Pub Date : 1994-04-28DOI: 10.1109/WPDRTS.1994.365645
B. Furht
The fundamental characteristics of multimedia systems is that they incorporate continuous media, such as voice, video, and animated graphics. This implies the need for multimedia systems to handle data with strict timing requirements and at high rate. This article discusses important real-time issues in distributed multimedia systems including media synchronization, operating system support for continuous media, scheduling issues for on-demand multimedia applications, and real-time architectures of future interactive TV-converter boxes. Several solutions of these problems are presented in the article.<>
{"title":"Real-time issues in distributed multimedia systems","authors":"B. Furht","doi":"10.1109/WPDRTS.1994.365645","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365645","url":null,"abstract":"The fundamental characteristics of multimedia systems is that they incorporate continuous media, such as voice, video, and animated graphics. This implies the need for multimedia systems to handle data with strict timing requirements and at high rate. This article discusses important real-time issues in distributed multimedia systems including media synchronization, operating system support for continuous media, scheduling issues for on-demand multimedia applications, and real-time architectures of future interactive TV-converter boxes. Several solutions of these problems are presented in the article.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116949745","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365637
B. Abou-Haider, E. Fernández, T. B. Horton
We describe here a systematic method for the design and modeling of flexible manufacturing systems, using object-oriented concepts and Petri nets. We first define the system components in terms of an object model consisting of hierarchical sets of classes and associations. Then, we model the dynamic aspects of the system using statecharts, including exceptions and abnormal behavior. As a third step, we derive Petri nets from those statecharts to realize the concurrency present in the system. Finally we develop a hierarchy of controllers, corresponding to the layers of the object model, for the independent components of the system based on the Petri nets obtained in the previous step. The approach is systematic and relatively easy to apply. It is illustrated through a realistic example.<>
{"title":"An object-oriented methodology for the design of control software for flexible manufacturing systems","authors":"B. Abou-Haider, E. Fernández, T. B. Horton","doi":"10.1109/WPDRTS.1994.365637","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365637","url":null,"abstract":"We describe here a systematic method for the design and modeling of flexible manufacturing systems, using object-oriented concepts and Petri nets. We first define the system components in terms of an object model consisting of hierarchical sets of classes and associations. Then, we model the dynamic aspects of the system using statecharts, including exceptions and abnormal behavior. As a third step, we derive Petri nets from those statecharts to realize the concurrency present in the system. Finally we develop a hierarchy of controllers, corresponding to the layers of the object model, for the independent components of the system based on the Petri nets obtained in the previous step. The approach is systematic and relatively easy to apply. It is illustrated through a realistic example.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129414121","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365636
R. Steigerwald, C. Warack, D. Cook
A rapid prototyping tool for distributed real-time systems relies on a repository of reusable software components (or objects) to support application development. The goal is to quickly generate systems that meet hard real-time constraints. The components in the repository must be retrievable, easily reusable, and possess attributes that facilitate scheduling analysis. Components written in Ada 9X with appropriate attributes and structure enhance the methodology.<>
{"title":"Issues in integrating reusable Ada 9X objects into distributed real-time systems","authors":"R. Steigerwald, C. Warack, D. Cook","doi":"10.1109/WPDRTS.1994.365636","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365636","url":null,"abstract":"A rapid prototyping tool for distributed real-time systems relies on a repository of reusable software components (or objects) to support application development. The goal is to quickly generate systems that meet hard real-time constraints. The components in the repository must be retrievable, easily reusable, and possess attributes that facilitate scheduling analysis. Components written in Ada 9X with appropriate attributes and structure enhance the methodology.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114492546","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365639
M. Adelantado, F. Boniol, M. Cubero-Castan, B. Lécussan
In this paper, we first propose a mixed synchronous/asynchronous programming model for distributed reactive systems. This model is built around a set of synchronous reactive kernels, written in Esterel synchronous language, each of them controlling a set of asynchronous and time-consuming tasks, through a set of tasks control directives. In this paper, we focus on protocols allowing the implementation of a set of synchronous reactive kernels on a distributed machine. These protocols are based on a model of computation named the "weak synchronous hypothesis", assuming that reaction times and communication times of the synchronous network can be upper bounded at compile-time. In order to validate this programming model, we have developed a compiler allowing the expression of a real-time application as a set of distributed reactive kernels, written in Esterel synchronous language. The compiler automatically produces a simulator of the real-time application, written in C language and running on a Unix workstation. Finally, we describe preliminary results we have obtained on actual applications, taken from associate avionics systems.<>
