A class of database schemes, called acychc, was recently introduced. It is shown that this class has a number of desirable properties. In particular, several desirable properties that have been studied by other researchers m very different terms are all shown to be eqmvalent to acydicity. In addition, several equivalent charactenzauons of the class m terms of graphs and hypergraphs are given, and a smaple algorithm for determining acychclty is presented. Also given are several eqmvalent characterizations of those sets M of multivalued dependencies such that M is the set of muRlvalued dependencies that are the consequences of a given join dependency. Several characterizations for a conflict-free (in the sense of Lien) set of muluvalued dependencies are provided.

On the Desirability of Acyclic Database Schemes

Presented is a computation method—the chase—for testing implication of data dependencies by a set of data dependencies The chase operates on tableaux similar to those of Aho, Sagiv, and Ullman The chase includes previous tableau computation methods as special cases By interpreting tableaux alternately as mappings or as templates for relations, it is possible to test implication of join dependencies (including multivalued dependencies) and functional dependencies by a set of dependencies

Testing implications of data dependencies

A Protocol Test Generation Procedure.

Definition d'une classe de dependances, dependances generant l'equalite et les triples et generalisation du processus de poursuite pour traiter ces dependances. On montre quelques cas pour lesquels il y a une procedure de decision. Redondance de l'egalite pour decider de l'implication des dependances generant les triples et «presque redondance» pour decider de l'implication des dependances generant l'egalite

A Proof Procedure for Data Dependencies

The goal of this paper is to provide a systematic and unifying introduction to relational database theory, including some of the recent developments in database logic programming. The first part of the presentation covers the two basic components of the relational data model: its specification component, that is the database scheme with dependencies, and its operational component, that is the relational algebra query language. The choice of basic constructs for specifying the semantically meaningful databases and for querying them is justified through an in-depth investigation of their properties. Some important research themes are reviewed in this context: the analysis of the hypergraph syntax of a database scheme and the extensions of the query language using deduction or universal relation assumptions. The subsequent parts of the presentation are structured around the two fundamental concepts illustrated in the first part, dependencies and queries. The main themes of dependency theory are implication problems and applications to database scheme design. Queries are classified in a variety of ways, with emphasis on the connections between the expressibility of query languages, finite model theory and logic programming. The theory of queries is very much related to research on database logic programs, which are an elegant formalism for the study of the principles of knowledge base systems. The optimization of such programs involves both techniques developed for the relational data model and new methods for analyzing recursive definitions. The exposition closes with a discussion of how relational database theory deals with the problems of complex objects, incomplete information and database updates.

Elements of Relational Database Theory.

Recently various real-time communication protocols have been proposed. In this paper, first, we propose a timed I/O automaton model so that we can simply specify such real-time protocols. The proposed model can handle not only time but also data values. Then, we propose a conformance testing method for the model. In order to trace a test sequence (I/O sequence) on the timed I/O automaton model, we need to execute each I/O action in the test sequence at an adequate execution timing which satisfies all timing constraints in the test sequence. However, since outputs are given from IUTs and uncontrollable, we cannot designate their output timing in advance. Also their output timing affects the executable timing for the succeeding I/O actions in the test sequence. Therefore, in general, the executable timing of each input action in a test sequence can be specified by a function of the execution time of the preceding I/O actions. In this paper, we propose an algorithm to decide efficiently whether a given test sequence is executable. We also give an algorithm to derive such a function from an executable test sequence automatically using a technique for solving linear programming problems, and propose a conformance testing method using those algorithms.

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Generating Test Cases for a Timed I/O Automaton Model

Two decision problems related to multivalued dependencies in a relational database are considered In this paper, an algorithm is presented for deciding whether or not a multivalued dependency can be derived from sets F of functional dependencies and M of multivalued dependencies on a set U of attributes, whose running time is proportional to min $(k^2 |U|,||F \cup M||^2 )$ where k and $|U|$ are the numbers of dependencies in $F \cup M$ and attributes in U, respectively, and $||F \cup M||$ is the size of description of F and M A related algorithm is also considered which decides whether or not there exists a nontrivial multivalued dependency that is valid in a projection of the original relation

Decision Problems for Multivalued Dependencies in Relational Databases

In this paper, we propose an automatic test case derivation method for an extended finite state machine model called EFSM/pres where extended UIO sequences called E-UIO sequences are generated. In the EFSM/pres model, each EFSM has a finite control and a finite number of registers where the data types of I/O data and registers’ values are restricted to the integer type. The next registers’ values are represented as linear combinations of the input values and current register values. The transition conditions on input variables and register variables are written using addition, subtraction, comparison and Boolean operators. For such a restricted class, we enumerate every transition sequence and decide whether the sequence is an E-UIO sequence for a given state mechanically. Concrete data values for the E-UIO sequence are also generated mechanically where a decision procedure for Presburger arithmetic is used. The derivation of E-UIO sequences for a part of OSI Session protocol is given as an example.

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Automatic generation of extended UIO sequences for communication protocols in an EFSM model

A result on the equivalence problem for deterministicpushdown automata

In general, the services of a distributed system are provided by some cooperative protocol entities. The protocol entities must exchange some data values and synchronization messages in order to ensure the temporal ordering of the events which are described in a service specification of the distributed system. It is desirable that a correct protocol entity specification for each node can be derived automatically from a given service specification. In this paper, we propose an algorithm which synthesizes a correct protocol entity specification automatically from a service specification in a Petri Net model with Registers called PNR model. In our model, parallel events and selective operations can be described naturally. The control flow of a service specification must be described as a free-choice net in order to simplify the derivation algorithm, however, many practical systems can be described in this class. In our approach, since each protocol entity specification is also described in our PNR model, we can easily understand what events can be executed in parallel at each protocol entity.

Kenichi Taniguchi

Papers

Generating Test Cases for a Timed I/O Automaton Model

Decision Problems for Multivalued Dependencies in Relational Databases

Automatic generation of extended UIO sequences for communication protocols in an EFSM model

A result on the equivalence problem for deterministicpushdown automata

Synthesis of protocol entities specifications from service specifications in a Petri net model with registers