J. Stein, T. Andrews, B. Kent, Katie Rotzell, D. Weinreb
While the availability of commercial systems from several vendors indicates maturity in object database management technology, there are numerous issues which remain. This panel will attempt to expose and discuss several of these issues. Part of the performance advantage realized by object database management systems comes from linking application programs with the database management system, and the use of large virtual memory caches. This is acceptable in engineering applications where previously large amounts of data were read from the file system into an application program's data space. However, the potential impact on database integrity of giving application programs direct access to very large database management system caches will be of great concern in commercial applications. How can these concerns be addressed with minimal impact on the performance advantage of object database management? There appear to be two distinct approaches to object query languages: extensions to SQL and programming language extensions. SQL extensions might provide a fast path to a standard, but would have the traditional impedance mismatch problems associated with embedded query languages. Language extensions are elegant in that they use the same syntax as the programming language and do not suffer from impedance mismatch problems. However, language extensions would probably make standards more difficult to arrive at as it would require the coordination of extensions to multiple languages. Which of the approaches is most appropriate? In which order should these two approaches be addressed by the object database vendors and standards bodies? One might argue that a good deal of research in relational theory has had little or no impact on commercial relational systems (e.g., relational dependence theory). From a vendor's perspective, what are the hard, interesting research issues whose resolution would allow you to build better systems?
{"title":"Issues in object database management","authors":"J. Stein, T. Andrews, B. Kent, Katie Rotzell, D. Weinreb","doi":"10.1145/97945.97973","DOIUrl":"https://doi.org/10.1145/97945.97973","url":null,"abstract":"While the availability of commercial systems from several vendors indicates maturity in object database management technology, there are numerous issues which remain. This panel will attempt to expose and discuss several of these issues.\u0000Part of the performance advantage realized by object database management systems comes from linking application programs with the database management system, and the use of large virtual memory caches. This is acceptable in engineering applications where previously large amounts of data were read from the file system into an application program's data space. However, the potential impact on database integrity of giving application programs direct access to very large database management system caches will be of great concern in commercial applications. How can these concerns be addressed with minimal impact on the performance advantage of object database management?\u0000There appear to be two distinct approaches to object query languages: extensions to SQL and programming language extensions. SQL extensions might provide a fast path to a standard, but would have the traditional impedance mismatch problems associated with embedded query languages. Language extensions are elegant in that they use the same syntax as the programming language and do not suffer from impedance mismatch problems. However, language extensions would probably make standards more difficult to arrive at as it would require the coordination of extensions to multiple languages. Which of the approaches is most appropriate? In which order should these two approaches be addressed by the object database vendors and standards bodies?\u0000One might argue that a good deal of research in relational theory has had little or no impact on commercial relational systems (e.g., relational dependence theory). From a vendor's perspective, what are the hard, interesting research issues whose resolution would allow you to build better systems?","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127132679","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}
This paper considers the garbage collection of concurrent objects for which it is necessary to know not only “reachability,” the usual criterion for reclaiming data, but also the “state” (active or blocked) of the object. For the actor model, a more comprehensive definition than previously available is given for reclaimable actors. Two garbage collection algorithms, implementing a set of “coloring” rules, are presented and their computational complexity is analyzed. Extensions are briefly described to allow incremental, concurrent, distributed and real-time collection. It is argued that the techniques used for the actor model applies to other object-based concurrent models.
{"title":"Garbage collection of actors","authors":"D. Kafura, Douglas Washabaugh, J. Nelson","doi":"10.1145/97945.97961","DOIUrl":"https://doi.org/10.1145/97945.97961","url":null,"abstract":"This paper considers the garbage collection of concurrent objects for which it is necessary to know not only “reachability,” the usual criterion for reclaiming data, but also the “state” (active or blocked) of the object. For the actor model, a more comprehensive definition than previously available is given for reclaimable actors. Two garbage collection algorithms, implementing a set of “coloring” rules, are presented and their computational complexity is analyzed. Extensions are briefly described to allow incremental, concurrent, distributed and real-time collection. It is argued that the techniques used for the actor model applies to other object-based concurrent models.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129153975","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}
Queries in object-oriented databases can return non-homogeneous sets of objects when no type restrictions are placed on the inputs to the query. The tradition has been to force homogeneity on the result by restricting the types of the inputs. This restricts the range of permissible, and possibly useful, queries. We propose a type consistency theory for queries in object-oriented databases which supports the existence of multiple types in the query result. The technique is illustrated by developing type inference rules for an object algebra. The main result is that the loss of type information associated with a query operation is reduced in most cases. We also show how type information is increased when queries are qualified by conjunctive predicates.
