S. Abiteboul, P.C. Kanellakis, and E. Waller. Method schemas. In Proceedings 9th ACM Symposium on Principles of Database Systems, pages 16--27. ACM Press, 1990.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....namely O 2 Views [SdS95] 1 From the outset, our view specification mechanism is independent of any particular programming model. Yet, in order to be able to concretely assess the ramifications of our mechanism, we have implemented it on top of the formalism of method schemas. Method schemas ([AKW90, AKRW95]; see also [AH95, HKR94, Wal91] provide a formalization of object oriented database programming using methods, in much the same way that the classical formalism of program schemes [Cou90] does for classical programming. In this concrete context, we then explore the various correctness issues ....

S. Abiteboul, P.C. Kanellakis, and E. Waller. Method schemas. In Proceedings 9th ACM Symposium on Principles of Database Systems, pages 16--27. ACM Press, 1990.

....knowledge that allows static type checking of covariant code. In particular, this prevents passing bounded parameters to another function. Finally, F bounded quantification [CCHO89] allows to support recursively defined types, like P erson and Student in Figure 1. In the works on method schemas [AKW90, Wal91] no consistency rules are imposed on the schema and the return type of user defined methods is not specified. Consistency is defined as type safety, i.e. absence of run time type errors. Proving type safety involves simulating the execution of methods from a typing point of view. This is ....

S. Abiteboul, P. Kanellakis, and E. Waller. Method schemas. In Proceedings of the fourth ACM Symposium on the Principles of Database Systems, Nashville, MA, April 1990.

....of methods associated to the classes. Those aspects are outside the scope of our investigations. Nevertheless, we argue that general techniques for schema level reasoning, in particular, type consistency and type inference, can be pro tably exploited for restricted forms of reasoning on methods (Abiteboul, Kanellakis, Ramaswamy, Waller, 1992). 5.1 Syntax of an Object Oriented Model Below we de ne a simple object oriented language in the style of most popular models featuring complex objects and object identity. Although we do not refer to any speci c formalism, our model is inspired by the ones presented by Abiteboul and Kanellakis ....

Abiteboul, S., Kanellakis, P., Ramaswamy, S., & Waller, E. (1992). Method schemas. Tech. rep. CS-92-33, Brown University. An earlier version appeared in Proc. of the 9th Symp. on Principles of Database Systems PODS-90.

....Laboratory under Contract F30602 92 C 0140. for example work by Maier on O logic [26] work by Kifer and Lausen on F logic [23] work by Goguen, Meseguer and Wolfram on the FOOPS language [17, 21] work by Beeri and Milo on algebraic foundations [8, 9, 10] and work by Abiteboul on method schemas [4, 3] (see [23, 9] for additional references in this whole area) However, it seems fair to say that no agreement has yet been reached on the matter of foundations, and that many problems remain open as serious challenges, especially in dynamic aspects having to do with evolution in time and state ....

....the paper with some concluding remarks about directions for future work. Behavioral Aspects Beeri [9] has commented that behavioral aspects have not been considered in depth by the database theory community. Initial efforts in this area include the work on F Logic [23] and work on method schemas [3, 4], which uses a form of graph rewriting. In MaudeLog, type structure and behavior are fully integrated in an implementation independent way. The type structure is made up of user definable algebraic data types, object classes (with objects having attributes and being queried and updated by ....

S. Abiteboul, P. Kanellakis, and E. Waller. Method schemas. In Proc. 9th PODS, pages 16--27. ACM, 1990.

....view the components of an object oriented schema are highly interdependent. This need for a formal basis was also seen by other researchers like Abiteboul, Kanellakis, and Waller who defined a minimal formal model which allows to reason about formal proper1 ties of schemas and schema updates [1, 22]. Nevertheless, our intention in formalizing the notion of schema consistency is somewhat different. Since their notion of schema consistency based on a rewrite approach is quite general, it allows to state undecidable notions of consistency. Although also looking for some possibility to formally ....

