A Study to Determine the Sources of Friction Between Parents and the Yakima Public Schools

The purposes of this study are threefold: 1. To study recorded individual complaints directed at a Class A public school system during the period of one full year. 2. To identify the source of these misunderstandings and possibly the reasons for their occurrence. 3. To suggest some common methods of dealing with parents and the public at large in an effort to eliminate the criticisms

OBJECTS IN TIME

Two recent lines of database research, proceeding independently, have been concerned with providing a richer, more intuitive view of information at the user level. Historical database research has focused on ways to provide users with a view of information anchored and evolving in the temporal dimension. Object-oriented database research focuses on encapsulating both the structure and the behavior of the objects that users intend to model. In this paper we explore how these two lines of research might be brought together, providing to the user the representation and management of objects in time.Information Systems Working Papers Serie

THE HISTORICAL RELATIONAL DATA MODEL (HRDM) AND ALGEBRA BASED ON LIFESPANS

Critical to the design of an historical database model is the representation of the âexistenceâ of objects across the temporal dimension -- for example, the "birth," "death," or "rebirth" of an individual, or the establishment or dis-establishment of a relationship. The notion of the "lifespan" of a database object is proposed as a simple framework for expressing these concepts. An object's lifespan is simply those periods of time during which the database models the properties of that object. In this paper we propose the historical relational data model (HRDM) and algebra that is based upon lifespans and that views the values of all attributes as functions from time points to simple domains. The model that we obtain is a consistent extension of the relational data model, and provides a simple mechanism for providing both time-varying data and time-varying schemes.Information Systems Working Papers Serie

ON CONSISTENT EXTENSIONS TO THE RELATIONAL DATABASE MODEL

Information Systems Working Papers Serie

ON COMPLETENESS OF HISTORICAL RELATIONAL DATA MODELS

Several proposals for extending the relational data model to incorporate the temporal dimension of data have appeared in the past several years. These proposals have differed considerably in the way that the temporal dimension has been incorporated both into the structure of the extended relations that are defined as part of these extended model, and into the operations of the extended relational algebra or calculus component of the models. Because of these differences it has been difficult to compare the proposed models and to make judgements as to which of them is "better" or indeed, the "best." In this paper we propose a notion of historical relational completeness, analogous to Codd's notion of relational completeness, and examine several historical relational proposals in light of this standard.Information Systems Working Papers Serie

ON COMPLETENESS OF HISTORICAL RELATIONAL QUERY LANGUAGES

Numerous proposals for extending the relational data model to incorporate the temporal dimension of data have appeared in the past several years. These proposals have differed considerably in the way that the temporal dimension has been incorporated both into the structure of the extended relations of these temporal models, and consequently into the extended relational algebra or calculus that they define. Because of these differences it has been difficult to compare the proposed models and to make judgments as to which of them might in some sense be equivalent or even better. In this paper we define the notions of temporally grouped and temporally ungrouped historical data models and propose two notions of historical relational completeness, analogous to Codd's notion of relational completeness, one for each type of model. We show that the temporally ungrouped models are less powerful than the grouped models, but demonstrate a technique for extending the ungrouped models with a grouping mechanism to capture the additional semantic power of temporal grouping. For the ungrouped models we define three different languages, a temporal logic, a logic with explicit reference to time, and a temporal algebra, and show that under certain assumptions all three are equivalent in power. For the grouped models we define a many-sorted logic with variables over ordinary values, historical values, and times. Finally, we demonstrate the equivalence of this grouped calculus and the ungrouped calculus extended with the proposed grouping mechanism. We believe the classification of historical data models into grouped and ungrouped provides a useful framework for the comparison of models in the literature, and furthermore the exposition of equivalent languages for each type provides reasonable standards for common, and minimal, notions of historical relational completeness.Information Systems Working Papers Serie

On Completeness of Historical Relational Query Languages

Numerous proposals for extending the relational data model to incorporate the temporal dimension of data have appeared in the past several years. These proposals have differed considerably in the way that the temporal dimension has been incorporated both into the structure of the extended relations of these temporal models, and consequently into the extended relational algebra or calculus that they define. Because of these differences it has been difficult to compare the proposed models and to make judgments as to which of them might in some sense be equivalent or even better. In this paper we define the notions of temporally grouped and temporally ungrouped historical data models and propose two notions of historical reIationa1 completeness, analogous to Codd's notion of relational completeness, one for each type of model. We show that the temporally ungrouped models are less expressive than the grouped models, but demonstrate a technique for extending the ungrouped models with a grouping mechanism to capture the additional semantic power of temporal grouping. For the ungrouped models we define three different languages, a temporal logic, a logic with explicit reference to time, and a temporal algebra, and show that under certain assumptions all three are equivalent in power. For the grouped models we define a many-sorted logic with variables over ordinary values, historical values, and times. Finally, we demonstrate the equivalence of this grouped calculus and the ungrouped calculus extended with a grouping mechanism. We believe the classification of historical data models into grouped and ungrouped provides a useful framework for the comparison of models in the literature, and furthermore the exposition of equivalent languages for each type provides reasonable standards for common, and minimal, notions of historical relational completeness.Information Systems Working Papers Serie

On Data Representation and Use In A Temporal Relational DBMS

Numerous proposals for extending the relational data model to incorporate the temporal dimension of data have appeared over the past decade. It has long been known that these proposals have adopted one of two basic approaches to the incorporation of time into the extended relational model. Recent work formally contrasted the expressive power of these two approaches, termed temporally ungrouped and temporally grouped, and demonstrated that the temporally grouped models are more expressive. IN the temporally ungrouped models, the temporal dimension is added through the addition of some number of distinguished attributes to the schema of each relation, and each tuple is "stamped" with temporal values for these attributes. By contrast, in temporally grouped models the temporal dimension is added to the types of values that serve as the domain of each ordinary attribute, and the application's schema is left intact. The recent appearance of TSQL2, a temporal extension to the SQL-92 standard based upon the temporally ungrouped paradigm, means that it is likely that commercial DBMS's will be extended to support time in this weaker way. Thus the distinction between these two approaches - and its impact on the day-to-day user of a DBMS - is of increasing relevance to the database practitioner and the database user community. In this paper we address this issue from the practical perspective of such a user. Through a series of example queries and updates, we illustrate the differences between these two approaches and demonstrate that the temporally grouped approach more adequately captures the semantics of historical data.Information Systems Working Papers Serie

An Exploratory Analysis of Developmental Sequences in Interorganizational Coalitions Involved in Community Planning

This study is one of four exploratory studies concerned with coalitions of organizations that are formed to plan and develop social welfare programs within the local community. Although each study was conducted independently, taken together, their major purpose was to develop some insights and knowledge into the behavior of organizations and the ways in which they interact as they work together to develop community programs. They are then, exploratory studies of interorganizational behavior