{"title":"Type consistency of queries in an object-oriented database system","authors":"D. Straube, M. Tamer Özsu","doi":"10.1145/97945.97971","DOIUrl":"https://doi.org/10.1145/97945.97971","url":null,"abstract":"Queries in object-oriented databases can return non-homogeneous sets of objects when no type restrictions are placed on the inputs to the query. The tradition has been to force homogeneity on the result by restricting the types of the inputs. This restricts the range of permissible, and possibly useful, queries. We propose a type consistency theory for queries in object-oriented databases which supports the existence of multiple types in the query result. The technique is illustrated by developing type inference rules for an object algebra. The main result is that the loss of type information associated with a query operation is reduced in most cases. We also show how type information is increased when queries are qualified by conjunctive predicates.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125944606","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}
This paper describes design issues encountered developing a reusable component library. The design applied encapsulation, inheritance, composition and type parameterization. The implementation uses various C++ mechanisms, including: virtual and static member functions, templates, and exceptions. The resulting library contains about 500 components (mostly template classes and functions) and an optional utility for instantiating templates. The components provide variations of basic collection/container abstractions with various time and space complexities. A key insight gained from this project: the design process centered on developing a “template for the templates” — designing a component framework and orderly process for generating the template classes.
{"title":"The design of the C++ Booch Components","authors":"G. Booch, M. Vilot","doi":"10.1145/97945.97947","DOIUrl":"https://doi.org/10.1145/97945.97947","url":null,"abstract":"This paper describes design issues encountered developing a reusable component library. The design applied encapsulation, inheritance, composition and type parameterization. The implementation uses various C++ mechanisms, including: virtual and static member functions, templates, and exceptions.\u0000The resulting library contains about 500 components (mostly template classes and functions) and an optional utility for instantiating templates. The components provide variations of basic collection/container abstractions with various time and space complexities.\u0000A key insight gained from this project: the design process centered on developing a “template for the templates” — designing a component framework and orderly process for generating the template classes.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123370340","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}
As object oriented techniques enable the fabrication of ever more sophisticated systems, the need grows for a mechanism to ensure the consistent and 'correct' behaviour of each object at run-time. We describe a new, in-source specification mechanism, Message Pattern Specifications (MPS), to directly satisfy this need in a succinct, orthogonal and disciplined manner. Targeted for use in parallel object oriented systems, MPS allows programmers to enunciate the 'legal' patterns of run-time behaviour in which their objects may engage. Furthermore, it supports the definition of methods for object recovery or graceful failure in case these specifications are violated during execution.
{"title":"Message pattern specifications: a new technique for handling errors in parallel object oriented systems","authors":"Jan A. Purchase, R. Winder","doi":"10.1145/97945.97960","DOIUrl":"https://doi.org/10.1145/97945.97960","url":null,"abstract":"As object oriented techniques enable the fabrication of ever more sophisticated systems, the need grows for a mechanism to ensure the consistent and 'correct' behaviour of each object at run-time. We describe a new, in-source specification mechanism, Message Pattern Specifications (MPS), to directly satisfy this need in a succinct, orthogonal and disciplined manner. Targeted for use in parallel object oriented systems, MPS allows programmers to enunciate the 'legal' patterns of run-time behaviour in which their objects may engage. Furthermore, it supports the definition of methods for object recovery or graceful failure in case these specifications are violated during execution.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114685773","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}
Programmers informally reason about object-oriented programs by using subtype relationships to classify the behavior of objects of different types and by letting supertypes stand for all their subtypes. We describe formal specification and verification techniques for such programs that mimic these informal ideas. Our techniques are modular and extend standard techniques for reasoning about programs that use abstract data types. Semantic restrictions on subtype relationships guarantee the soundness of these techniques.
{"title":"Reasoning about object-oriented programs that use subtypes","authors":"Gary T. Leavens, W. Weihl","doi":"10.1145/97945.97970","DOIUrl":"https://doi.org/10.1145/97945.97970","url":null,"abstract":"Programmers informally reason about object-oriented programs by using subtype relationships to classify the behavior of objects of different types and by letting supertypes stand for all their subtypes. We describe formal specification and verification techniques for such programs that mimic these informal ideas. Our techniques are modular and extend standard techniques for reasoning about programs that use abstract data types. Semantic restrictions on subtype relationships guarantee the soundness of these techniques.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115049131","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}
We propose a new object-oriented programming language called RTC++ for programming real-time applications. RTC++ is an extension of C++ and its features are to specify i) a real-time object which is an active entity, ii) timing constraints in an operation as well as in statements, and iii) a periodic task with rigid timing constraints. In this paper, we first discuss real-time programming issues and what language support should be provided for building real-time applications. Then, the key features of RTC++ are described. Some programming examples are shown to demonstrate RTC++'s expressive power. A comparison to other programming languages are also discussed.
