MOD

An algebra which operates on partitioned relations is developed. Relation partitioning is achieved by defining equivalence relations on n-ary relations. It is shown that the algebra is as powerful as the original relational algebra, having the advantage ...

For the extension of high-level languages by data types of mode relation, three language constructs are proposed and discussed:- a repetition statement controlled by relations- predicates as a generalisation of boolean expressions- a constructor for ...

Let R be a relational database containing relations {R₁,R₂,…,R_n}. For each relation R_i, 1 ≤ i ≤ n, let D_i = {d_i,1,d_i,2,…} be its set of domains and let K_i = {k_i,1,k_i,2,…} ⊆ D_i be its set of primary keys. Finally, let D = {D₁,D₂,…,D_n} and K = {K₁,K₂,…,K_n}...

In recent years a great deal of work has been devoted to the design of interactive database query systems suitable for 'end users'. By contrast, there appears to be little comparable work on interactive facilities for database modification. This is ...

A characterization of an end user and a discussion of an end-user facility are presented. A language for aiding the data-base administrator in designing forms for user's of an end-user facility is described in a tutorial manner. The paper concludes with ...

The purpose of this paper is to analyze the problem of mapping between different levels of a data base.A data Base is viewed as an Abstract Object upon which it is possible to operate with a given set of operations, the result of which depends both on ...

We investigate the inference rules that can be applied to functional and multivalued dependencies that exist in a database relation. Three types of rules are discussed. First, we list the well known rules for functional dependencies. Then we investigate ...

A method for designing a conceptual schema (information model) for a data base is presented. The basic notion is that a conceptual schema is designed by collecting and integrating 'local' user information requirements and analysis of information ...

This research studies the effects of 1) association changes in database semantics, 2) file composition and decomposition, and 3) the conversion of one DBMS to another to the application programs. A methodology of application program analysis and ...

The Access Path Specification Language (APSL) is a high-level essentially nonprocedural language for specifying restructuring transformations of network databases. It does so in terms of application-oriented concepts such as access strategies and ...

A class of external schemas derivable from a tree structured main schema is identified. It is shown that the properties of this class of schemas permit the construction of a processing interface such that predicates defined on an external schema can be ...

A simulation model of concurrent updates in a database system is presented. This model is used, to answer the following questions: How frequent are deadlocks in certain environments? What about concurrency and wait-time of user processes as a function ...

Many data base systems guarantee some form of integrity control upon multiple concurrent updates by some form of locking. Some "granule" of the data base is chosen as the unit which is individually locked, and a lock management algorithm is used to ...

A new algorithm is presented for avoiding system deadlocks. Because its performance has little dependence on the number of lockable resources, it is particularly well suited to use in data base systems which may have millions of individually lockable ...

User performance as well as system related considerations should be part of the DBMS selection process. However, appropriate procedures and measures for determining user performance characteristics of a DBMS are lacking. This paper describes a ...

A top-down approach is proposed for cost analysis for database and information system design. General principles are given which allow the analyst either to estimate rapidly the costs of a wide variety of alternatives or to investigate fewer ...

Performance modelling of data base systems requires taking into consideration the complex interactions between the different physical design parameters and the system workload parameters. In order to facilitate a data base designer in evaluating various ...

Many database maintenance operations are performed periodically in batches, even in real-time systems. The purpose of this paper is to present a general model for determining the optimal frequency of these batch operations. Specifically, optimal backup, ...

This paper describes mechanisms that provide the user of a filing system the dynamic facility for defining a scope within which backing out can be done on request.Check points (defining the beginning of a new scope) can dynamically be established and ...

Predicates are used extensively in modern data base systems, for purposes ranging from user specification of associative accesses to data, to user-invisible system control functions such as concurrency control and data distribution. Collections of ...

We study a number of protection schemes with respect to their effectiveness in providing security for statistical data bases, their feasibility and their ease of implementation. A new method is proposed, and two implementations presented. One ...