B. Liskov, Preliminary design of the Thor Object-Oriented Database System, Programming Methodology Group Memo 74, Laboratory of Computer Science, MIT, 92  Home/Search   Document Not in Database   Summary   Related Articles   Check

....in operating systems as well as in programming languages and databases. One emerging model for the support of cooperative distributed applications is that of a distributed shared universe organized as a set of passive objects (active agents are define outside of objects) Bal 92] Dasgupta 90] Liskov 92] In this paper we report on our experience in designing, implementing, and using a system to support such a model. Our goal is to provide an efficient platform for a family of object oriented languages such as Guide (a language designed by our group [Krakowiak 90] and a persistent extension of ....

B. Liskov, Preliminary design of the Thor Object-Oriented Database System, Programming Methodology Group Memo 74, Laboratory of Computer Science, MIT, 92

....Existing work. Certainly, locality exploiting data management has been actively discussed in the context of parallel architectures [ACJ 91, D 89, John92] and compilers [LW91, LW92, Coop92] as well in more general context of data organization, say, in a distributed object store [Lisk92, RD90, Stam84, LMW91, PZ91] distributed databases and services in computer networks. The amount of work on the subject in the systems community is overwhelming. For example, the 1981 survey paper by Dowdy and Foster [DF82] and 1990 survey paper by Gavish and Sheng [GS90] dealing with the file ....

Barbara Liskov. Preliminary design of the thor object-oriented database system. In DARPA Software Technology Conference, pages 50--62, april 1992.

....programs or in programs developed by many people. I believe that subtype polymorphism is a useful program development idea. If CLU were being designed today, I would probably try to include it. I am doing such a design in my current research on an object oriented database system called Thor [Liskov, 1992]. The work on CLU, and other related work such as that on Alphard, served to crystallize the idea of a data abstraction and make it precise. As a result, the notion is widely used as an organizing principle in program design and has become a cornerstone of modern programming methodology. ....

Liskov, Barbara, Preliminary Design of the Thor Object-Oriented Database System, Programming Methodology Group Memo 74, MIT Laboratory for Computer Science, Cambridge, MA, March 1992.

....for which clients expect continuous operation despite faults and transmission delays. So, though originally motivated to support distributed file systems, weak sets are more generally abstractions useful for both persistent object repositories, e.g. Cricket [14] EOS [5] Gemstone [10] and Thor [8] (see [1] for others) and wide area information systems and their applications, e.g. the World Wide Web (WWW) 2] WAIS [7] and Gopher[11] Using an iterator like operation to perform search and retrieval is common in these systems. 1.3 Roadmap The rest of the paper is structured as follows: ....

B. Liskov. Preliminary design of the Thor object-oriented database system. In Proc. of the Software Technology Conference. DARPA, April 1992.

....1. 4 Our Results versus Previous Work Locality exploiting data management has been actively discussed in the context of parallel architectures [ACJ 91, D 89, Joh92] and compilers [ML91, LW92, Coo92] as well in more general context of data organization, say, in a distributed object store [Lis92, RD90, Sta84, WLG91, PZ91] distributed databases and services in computer networks [DF82, ML88] etc. The amount of work on the subject in the systems community is overwhelming. For example, the 1981 survey paper by Dowdy and Foster [DF82] dealing with the file allocation (or assignment) ....

Barbara Liskov. Preliminary design of the thor object-oriented database system. In DARPA Software Technology Conference, pages 50--62, april 1992.

....in operating systems as well as in programming languages and databases. One emerging model for the support of co operative distributed applications is that of a distributed shared universe organized as a set of passive objects (active agents are define outside of objects) Bal 92] Dasgupta 90] Liskov 92] In this paper we report on our experience in designing, implementing, and using a system to support such a model. Our goal is to provide an efficient platform for a family of objectoriented languages such as Guide (a language designed by our group [Krakowiak 90] and a persistent extension of ....

B. Liskov, Preliminary design of the Thor Object-Oriented Database System , Programming Methodology Group Memo 74, Laboratory of Computer Science, MIT, 92

....object is accessed via x. To reason about the use of variable x using the specification of its type , we need to impose additional constraints on the subtype relation. Now consider the case of an environment of shared mutable objects, such as is provided by object oriented databases (e.g. Thor [Liskov 1992] and Gemstone [Maier and Stein 1990] In fact, it was our interest in Thor that motivated us to study the meaning of the subtype relation in the first place. In such systems, there is a universe containing shared, mutable objects and a way of naming those objects. In general, lifetimes of ....

....the only interesting part is the definition of the abstraction function; the other parts of the proof are usually trivial. However, this section goes through the steps of an informal proof just to show what kind of reasoning is involved. Formal versions of these informal proofs are given in [Liskov and Wing 1992]. Let s revisit the stack and bag example using our definition as a checklist. Here oe = hO stack ; S; fpush; pop; swap top; height; equalgi, and = hO bag ; B; fput; get; card; equalgi. Recall that we represent a bounded bag s value as a pair, helems; boundi, of a multiset of integers and a ....

Liskov, B. 1992. Preliminary design of the Thor object-oriented database system. In Proc. of the Software Technology Conference. DARPA. Also Programming Methodology Group Memo 74, MIT Laboratory for Computer Science, Cambridge, MA, March 1992.

....object is accessed via x. To reason about the use of variable x using the specification of its type , we need to impose additional constraints on the subtype relation. Now consider the case of an environment of shared mutable objects, such as is provided by object oriented databases (e.g. Thor [26] and Gemstone [29] In fact, it was our interest in Thor that motivated us to study the meaning of the subtype relation in the first place. In such systems, there is a universe containing shared, mutable objects and a way of naming those objects. In general, lifetimes of objects may be longer ....

B. Liskov. Preliminary design of the thor object-oriented database system. In Proc. of the Software Technology Conference. DARPA, April 1992. Also Programming Methodology Group Memo 74, MIT Laboratory for Computer Science, Cambridge, MA, March 1992.

....is accessed via x. To reason about the use of variable x using the specification of its type , we need to impose additional constraints on the subtype relation. Now consider the case of an environment of shared mutable objects, such as is provided by object oriented databases (e.g. Thor [Lis92] and Gemstone [MS90] In such systems, there is a universe containing shared, mutable objects and a way of naming those objects. In general, lifetimes of objects may be longer than the programs that create and access them (i.e. objects might be persistent) and users (or programs) may access ....

Liskov, B. Preliminary design of the Thor object-oriented database system. In Proc. of the Software Technology Conference. DARPA, April 1992. Also Programming Methodology Group Memo 74, MIT Laboratory for Computer Science, Cambridge, MA, March 1992.

....Chapter 3 An Overview of Thor Thor is an object oriented database system being developed by the Programming Methodology Group at the Laboratory for Computer Science at MIT. Thor can be used in a heterogenous distributed system and it allows programs written in different languages to share objects [Lis92, LDS92]. This chapter describes the system architecture of Thor, but the description is restricted to what is relevant to the design proposed in this thesis. The setting and the terminology introduced herein will be assumed in later chapters. The nodes that run client programs are different from server ....

B. Liskov. Preliminary Design of the Thor Object-Oriented Database System. Programming Methodology Group Memo 74, MIT Laboratory for Computer Science, Mar 1992.

....our algorithm and compares it to other work on optimistic concurrency control. Section 4 compares our performance to adaptive callback locking. We conclude with a discussion of what we have accomplished. 2 The Environment Our work has been done in the context of the Thor objectoriented database [21, 22]. Thor allows user applications to share a universe of persistent objects. Objects are encapsulated for safe sharing, and applications access them by invoking methods that observe or modify their object s state. Application computations occur within transactions so that persistent objects can be ....

B. Liskov. Preliminary Design of the Thor Object-Oriented Database System. Programming Methodology Memo 74, MIT Lab. for Computer Science, March 1992.

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