{"title":"Synchronous/anytime programming for distributed reactive systems","authors":"M. Adelantado, F. Boniol, M. Cubero-Castan, B. Lécussan","doi":"10.1109/WPDRTS.1994.365639","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365639","url":null,"abstract":"In this paper, we first propose a mixed synchronous/asynchronous programming model for distributed reactive systems. This model is built around a set of synchronous reactive kernels, written in Esterel synchronous language, each of them controlling a set of asynchronous and time-consuming tasks, through a set of tasks control directives. In this paper, we focus on protocols allowing the implementation of a set of synchronous reactive kernels on a distributed machine. These protocols are based on a model of computation named the \"weak synchronous hypothesis\", assuming that reaction times and communication times of the synchronous network can be upper bounded at compile-time. In order to validate this programming model, we have developed a compiler allowing the expression of a real-time application as a set of distributed reactive kernels, written in Esterel synchronous language. The compiler automatically produces a simulator of the real-time application, written in C language and running on a Unix workstation. Finally, we describe preliminary results we have obtained on actual applications, taken from associate avionics systems.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117168725","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365642
C. Kelling, G. Hommel
The applicability of well known medium access control (MAC) protocols for real time systems is of great interest for the development of suitable communication schemes in this field. This paper introduces models for the priority schemes of well known token protocols, since they provide deterministic behaviour and therefore guarantee time constraints. Deterministic and Stochastic Petri Nets (DSPN) are used as a flexible graphical description technique for concurrent and distributed systems. Powerful analysis tools for this class of timed Petri nets are also available. Performance evaluations of the presented models allow to determine the transmission characteristic of the protocols considering the different priority levels.<>
{"title":"Modeling priority schemes with timed Petri nets","authors":"C. Kelling, G. Hommel","doi":"10.1109/WPDRTS.1994.365642","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365642","url":null,"abstract":"The applicability of well known medium access control (MAC) protocols for real time systems is of great interest for the development of suitable communication schemes in this field. This paper introduces models for the priority schemes of well known token protocols, since they provide deterministic behaviour and therefore guarantee time constraints. Deterministic and Stochastic Petri Nets (DSPN) are used as a flexible graphical description technique for concurrent and distributed systems. Powerful analysis tools for this class of timed Petri nets are also available. Performance evaluations of the presented models allow to determine the transmission characteristic of the protocols considering the different priority levels.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131063659","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365634
J. Caruso
A substantial amount of time and money has been invested in large complex reactive systems. The size of these legacy systems often puts an organization into the position of having too much invested to completely redesign and reimplement the product. Therefore, methods for transitioning these systems to more modern architectures must be synthesized, after the fact, from the existing programming artifacts. Due to the mainframe technology upon which they were based, many of these systems are monolithic and require repartitioning. There is some solace in the fact that many systems have existing software partitionings based on many independent threads of control which become candidates for distributed subsystems. The challenge lies in picking aggregates of these threads which present a reasonable computational load and have loose enough coupling to permit distribution of the final system.<>
{"title":"Partitioning complex real-time systems for distribution","authors":"J. Caruso","doi":"10.1109/WPDRTS.1994.365634","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365634","url":null,"abstract":"A substantial amount of time and money has been invested in large complex reactive systems. The size of these legacy systems often puts an organization into the position of having too much invested to completely redesign and reimplement the product. Therefore, methods for transitioning these systems to more modern architectures must be synthesized, after the fact, from the existing programming artifacts. Due to the mainframe technology upon which they were based, many of these systems are monolithic and require repartitioning. There is some solace in the fact that many systems have existing software partitionings based on many independent threads of control which become candidates for distributed subsystems. The challenge lies in picking aggregates of these threads which present a reasonable computational load and have loose enough coupling to permit distribution of the final system.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132843866","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365651
Too-Seng Tia, J.W.-S. Liu
In this paper, we propose an efficient algorithm to statically assign tasks and logical resources to the processors, taking into account the blocking times due to resource contention. We formulate the assignment problem using an assignment graph where the weights on the edges of the graph represent the desirability of assigning the tasks (connected by the edges) to the processors. These weights are computed based on the resource usages, communication costs, and the priorities of the tasks. An efficient clustering and graph-bisection algorithm is used to find an assignment of the tasks and resources such that the total communication costs and total blocking time are minimized, subject to the constraint that the tasks are schedulable after the assignment. Experimental results indicate the effectiveness of our algorithm.<>
{"title":"Task and resource assignment in distributed real-time systems","authors":"Too-Seng Tia, J.W.-S. Liu","doi":"10.1109/WPDRTS.1994.365651","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365651","url":null,"abstract":"In this paper, we propose an efficient algorithm to statically assign tasks and logical resources to the processors, taking into account the blocking times due to resource contention. We formulate the assignment problem using an assignment graph where the weights on the edges of the graph represent the desirability of assigning the tasks (connected by the edges) to the processors. These weights are computed based on the resource usages, communication costs, and the priorities of the tasks. An efficient clustering and graph-bisection algorithm is used to find an assignment of the tasks and resources such that the total communication costs and total blocking time are minimized, subject to the constraint that the tasks are schedulable after the assignment. Experimental results indicate the effectiveness of our algorithm.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122519948","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365638
