In commercial network database management systems, set-valued fields and aggregate functions are commonly supported. However, the relational database model, as defined by Codd, does not include set-valued attributes or aggregate functions. Recently, Klug extended the relational model by incorporating aggregate functions and by defining relational algebra and calculus languages. In this paper, relational algebra and relational calculus database query languages (as defined by Klug) are extended to manipulate set-valued attributes and to utilize aggregate functions. The expressive power of the extended languages is shown to be equivalent. We extend the relational algebra with three new operators, namely, pack, unpack, and aggregation-by-template.The extended languages form a theoretical framework for statistical database query languages. l 567 nonrelational DBMSs suggest that the relational model should be extended with set-valued attributes.Databases mainly used for summary statistics gathering and statistical analysis are called statistical databases (SDB) [13, 261. In SDB applications, set-valued fields and powerful statistical query formulation capabilities are necessary to model the data and to respond to statistical queries [17]. SDBs usually contain aggregated data (e.g., AVERAGE of SALARY) qualified by set-valued attributes (e.g., JOB-GROUPS, AGE-GROUPS). Moreover, queries requesting aggregates almost always are specified over set-valued attributes [17]. In order to use the relational model for SDB applications, in this paper we extend the relational model and the associated relational algebra and relational calculus languages with set-valued attributes and aggregate functions and show that the extended languages have the same query formulation capabilities (i.e., equivalent in expressive power).The algebra and calculus languages defined in this paper form a theoretical basis for "user-friendly" statistical query languages. In [18, 221, we extend the relational model with the summary table object that is composed of set-valued relations and modify the algebra defined in this paper with operators to manipulate summary tables in a unified manner. In [ 191, we define the Summary-Table-by-Example query language that is related to the relational calculus defined here and that manipulates set-valued relations and summary tables. Relations having relations as tuple components are called non-first-normalform (NlNF) relations. Several research results about extending the relational model with NlNF relations have recently been reported. These include Jaesche and Schek [9], who give an algebra for NlNF relations in which attribute domains are limited to power sets of simple-valued (atomic) domains; Orman [14, 151, who defines partitioned relations and nested set languages; Fischer and Thomas [5], who give an algebra for NlNF relations; Abiteboul and Bidoit [ 11, who define NlNF relations to represent hierarchically organized data; and Ozsoyoglu and Yuan [22], who propose a normal form for NlNF relations.In this paper, ...

Table-by-Example (STBE) is a graphical language suitable for statistical database applications. STBE queries have a hierarchical subquery structure and manipulate summary tables and relations with set-valued attributes.The hierarchical arrangement of STBE queries naturally implies a tuple-by-tuple subquery evaluation strategy (similar to the nested loops join implementation technique) which may not be the best query processing strategy. In this paper we discuss the query processing techniques used in STBE. We first convert an STBE query into an "extended" relational algebra (ERA) expression. Two transformations are introduced to remove the hierarchical arrangement of subqueries so that query optimization is possible. To solve the "empty partition" problem of aggregate function evaluation, directional join (one-sided outer-join) is utilized. We give the algebraic properties of the ERA operators to obtain an "improved" ERA expression. Finally we briefly discuss the generation of alternative implementations of a given ERA expression. STBE is implemented in a prototype statistical database management system. We discuss the STBE-related features of the implemented system.

Purpose This paper aims to focus on the role of information and communication technologies (ICTs) in preparation for and management of human and/or nature induced disasters. Design/methodology/approach Drawing from the phenomenal growth of ICTs, initiatives aimed at disaster management, stakeholder theory, prior research and the successful development and implementation of 9-1-1 (emergency telephone service of the USA), this paper explores ICTs in the context of human and/or nature induced disasters. Findings This paper discusses a new ICT for mitigating disaster management, scans, using stakeholder theory, relevant initiatives and prior research to identify the stakeholders relevant for successful preparation for and management of disasters, and draws from the 9-1-1 example to discuss how ICTs can be successfully developed and adopted. Research limitations/implications There are opportunities for researchers to develop ICTs that can make countries, developing and developed, more efficient and effective in their preparation for and management of nature and human induced disasters. In addition, researchers can investigate the role of stakeholders in facilitating the adoption of new ICTs developed for disaster management. Researchers could also help public policy in designing the most efficient and effective programs for the adoption of new ICTs. Practical/implications As an example of new ICTs that can potentially mitigate the effect of disasters, this paper discusses the E711 text-message mobile phone service (named “I am OK”) and provides a description of how this protocol operates and can be implemented. There are tremendous opportunities to develop new ICTs in the context of disaster management. Social/implications This paper argues that ICTs such as E711 can have a major impact on all countries in general and poor and developing nations in particular. Specifically, in the bottom of the pyramid (BOP) markets, developing ICTs for BOP market in the context of managing human and nature induced disasters and ensuring the diffusion of such ICT innovations is both critical and challenging. Originality/value This paper discusses the role and importance of ICTs in disaster management, identifies relevant stakeholders, discusses how ICTs can be diffused and implemented and calls on and hopes to provide an impetus to research on ICTs that can aid in the preparation for and the management of disasters.

The performance of several Fourth Generation Language (4GL) tools is analyzed empirically and compared with equivalent programs written in the third generation COBOL programming language. A set of performance benchmarks consisting of thirteen separate functions is presented which encompasses the areas of simulating the operators of the relational algebra, accessing records in the database, and updating the database. This serves as a baseline for comparing the various 4GL systems.

Students in a typical database course are introduced to theoretical design from a functional dependency standpoint. Functional dependencies are rules of the form X→Y, where X and Y are attributes of a relation r(R). Those rules express the potential one-to-one, and many-to-one relationships among the atributes of R. Unfortunately finding the non-trivial rules X→Y from an existing arbitrary relation is a hard problem. We present an extension of the SQL-based algorithm of Bell and Brockhausen [1] to explore a relation and find its exact and approximate functional dependencies. We use the g3 measure of Kivinen and Mannila to express the degree of approximation of a dependency. This application could be used either as an example or a project in an advanced database course.