S. Abiteboul, P. Kanellakis, and E. Waller. Method schemas. In PODS, pages 16--27, 1990.

....u under S, and a term to be verified, the detection problem of security flaws is to decide whether u can infer the value of under S, I , and A. The main aim of this paper is to show an efficient algorithm for the detection problem of security flaws. We adopt method schemas proposed by [1] [2] as a formal model of OODB schemas since they have such basic features of OODBs as method overloading, dynamic binding, and complex objects. The semantics is simply defined based on term rewriting. We show that, in this formalization, the problem is reduced to the congruence closure problem ....

....method definition states that the application of m u to o 1 , o 2 , on results in term rewriting starting from t[o 1 =x 1 ; o 2 =x 2 ; on =xn ] The formal definition is presented in Sect. 2.3. Definition 3: A method schema, which is originally introduced by Abiteboul et al. 1] [2], is a 5 tuple (C; M; 6 b ; 6 u ) as follows: 1. C is a finite set of class names. 2. is a partial order representing a class hierarchy. When c 0 = c, we say that c 0 is a subclass of c and c is a superclass of c 0 . 3. M is a method signature. 4. 6 b is a set of base method ....

[Article contains additional citation context not shown here]

S. Abiteboul, P. Kanellakis, S. Ramaswamy and E. Waller, "Method schemas," J. Computer and System Sci., Vol.51, No.3, pp.433--455, 1995.

....the elements of the set. Consequently, if we allow to update objects that are not identified by the set expression itself, we have to cope with object sharing. Otherwise, we have to restrict the update operations. In object oriented models, updates are usually carried out by applying methods (see [3, 6]) That is, integrity preserving updates are offered to clients. In most object oriented models (see e.g. 8, 14, 21] these updates are built upon predefined C or Smalltalk m n upd 1 n upd m 1 upd 1 1 upd thread 1 thread n ; state a state b Figure 1: Transformation of state a to b by ....

S. Abiteboul, P.C. Kanellakis, and E. Waller. Method schemas. In Proc. ACM PODS, Nashville, TN, April 1990.

....cut x 0 f (x 0 :f Gamma (x 0 :f : M M ) This modification is of course not mandatory, the programmer could have migrated the objects into another class. Our aim is just to decide whether a program is consistent or not. 3 Preliminaries Data Model We recall briefly the model defined in [AKW90] without methods, and that we extend with sets. We assume the existence of the following disjoint countable sets of class names fc 1 ; c 2 ; g and attribute names fa 1 ; a 2 ; g (simply called classes and attributes in the following) A signature is an expression c c 0 or c fc 0 g, ....

S. Abiteboul, P. Kanellakis, and E. Waller. Method schemas. In PODS, pages 16--27, 1990.

....to update revision of knowledge bases appear in [Bor85, Dal88, Sat88, Win88] Now the computational problem appears: can we do this efficiently In general, we show the problem to be Co NP Complete in the size of the database instance. But for an important class of schemas, the covariant schemas [AKW90], we give a linear time algorithm. We introduce different distance measurements and show how they can be used to control the adaptation process. We study the relationship between adaptation techniques based on different distance measurements. In particular we show that for covariant schemas some ....

....The effect of adaptation on method execution is studied in section 7. Possible extensions and applications of the techniques are considered in section 8. Finally, conclusions are presented in section 9. 2 Preliminaries In this section we briefly introduce the data model. We use the data model of [AKW90], extended with set values. The presentation below is rather informal. For formal definition see [AKW90] We use in this work a specific data model, but the results can be easily adapted to other object oriented data models. We have an isa hierarchy of classes fC; g, where each class represents ....

[Article contains additional citation context not shown here]

S. Abiteboul, P. Kanellakis, and E. Waller. Method schemas. In Proc. 9th Symp. on Principles of Database Systems - PODS, pages 16--27, 1990.

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC