hard, real-time distributed computing systems is generally NP-hard. This paper describes a heuristic algorithm using evolutionary strategies. Our results indicate that the evolutionary strategies can find feasible schedules (assuming they exist) in very short periods of time.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"166 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126173500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470501
Tatsuhiro Tsuchiya, Yoshiaki Kakuda, T. Kikuno
In a distributed real-time system, tolerance to faults on processing nodes in the system is achieved by means of redundant nodes and a fault-tolerant scheduling algorithm. Since redundant nodes increase total failure rate of the system, the number of such redundant nodes should be small. This paper proposes a procedure for fault-tolerant scheduling, which realizes fault-tolerance via a small number of redundant nodes. The procedure is based on such a technique that allows multiple copies of a task to be executed concurrently. It achieves efficient utilization of nodes by forcing copies being executed to terminate immediately after having obtained the first result of these copies. A fundamental scheduling algorithm, into which the procedure is incorporated, is defined and its simulation results are shown.<>
{"title":"Fault-tolerant scheduling algorithm for distributed real-time systems","authors":"Tatsuhiro Tsuchiya, Yoshiaki Kakuda, T. Kikuno","doi":"10.1109/WPDRTS.1995.470501","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470501","url":null,"abstract":"In a distributed real-time system, tolerance to faults on processing nodes in the system is achieved by means of redundant nodes and a fault-tolerant scheduling algorithm. Since redundant nodes increase total failure rate of the system, the number of such redundant nodes should be small. This paper proposes a procedure for fault-tolerant scheduling, which realizes fault-tolerance via a small number of redundant nodes. The procedure is based on such a technique that allows multiple copies of a task to be executed concurrently. It achieves efficient utilization of nodes by forcing copies being executed to terminate immediately after having obtained the first result of these copies. A fundamental scheduling algorithm, into which the procedure is incorporated, is defined and its simulation results are shown.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"41 21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126070803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470493
W. Jonker, L. Nieuwenhuis
We discuss requirements and techniques for the service data point (SDP) in intelligent network (IN) architectures in telecommunications systems. The SDP must provide real-time, simultaneous access to high volume databases. We give a short overview of SDP requirements derived from currently developed and future IN telecommunications services.<>
{"title":"Overview of databases requirements for intelligent networks","authors":"W. Jonker, L. Nieuwenhuis","doi":"10.1109/WPDRTS.1995.470493","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470493","url":null,"abstract":"We discuss requirements and techniques for the service data point (SDP) in intelligent network (IN) architectures in telecommunications systems. The SDP must provide real-time, simultaneous access to high volume databases. We give a short overview of SDP requirements derived from currently developed and future IN telecommunications services.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129273614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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