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subquery approach
Decision Support Systems Reports and Theses: Abstracts
there are at most q,,(n) many states over A,, on which a executes different sequences of instructions; there are at most ra(n) many prefixes generated by computations of a over A,,. These results give a new proof of a theorem used in Berman, Halpern and Tiuryn (On the power of nondeterminism in dynamic logic, in AUTOMATA, LANGUAGES and PROGRAMMING, 1982), which is straightforward and easy to understand. As a further corollary we show that the standard function pop on A can be computed by a deterministic program over A, but not by one using only polynomial space. Author's Abstract
Laurent Vieme, Recursive Axioms in Deductive Databases: The Query / Subquery Approach.. European Computer-lndustry Research Center, Muenchen, FRG, April 1986. This paper proposes a method for handling recursive axioms is deductive databases which applies for any kind of recursion defined by means of function-free Horn clauses. Its main features are that it always terminates while guaranteeeing answer completeness; it restricts accesses to those basic facts which are effectively needed for answeri,$, the query (by means of an appropriate constant propagation scheme); i t makes use of conventional database techniques for fact handling. Two strategies for execution, one iterative and the other one recursive, are proposed for implementation, the recursive strategy appearing to be more appealing. Author's Abstract
Ingrid Walter, Peter C. Lockemann and Hans-HeiImut Nagel, Ein Datenmodellenentwurf fuer die Extraktion yon Episedeu aus Bildlolgen, Fakultaet fuer Infonnatik, Universitaet Karlsruhe, FRG, Februar 1986. In the process of analysing image sequences on the episode level of abstraction, several kinds of data arise: data describing (static) physical objects, data describing (dynamic) simple activities and complex activities, i.e. episodes, and data describing and controlling the extraction process. Based on an analysis of the relationships within
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these groups of data and between the groups, a structure for an episode extraction system is developed. The description of objects and of activities relies on knowledge representation techniques, in particular KL-ONE. The extraction process uses augmented transition networks (ATN). Some necessary extensions of conventional data models are discussed. Author's Abstract
Ingrid Walter, Peter C. Lockemann and Hans.Hellmut Nagel, Untersuehung von DatenbankSchemata zur Modellierung yon Episoden bei der algoritlunischen Deutung von Bildfolgen, Fakultaet fuel" Informatik, Universitaet Karisrueh, FRG, Februar 1986. In the context of analysing image sequences the description of the content on a purely geometrical basis is inadequate for a human observer. Instead, representations on a higher level of abstraction are required. The notion of an episode seems to provide an appropriate level of abstraction. This report develops some characteristic features of episodes starting from a time measurement system. Further it points out a relationship between episodes and entries within a hierarchy of verb concepts. In consideration of this relationship, representation techniques used in natural language processing are investigated with respect to their suitability for episodes. Author's Abstract
Ouri Wolfson, Overhead of Locking Protocols in a Distributed Database, TECItNION - Israel Institute of Technology, Department of Computer Science; Haifa, Israel, November 1985. The main purpose of a locking protocol is to ensure correct interleaving of actions executed by different transactions. The locking protocol consists of a set of rules dictating how accessed entities should be locked and unlocked. As a result of obeying the rules the transactions incur an overhead, particularly in a distributed database. We propose three measures for evaluating this overhead, each most suitable to a different type of underlying communication network. Then we analyze and compare three protocols according to
there are at most q,,(n) many states over A,, on which a executes different sequences of instructions; there are at most ra(n) many prefixes generated by computations of a over A,,. These results give a new proof of a theorem used in Berman, Halpern and Tiuryn (On the power of nondeterminism in dynamic logic, in AUTOMATA, LANGUAGES and PROGRAMMING, 1982), which is straightforward and easy to understand. As a further corollary we show that the standard function pop on A can be computed by a deterministic program over A, but not by one using only polynomial space. Author's Abstract
Laurent Vieme, Recursive Axioms in Deductive Databases: The Query / Subquery Approach.. European Computer-lndustry Research Center, Muenchen, FRG, April 1986. This paper proposes a method for handling recursive axioms is deductive databases which applies for any kind of recursion defined by means of function-free Horn clauses. Its main features are that it always terminates while guaranteeeing answer completeness; it restricts accesses to those basic facts which are effectively needed for answeri,$, the query (by means of an appropriate constant propagation scheme); i t makes use of conventional database techniques for fact handling. Two strategies for execution, one iterative and the other one recursive, are proposed for implementation, the recursive strategy appearing to be more appealing. Author's Abstract
Ingrid Walter, Peter C. Lockemann and Hans-HeiImut Nagel, Ein Datenmodellenentwurf fuer die Extraktion yon Episedeu aus Bildlolgen, Fakultaet fuer Infonnatik, Universitaet Karlsruhe, FRG, Februar 1986. In the process of analysing image sequences on the episode level of abstraction, several kinds of data arise: data describing (static) physical objects, data describing (dynamic) simple activities and complex activities, i.e. episodes, and data describing and controlling the extraction process. Based on an analysis of the relationships within
281
these groups of data and between the groups, a structure for an episode extraction system is developed. The description of objects and of activities relies on knowledge representation techniques, in particular KL-ONE. The extraction process uses augmented transition networks (ATN). Some necessary extensions of conventional data models are discussed. Author's Abstract
Ingrid Walter, Peter C. Lockemann and Hans.Hellmut Nagel, Untersuehung von DatenbankSchemata zur Modellierung yon Episoden bei der algoritlunischen Deutung von Bildfolgen, Fakultaet fuel" Informatik, Universitaet Karisrueh, FRG, Februar 1986. In the context of analysing image sequences the description of the content on a purely geometrical basis is inadequate for a human observer. Instead, representations on a higher level of abstraction are required. The notion of an episode seems to provide an appropriate level of abstraction. This report develops some characteristic features of episodes starting from a time measurement system. Further it points out a relationship between episodes and entries within a hierarchy of verb concepts. In consideration of this relationship, representation techniques used in natural language processing are investigated with respect to their suitability for episodes. Author's Abstract
Ouri Wolfson, Overhead of Locking Protocols in a Distributed Database, TECItNION - Israel Institute of Technology, Department of Computer Science; Haifa, Israel, November 1985. The main purpose of a locking protocol is to ensure correct interleaving of actions executed by different transactions. The locking protocol consists of a set of rules dictating how accessed entities should be locked and unlocked. As a result of obeying the rules the transactions incur an overhead, particularly in a distributed database. We propose three measures for evaluating this overhead, each most suitable to a different type of underlying communication network. Then we analyze and compare three protocols according to