Showing papers by "French Institute for Research in Computer Science and Automation published in 1980"
TL;DR: This paper gives new results, and presents old ones, concerning ChurchRosser theorems for rewrmng systems, depending solely on axioms for a binary relatton called reduction, and how these criteria yield new methods for the mechanizaUon of equattonal theories.
Abstract: This paper gives new results, and presents old ones m a umfied formahsm, concerning ChurchRosser theorems for rewrmng systems Abstract confluence propentes, depending solely on axioms for a binary relatton called reduction, are first presented Results of Newman and others are presented m a unified formahsm The systemattc use of a powerful mductmn pnnciple permRs the generahzauon of results of Sethl on reduction modulo eqmvalence. Simphficatton systems operating on terms of a first-order logic are then considered. Results by Rosen and Knuth and Bendix are extended to give several new crtteria for confluence of these systems It ts then shown how these criteria yield new methods for the mechanizaUon of equattonal theories
1,067 citations
01 Jul 1980
TL;DR: This note discusses the MENTOR program manipulation system, from the following points of view: the main design decisions made in MENTor; the authors' experience with building and using a PASCAL programming environment based on MENTSOR; and the authors's vision of a complete programming environment.
Abstract: : This note discusses the MENTOR program manipulation system, from the following points of view: the main design decisions made in MENTOR; the authors' experience with building and using a PASCAL programming environment based on MENTOR; and the authors' vision of a complete programming environment.
206 citations
TL;DR: A single-server processor-sharing system with M job classes is analyzed in the steady state and new expressions for the conditional expected response times Wk(t) of class k jobs with required service time t are obtained and the unconditional average response times are obtained.
Abstract: . A single-server processor-sharing system with M job classes is analyzed in the steady state. The scheduling strategy considered divides the total processor capacity in unequal fractions among the different job classes. More precisely, if there are N~jobs of classj in the system, j = 1, 2 ..... M, each class k job receives a fraction gh/(~M.~ giN~) of the processor capacity. Earlier analyses of this system are shown to be incorrect and new expressions for the conditional expected response times Wk(t) of class k jobs with required service time t are obtained (for general required service time distributions). These yield the asymptotic behavior of W~(t) as t ~ oo and rather simple formulas in the exponential case. The unconditional average response times are also obtained. KEY WORDS AND PHRASES: processor sharing, strategy, egalitarian, discriminatory job classes, Laplace transform, Fourier-Stiehjes transform CR CATEGORIES: 4.35.4.6, 5.5, 6.2
194 citations
28 Apr 1980
TL;DR: The isomorphism problem for graphs has been in recent years the object of a much research and it is not known whether there exists a polynomial-time algorithm for it.
Abstract: The isomorphism problem for graphs has been in recent years the object of a much research (see e.g. [Col 78] or [Re-Cor 77]). Its complexity is still unknown. It is not known whether the problem is NP-complete, although it is NP, of course. It is not known whether there exists a polynomial-time algorithm for it. Recently, Babai [Ba 79] has discussed probabilistic algorithms. For additional information see also [Mi 77]. The problem has also some practical applications. Of the known algorithms let us only quote the work of Weinberg [We 66] and of Hopcroft and Tarjan [Ho-Ta 72]. Weinberg's algorithm rums in quadratic time (in αo, the number of vertices of the graphs). Hopcroft and Tarjan's runs in time 0(αo logαo) and uses their powerful technique of depth-first search. Both these algorithms apply only to planar (Weinberg's only to 3-connected planar) graphs. They rely on a well-known rigidity theorem of Withney [Withney 32].
125 citations
13 Oct 1980
TL;DR: This work shows how to prove (and disprove) theorems in the initial algebra of an equational variety by a simple extension of the Knuth-Bendix completion algorithm, and applications to proofs of programs computing over data structures, and to algebraic summation identities.
Abstract: We show how to prove (and disprove) theorems in the initial algebra of an equational variety by a simple extension of the Knuth-Bendix completion algorithm. This allows us to prove by purely equational reasoning theorems whose proof usually requires induction. We show applications of this method to proofs of programs computing over data structures, and to proofs of algebraic summation identities. This work extends and simplifies recent results of Musser15 and Goguen6.
105 citations
TL;DR: A framework for the quantitative analysis of the impact of these factors on the performance of DBMS is presented and the main factors which determine the behavior of these systems are pointed out and analyzed independently and aggregated to yield a global performance evaluation.
Abstract: Consistency control has to be enforced in database management systems (DBMS) where several transactions may concurrently access the database. This control is usually achieved by dividing the database into locking units or granules, and by specifying a locking policy which ensures integrity of the information. However, a drawback of integrity enforcement through locking policies is the degradation of the global system performance. This is mainly due to the restriction imposed by the locking policies to the access of transactions to the database, and to the overheads involved with the management of locks. A framework for the quantitative analysis of the impact of these factors on the performance of DBMS is presented in this paper. In a first step, the main factors which determine the behavior of these systems are pointed out and analyzed independently. The results hereby obtained are aggregated in a second step to yield a global performance evaluation. Throughout this hierarchical modeling approach various analytical techniques are used and the results are illustrated by numerical examples. The paper concludes by pointing out the final results' sensitivity to some basic assumptions concerning transaction behavior and the need for more experimental studies in this area.
87 citations
01 Jan 1980
TL;DR: In this paper, the authors studied nonlinear shallow shell problems with pseudo-monotone operalors and proved that solutions of these problems arc unique whenever the loads are sufficiently large.
Abstract: ABSTRM'I. This work is devoted to the analysis of a class of nonlinear shallow shell problems. First we recall the classical nonlinear shallow shell equations of W. T. Koiter b'lsed on a representation of the middle surface of the shell by a general system of curvilinear coordinates. Next. we prove an e~istencc Theorem for solutions of these equations using the theory of pseudo,monotone operalors. Finally. we prove that solutions arc unique whenever the loads are sufficiently sm.1l1. Existence '\J1d uniqueness resulls for Ihe nonlinear theory of plates are reduced as u special case from our theory.
31 citations
14 May 1980
TL;DR: It is shown that an automaton-like device is sufficient to perform projections and restrictions of relations and insertions, deletions and updates of tuples and to structure the n-ary relations into hierarchical free format files.
Abstract: Most data base machines use some type of "filter" to perform unary operations on files. This filter processes information "on the fly" during its transfer from mass storage (Disk) to main storage (main memory or buffer). This paper is devoted to the design study of such a filter for relational-type data bases. It is therefore assumed that data are structured as a set of n-ary relations.Using a top-down approach we classify the requirements under two catagories:1) Functional specification of the filter: the filter should perform the unary relational operations i.e. projection and restriction; it should also permit insertion deletion and updates of tuples.2) Performance requirements: in a filtering system access time is a linear function of the space used to the store relations, it becomes therefore of the utmost importance to minimize this space.In order to meet the second requirement, we suggest to structure the n-ary relations into hierarchical free format files. Clearly, such a data structure minimizes space: the remaining problems being the ability to read and update such files. It is then shown that an automaton-like device is sufficient to perform projections and restrictions of relations and insertions, deletions and updates of tuples. That device is described and an algorithm that automatically generates the microprogram realizing that device from the description of the relation and that of the operations to be performed is given.
23 citations
14 Jan 1980
TL;DR: This paper presents a method for specifying and proving compilers based on the algebraic data types ideas, which states that to each language is associated an algebraic abstract data type, and the semantic value of a program is given as a term of this data type.
Abstract: This paper presents a method for specifying and proving compilers. This method is based on the algebraic data types ideas. The main points are :
to each language is associated an algebraic abstract data type.
the semantic value of a program is given as a term of this data type.
the translation of the semantic values of source programs into semantic values of target programs is specified and proved as the representation of an algebraic data type by another one.
17 citations
01 Jan 1980
Abstract: Publisher Summary This chapter presents the asymptotic calculus of variations. For the case of problems of optimal control, if one writes the optimality system, one ends up with a problem of singular perturbation, either for partial differential equations, in the case of no constraints, or for variational inequalities. A direct verification is possible for Dirichlet's boundary conditions; however, for general boundary conditions, the best method is the Energy method of L. Tartar. The averaging principle is a particular case of a general conjecture for nonquadratic functional and with constraints. The problem of optimal control (without constraints) is to find inf Jɛ(v), v ɛ L2(Q); it admits a unique solution uɛ: inf Jɛ(v) = Jɛ(uɛ). The asymptotic expansion of in f Jɛ(v ) in this case seems to be an open question. The asymptotic expansion depends on the geometry and more precisely on the position of r with respect to the x1's direction.
9 citations
01 Jan 1980
01 Jan 1980
01 Jan 1980
01 Jan 1980
30 Sep 1980
TL;DR: It is shown this concept can be used to write operating systems and a common base for synchronization and protection expression is sketched.
Abstract: Program structuring relies on data abstraction concept. It is shown this concept can be used to write operating systems; to this end two system aspects are tackled: protection and synchronization. On protection hand some visibility and access control problems, usually solved by dynamic mechanisms, are statically solved by using modules or abstract data type constructs. On synchronization hand some expressions well-suited to module exist but they need extensions to cope with data abstraction mechanism: so an appropriate proposal is made. Finally a common base for synchronization and protection expression is sketched.
14 Apr 1980
TL;DR: This paper investigates the various aspects of data security in a general-purpose Data Base Management System (DBMS) and gives an overview of the potential solutions to each feature.
Abstract: With the ever-increasing use of computers for storing large volumes of vital data, the problems involved in providing data security have been receiving very great attention from researchers. In this paper we try to investigate the various aspects of data security in a general-purpose Data Base Management System (DBMS). Data security concerns data manipulation which encompasses two phases : retrieval and access (read/write). Privacy protection is associated with the retrieval phase and integrity attached to the modification phase. In this paper, we detail both parts of data security and give an overview of the potential solutions to each feature.
01 Jan 1980
TL;DR: In this article, water-oil displacements in porous media are modelized by a system of non linear partial differential equations, one of them is of diffusion-convection type with small diffusion.
Abstract: Water-oil displacements in porous media are modelized by a system of non linear partial differential equations. One of them is of diffusion-convection type with small diffusion. Our numerical model is obtained by means of a discontinuous finite elements method, using an "upwind" scheme for convection terms. Diffusion terms are approximated with a mixed formulation which gives easily water and oil flows. Our method is illustrated by numerical results.
01 Jan 1980
TL;DR: A possible approach to an air-to-air combat problem consists in considering it as a zero-sum game between two aircrafts on a fixed time-interval.
Abstract: A possible approach to an air-to-air combat problem consists in considering it as a zero-sum game between two aircrafts on a fixed time-interval. When one is looking for an open-loop solution, this leads to solving a certain optimal control problem, governed by ordinary differential equations : the state equations are the nonlinear equations describing the flight-mechanics ; the cost function -either final or integral- is evaluated by the relative positions of the aircrafts ; the control variables -pilots' actions- and state variables -aircrafts' positions- are subject to nonlinear constraints, depending on the characteristics of the aircrafts.
01 Jan 1980
TL;DR: In this article, a modele de simulation d'un train de laminage a chaud prenant en compte tous les principaux phenomenes physiques and incluant les regulations existantes is presented.
Abstract: Nous presentons un modele de simulation d'un train de laminage a chaud prenant en compte tous les principaux phenomenes physiques et incluant les regulations existantes. Apres la presentation du modele mathematique, nous indiquons les methodes numeriques utilisees pour la resolution du probleme. Enfin, nous donnons quelques resultats numeriques que nous comparons avec les valeurs reelles mesurees sur le train.