G. Li, J. Bacon
This paper describes a distributed environment for real-time applications. The context of this research is Open Distributed Processing (ODP). It is the stringent timeliness and performance requirements of real-time applications that are the primary source of problems posed by real-time applications. The services provided by existing distributed system environments predate the present concerns of real-time applications and provide insufficient and inappropriate services for supporting them. For example, current standards for distributed processing, such as the OSF DCE, OMG CORBA and ISO RM-ODP make no mention of real-time issues. This paper shows how it is possible to extend a distributed system environment to support real-time applications and hence help avoid these problems. The principal issues covered by this paper are: real-time system environment characteristics, i.e. the problems to be addressed; distributed real-time object execution; and a distributed real-time programming model.<>
{"title":"Supporting distributed real-time objects","authors":"G. Li, J. Bacon","doi":"10.1109/WPDRTS.1994.365638","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365638","url":null,"abstract":"This paper describes a distributed environment for real-time applications. The context of this research is Open Distributed Processing (ODP). It is the stringent timeliness and performance requirements of real-time applications that are the primary source of problems posed by real-time applications. The services provided by existing distributed system environments predate the present concerns of real-time applications and provide insufficient and inappropriate services for supporting them. For example, current standards for distributed processing, such as the OSF DCE, OMG CORBA and ISO RM-ODP make no mention of real-time issues. This paper shows how it is possible to extend a distributed system environment to support real-time applications and hence help avoid these problems. The principal issues covered by this paper are: real-time system environment characteristics, i.e. the problems to be addressed; distributed real-time object execution; and a distributed real-time programming model.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"165 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133349512","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365646
P. V. D. van der Stok, P. Thijssen
Distributed nested objects are considered as the building blocks for distributed real-time systems. Objects are stored in memory. Objects can be related in two ways: (1) syntactically: they have a common object from which they are invoked and (2) time-wise: the actions on the objects always occur at the same moments. The consistency of a set of related objects is assured with concurrency control algorithms originating from database systems. Three types of algorithms are considered: optimistic concurrency control, time stamp ordering and two phase locking. The performance of these three algorithms are compared.<>
{"title":"Simulation of distributed real-time transactions","authors":"P. V. D. van der Stok, P. Thijssen","doi":"10.1109/WPDRTS.1994.365646","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365646","url":null,"abstract":"Distributed nested objects are considered as the building blocks for distributed real-time systems. Objects are stored in memory. Objects can be related in two ways: (1) syntactically: they have a common object from which they are invoked and (2) time-wise: the actions on the objects always occur at the same moments. The consistency of a set of related objects is assured with concurrency control algorithms originating from database systems. Three types of algorithms are considered: optimistic concurrency control, time stamp ordering and two phase locking. The performance of these three algorithms are compared.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129908764","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 : 1994-04-28DOI: 10.1109/WPDRTS.1994.365656
E. Luit, J. Martin
A distributed fault-tolerant Convergence Function (CF) is proposed to resynchronize clocks with high precision. The CF can be used in conjunction with drift corrections which significantly increases the period between resynchronizations. This is important when clock drifts are large, because clock synchronization overhead then becomes intolerable. Clock differences are disseminated by a reliable message protocol after the clock valves are exchanged. All correct clocks then have identical copies of a matrix of clock differences. Matrix elements of correct clocks satisfy several relations. A subset of clocks that satisfy these relations defines an average clock. The influence of incorrect clocks on the average clock is shown to be bounded. The resynchronization is precise if clock reading errors are small, including uncertainties in transmission delays. Incorrect clocks may run too slow or too fast, exhibit omission failures or report inconsistent values.<>
{"title":"A convergence function for clock synchronization protocols","authors":"E. Luit, J. Martin","doi":"10.1109/WPDRTS.1994.365656","DOIUrl":"https://doi.org/10.1109/WPDRTS.1994.365656","url":null,"abstract":"A distributed fault-tolerant Convergence Function (CF) is proposed to resynchronize clocks with high precision. The CF can be used in conjunction with drift corrections which significantly increases the period between resynchronizations. This is important when clock drifts are large, because clock synchronization overhead then becomes intolerable. Clock differences are disseminated by a reliable message protocol after the clock valves are exchanged. All correct clocks then have identical copies of a matrix of clock differences. Matrix elements of correct clocks satisfy several relations. A subset of clocks that satisfy these relations defines an average clock. The influence of incorrect clocks on the average clock is shown to be bounded. The resynchronization is precise if clock reading errors are small, including uncertainties in transmission delays. Incorrect clocks may run too slow or too fast, exhibit omission failures or report inconsistent values.<<ETX>>","PeriodicalId":275053,"journal":{"name":"Second Workshop on Parallel and Distributed Real-Time Systems","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128742367","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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