Pub Date : 1998-04-20DOI: 10.1109/ISORC.1998.666790
B. Nielsen, Shangping Ren, G. Agha
We present a coordination language and its semantics for specification and implementation of object-oriented real-time systems. Real-time systems operate under real-time constraints, and our language supports expression thereof. In our language, a system is modeled by two separate but complementary descriptions: A collection of objects define the system's structure and functional behavior and a set of interaction constraints define how these objects may interact. Our language thereby supports development of real-time systems by enabling objects build in isolation or re-used from other systems to be composed via interaction constraints. We use the Actor model to describe objects and the concept of real-time synchronizers to describe interaction constraints. Our model is accompanied by a formal semantics that precisely defines what real-time constraints means, and what constitutes a program's correct real-time behaviors. The semantics defines how the system may evolve in the real-time domain, and what progress guarantees the language makes. We briefly discuss implementation problems and potential solutions.
{"title":"Specification of real-time interaction constraints","authors":"B. Nielsen, Shangping Ren, G. Agha","doi":"10.1109/ISORC.1998.666790","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666790","url":null,"abstract":"We present a coordination language and its semantics for specification and implementation of object-oriented real-time systems. Real-time systems operate under real-time constraints, and our language supports expression thereof. In our language, a system is modeled by two separate but complementary descriptions: A collection of objects define the system's structure and functional behavior and a set of interaction constraints define how these objects may interact. Our language thereby supports development of real-time systems by enabling objects build in isolation or re-used from other systems to be composed via interaction constraints. We use the Actor model to describe objects and the concept of real-time synchronizers to describe interaction constraints. Our model is accompanied by a formal semantics that precisely defines what real-time constraints means, and what constitutes a program's correct real-time behaviors. The semantics defines how the system may evolve in the real-time domain, and what progress guarantees the language makes. We briefly discuss implementation problems and potential solutions.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130642767","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666770
A. Polze, M. Malek
The Common Object Request Broker Architecture (CORBA) is a widely-accepted, standardized system integration framework based on distributed object technologies. CORBA is focused on facilitating general computing environments and does not explicitly address the needs of responsive (fault-tolerant, real-time) computing. Therefore, the question remains how to extend today's CORBA implementations for support of responsive computing. In this paper we propose a CORBA-based distributed framework for responsive execution of CORBA method invocations. The framework exploits consensus for synchronization, reliable communication, and fault diagnosis among replicated server objects. Within the replicated server objects, we use the "Composite Objects" technique for predictable integration of CORBA and responsive computing. We present a methodology for creating objects which interface to CORBA while simultaneously supporting fault-tolerance and real-time requirements.
{"title":"Responsive computing with CORBA","authors":"A. Polze, M. Malek","doi":"10.1109/ISORC.1998.666770","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666770","url":null,"abstract":"The Common Object Request Broker Architecture (CORBA) is a widely-accepted, standardized system integration framework based on distributed object technologies. CORBA is focused on facilitating general computing environments and does not explicitly address the needs of responsive (fault-tolerant, real-time) computing. Therefore, the question remains how to extend today's CORBA implementations for support of responsive computing. In this paper we propose a CORBA-based distributed framework for responsive execution of CORBA method invocations. The framework exploits consensus for synchronization, reliable communication, and fault diagnosis among replicated server objects. Within the replicated server objects, we use the \"Composite Objects\" technique for predictable integration of CORBA and responsive computing. We present a methodology for creating objects which interface to CORBA while simultaneously supporting fault-tolerance and real-time requirements.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134368509","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666777
T. Ishida, M. Takizawa
An approach to making distributed systems fault-tolerant is to replicate objects. The replicas have to be realized in different types of computers. In the active replication, the replicas are computed and communicated in the same synchronous way. The computation speed of the process depends on the slowest replica. We discuss a pseudo-active replication where events may not occur simultaneously, not in the same order, and may not occur in the replicas.
{"title":"Pseudo-active replication of objects in heterogeneous clusters","authors":"T. Ishida, M. Takizawa","doi":"10.1109/ISORC.1998.666777","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666777","url":null,"abstract":"An approach to making distributed systems fault-tolerant is to replicate objects. The replicas have to be realized in different types of computers. In the active replication, the replicas are computed and communicated in the same synchronous way. The computation speed of the process depends on the slowest replica. We discuss a pseudo-active replication where events may not occur simultaneously, not in the same order, and may not occur in the replicas.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"207 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133715614","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666771
K. Kim, C. Subbaraman
One of the major components required for the construction of future complex real-time computer systems (RTCS) needed in safety-critical applications is a timeliness-guaranteed operating system. A model of an operating system kernel called the DREAM kernel that can support both conventional real-time processes and new-style real-time objects has been formulated. The key emphasis in formulating the DREAM kernel was in the realization of guaranteed timely responses to the service requests from supported client programs. This paper presents a summary of the main structuring principles that were exploited to realize guaranteed timely service capabilities while maintaining the modular and easily expandable structure in the DREAM kernel. Implementation of real-time processes and real-time objects involves designing various calls to DREAM kernel services. A library of functions, called the DREAM library and providing user-friendly interfaces to the DREAM kernel, has been developed in the authors' laboratory. This library consists of a collection of specific C++ classes. A 32-bit prototype version of the DREAM kernel, version D3.0, encapsulated by the DREAM library that supports well-structured real-time application programming in C++ has been implemented. This prototype version has been used in efficient development of several real-time object structured applications including a non-trivial defense C/sup 3/ system, a steel factory control system, and an advanced traffic management system.