{"title":"Object-oriented real-time language design: constructs for timing constraints","authors":"Y. Ishikawa, H. Tokuda, C. W. Mercer","doi":"10.1145/97945.97980","DOIUrl":"https://doi.org/10.1145/97945.97980","url":null,"abstract":"We propose a new object-oriented programming language called RTC++ for programming real-time applications. RTC++ is an extension of C++ and its features are to specify i) a real-time object which is an active entity, ii) timing constraints in an operation as well as in statements, and iii) a periodic task with rigid timing constraints.\u0000In this paper, we first discuss real-time programming issues and what language support should be provided for building real-time applications. Then, the key features of RTC++ are described. Some programming examples are shown to demonstrate RTC++'s expressive power. A comparison to other programming languages are also discussed.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114525791","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}
The paper presents a discussion and a specification of an exception handling system dedicated to object-oriented programming. We show how a full object-oriented representation of exceptions and of protocols to handle them, using meta-classes, makes the system powerful as well as extendible and solves many classical exception handling issues. We explain the interest for object-oriented programming of handlers attached to classes and to expressions. We propose an original algorithm for propagating exceptions along the invocation chain which takes into account, at each stack level, both kind of handlers. Any class can control which exceptions will be propagated out of its methods; any method can provide context-dependant answers to exceptional events. The whole specification and some keys of our Smalltalk implementation are presented in the paper.
{"title":"Exception handling and object-oriented programming: towards a synthesis","authors":"C. Dony","doi":"10.1145/97945.97984","DOIUrl":"https://doi.org/10.1145/97945.97984","url":null,"abstract":"The paper presents a discussion and a specification of an exception handling system dedicated to object-oriented programming. We show how a full object-oriented representation of exceptions and of protocols to handle them, using meta-classes, makes the system powerful as well as extendible and solves many classical exception handling issues. We explain the interest for object-oriented programming of handlers attached to classes and to expressions. We propose an original algorithm for propagating exceptions along the invocation chain which takes into account, at each stack level, both kind of handlers. Any class can control which exceptions will be propagated out of its methods; any method can provide context-dependant answers to exceptional events. The whole specification and some keys of our Smalltalk implementation are presented in the paper.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128197253","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}
Following our own experience developing a concurrent object-oriented language as well of that of other researchers, we have identified several key problems in the design of a concurrency model compatible with the mechanisms of object-oriented programming. We propose an approach to language design in which an executable notation describing the behaviour of communicating agents is extended by syntactic patterns that encapsulate language constructs. We indicate how various language models can be accommodated, and how mechanisms such as inheritance can be modeled. Finally, we introduce a new notion of types that characterizes concurrent objects in terms of their externally visible behaviour.
{"title":"Viewing object as patterns of communicating agents","authors":"Oscar Nierstrasz, M. Papathomas","doi":"10.1145/97945.97952","DOIUrl":"https://doi.org/10.1145/97945.97952","url":null,"abstract":"Following our own experience developing a concurrent object-oriented language as well of that of other researchers, we have identified several key problems in the design of a concurrency model compatible with the mechanisms of object-oriented programming. We propose an approach to language design in which an executable notation describing the behaviour of communicating agents is extended by syntactic patterns that encapsulate language constructs. We indicate how various language models can be accommodated, and how mechanisms such as inheritance can be modeled. Finally, we introduce a new notion of types that characterizes concurrent objects in terms of their externally visible behaviour.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132128627","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}
This paper shows that inheritance and subtyping can be introduced advantageously into a parallel object-oriented language, POOL-I. These concepts are clearly distinguished, because they deal with different aspects of programming. In this way several problems traditionally adhering to inheritance can be solved. The language POOL-I is a parallel object-oriented language with a strong typing scheme which includes genericity and dynamic binding. A novel and particularly powerful mechanism offers the possibility to manipulate and analyse types dynamically.
{"title":"A parallel object-oriented language with inheritance and subtyping","authors":"P. America, F. V. D. Linden","doi":"10.1145/97945.97966","DOIUrl":"https://doi.org/10.1145/97945.97966","url":null,"abstract":"This paper shows that inheritance and subtyping can be introduced advantageously into a parallel object-oriented language, POOL-I. These concepts are clearly distinguished, because they deal with different aspects of programming. In this way several problems traditionally adhering to inheritance can be solved. The language POOL-I is a parallel object-oriented language with a strong typing scheme which includes genericity and dynamic binding. A novel and particularly powerful mechanism offers the possibility to manipulate and analyse types dynamically.","PeriodicalId":135062,"journal":{"name":"OOPSLA/ECOOP '90","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127601171","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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