{"title":"Principles of constructing a timeliness-guaranteed kernel and time-triggered message-triggered object support mechanisms","authors":"K. Kim, C. Subbaraman","doi":"10.1109/ISORC.1998.666771","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666771","url":null,"abstract":"One of the major components required for the construction of future complex real-time computer systems (RTCS) needed in safety-critical applications is a timeliness-guaranteed operating system. A model of an operating system kernel called the DREAM kernel that can support both conventional real-time processes and new-style real-time objects has been formulated. The key emphasis in formulating the DREAM kernel was in the realization of guaranteed timely responses to the service requests from supported client programs. This paper presents a summary of the main structuring principles that were exploited to realize guaranteed timely service capabilities while maintaining the modular and easily expandable structure in the DREAM kernel. Implementation of real-time processes and real-time objects involves designing various calls to DREAM kernel services. A library of functions, called the DREAM library and providing user-friendly interfaces to the DREAM kernel, has been developed in the authors' laboratory. This library consists of a collection of specific C++ classes. A 32-bit prototype version of the DREAM kernel, version D3.0, encapsulated by the DREAM library that supports well-structured real-time application programming in C++ has been implemented. This prototype version has been used in efficient development of several real-time object structured applications including a non-trivial defense C/sup 3/ system, a steel factory control system, and an advanced traffic management system.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130040422","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666805
P. Herrmann, G. Graw, H. Krumm
Many modern chemical plants have to be modelled as complex hybrid systems consisting of various continuous and event-discrete components. Besides the modular and easy to read specification, the formal verification of required properties (e.g., safety properties) is a major problem, due to the complexity of the models. In practice, mostly informal argumentations exist which show that certain properties hold. The informal argumentation for one specific property does not deal with the complex system model as a whole but considers specific parts and aspects only. Our approach supports formal proofs which correspond to the informal argumentations even with respect to the use of subsystems only. It is based on the specification language cTLA supporting modular descriptions of hybrid systems. We outline cTLA and introduce the approach by means of a hybrid example system.
{"title":"Compositional specification and structured verification of hybrid systems in cTLA","authors":"P. Herrmann, G. Graw, H. Krumm","doi":"10.1109/ISORC.1998.666805","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666805","url":null,"abstract":"Many modern chemical plants have to be modelled as complex hybrid systems consisting of various continuous and event-discrete components. Besides the modular and easy to read specification, the formal verification of required properties (e.g., safety properties) is a major problem, due to the complexity of the models. In practice, mostly informal argumentations exist which show that certain properties hold. The informal argumentation for one specific property does not deal with the complex system model as a whole but considers specific parts and aspects only. Our approach supports formal proofs which correspond to the informal argumentations even with respect to the use of subsystems only. It is based on the specification language cTLA supporting modular descriptions of hybrid systems. We outline cTLA and introduce the approach by means of a hybrid example system.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"196 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114749065","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666796
Jung-Guk Kim, Moon-hae Kim, B. Min, D. B. Im
The TMO (Time-triggered Message-triggered Object) model is a real time object model pursuing the timeliness guaranteed computing paradigm. A TMO contains two types of methods: time triggered method activated by its internal clock and message triggered method activated by a request from a client. We present the functions and the design techniques of a middleware platform to support execution of TMOs on the Windows environment, named WTMOS (Windows TMO System). The WTMOS platform does not support the concept of design time guarantee. But, as middleware platform, it supports soft real time system by trying to meet the goal of on-time activation and finishing within deadlines imposed on time triggered and message triggered methods in TMOs. It also offers used defined deadline exception handlers to compensate for the lack of timeliness guaranteed design. Besides the above functions, the activation sources of message triggered methods on WTMOS are expanded so that it can be activated not only by distributed IPC messages but also by Windows system messages. As a result, message triggered methods now can play the roll of Windows message callback functions naturally. This is to add window management facilities and interfaces of Win32 API to the TMO model. Therefore, the TMO model and WTMOS together can be regarded as a powerful development environment for typical soft real time applications such as multimedia services and virtual reality services.
{"title":"A soft real-time TMO platform-WTMOS-and implementation techniques","authors":"Jung-Guk Kim, Moon-hae Kim, B. Min, D. B. Im","doi":"10.1109/ISORC.1998.666796","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666796","url":null,"abstract":"The TMO (Time-triggered Message-triggered Object) model is a real time object model pursuing the timeliness guaranteed computing paradigm. A TMO contains two types of methods: time triggered method activated by its internal clock and message triggered method activated by a request from a client. We present the functions and the design techniques of a middleware platform to support execution of TMOs on the Windows environment, named WTMOS (Windows TMO System). The WTMOS platform does not support the concept of design time guarantee. But, as middleware platform, it supports soft real time system by trying to meet the goal of on-time activation and finishing within deadlines imposed on time triggered and message triggered methods in TMOs. It also offers used defined deadline exception handlers to compensate for the lack of timeliness guaranteed design. Besides the above functions, the activation sources of message triggered methods on WTMOS are expanded so that it can be activated not only by distributed IPC messages but also by Windows system messages. As a result, message triggered methods now can play the roll of Windows message callback functions naturally. This is to add window management facilities and interfaces of Win32 API to the TMO model. Therefore, the TMO model and WTMOS together can be regarded as a powerful development environment for typical soft real time applications such as multimedia services and virtual reality services.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124983468","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666801
J. Kaiser, M. Livani
The paper focuses on method invocation of real-time objects in a CAN-based distributed real-time system. A simple object model is introduced, which allows the convenient modelling of hardware and software components. Related to the object model, two issues are discussed. Firstly, a model is introduced which allows to form and address object groups. This reflects a basic need in a real-time system to distribute information to multiple clients efficiently. Secondly, the paper discusses an approach to express timing requirements for object invocations. To achieve distributed consensus on communication resource access, an EDF-like approach is introduced, which takes advantage of knowledge about deadlines, the number of remaining communication activities and the remaining worst-case execution time for the invoked method at each point of time.
{"title":"Invocation of real-time objects in a CAN bus-system","authors":"J. Kaiser, M. Livani","doi":"10.1109/ISORC.1998.666801","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666801","url":null,"abstract":"The paper focuses on method invocation of real-time objects in a CAN-based distributed real-time system. A simple object model is introduced, which allows the convenient modelling of hardware and software components. Related to the object model, two issues are discussed. Firstly, a model is introduced which allows to form and address object groups. This reflects a basic need in a real-time system to distribute information to multiple clients efficiently. Secondly, the paper discusses an approach to express timing requirements for object invocations. To achieve distributed consensus on communication resource access, an EDF-like approach is introduced, which takes advantage of knowledge about deadlines, the number of remaining communication activities and the remaining worst-case execution time for the invoked method at each point of time.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129314704","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666802
Shahab Baqai, R. Paul, H. Fahmi, A. Bashandy, A. Ghafoor
We propose a dynamic bandwidth management scheme for asynchronous LANs that uses the concept of time division multiple access (TDMA). The scheme is to ensure quality of service (QoS) for multimedia applications. Significant performance improvement is observed through experimental results. In particular, the transmission rates for multimedia hosts improve significantly with low jitter variations in media streams. We also propose a framework for graceful degradation of play-out quality of multimedia objects in case the LAN's total capacity is not sufficient to meet the overall demand.
{"title":"Real time resource allocation for multimedia object communication","authors":"Shahab Baqai, R. Paul, H. Fahmi, A. Bashandy, A. Ghafoor","doi":"10.1109/ISORC.1998.666802","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666802","url":null,"abstract":"We propose a dynamic bandwidth management scheme for asynchronous LANs that uses the concept of time division multiple access (TDMA). The scheme is to ensure quality of service (QoS) for multimedia applications. Significant performance improvement is observed through experimental results. In particular, the transmission rates for multimedia hosts improve significantly with low jitter variations in media streams. We also propose a framework for graceful degradation of play-out quality of multimedia objects in case the LAN's total capacity is not sufficient to meet the overall demand.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126009447","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 : 1998-04-20DOI: 10.1109/ISORC.1998.666807
T. Kanezuka, M. Takizawa
The paper discusses how to make a distributed object system flexible so as to satisfy the application's requirement in the change of the system environment. Each object supports other objects with quality of service (QoS). The change of the system is modeled to be the change of not only types of service but also QoS supported by the objects. We discuss equivalency and compatibility relations among operations with respect to QoS. By using the QoS based relations, we discuss a QoS based compensating way to recover the object from the less qualified state. Finally, we discuss QoS based replication of objects to make required QoS available even if some replicas get less qualified; here, the replicas may not necessarily be the same.
{"title":"Quality-based flexibility in distributed objects","authors":"T. Kanezuka, M. Takizawa","doi":"10.1109/ISORC.1998.666807","DOIUrl":"https://doi.org/10.1109/ISORC.1998.666807","url":null,"abstract":"The paper discusses how to make a distributed object system flexible so as to satisfy the application's requirement in the change of the system environment. Each object supports other objects with quality of service (QoS). The change of the system is modeled to be the change of not only types of service but also QoS supported by the objects. We discuss equivalency and compatibility relations among operations with respect to QoS. By using the QoS based relations, we discuss a QoS based compensating way to recover the object from the less qualified state. Finally, we discuss QoS based replication of objects to make required QoS available even if some replicas get less qualified; here, the replicas may not necessarily be the same.","PeriodicalId":186028,"journal":{"name":"Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116786151","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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