system architecture for approximate query processing

Decision making is an activity that addresses the problem of extracting knowledge and information from data stored in data warehouses, in order to improve the business processes of information systems. Usually, decision making is based on On-Line Analytical Processing, data mining, or approximate query processing. In the last case, answers to analytical queries are provided in a fast manner, although affected with a small percentage of error. In the paper, we present the architecture of an approximate query answering system. Then, we illustrate our ADAP (Analytical Data Profile) system, which is based on an engine able to provide fast responses to the main statistical functions by using orthogonal polynomials series to approximate the data distribution of multi­dimensional relations. Moreover, several experimental results to measure the approximation error are shown and the response-time to analytical queries is reported.</p

A METHODOLOGY FOR REVERSE ENGINEERING HIERARCHICAL DATABASES

This paper describes the steps of a reverse engineering process for translating a hierarchical data schema into a conceptual description in the extended entity-relationship model. The methodology presented is composed of well-defined tasks which, due to the good level of automation, forecast the possibility of a profitable use of CASE tools. However, the final production of a semantically richer conceptual schema requires the involvement of the designer, whose experience could be implemented with artificial intelligent techniques. The forward process is also analysed to determine all useful decisions which could be applied in the reverse methodology. In addition, an example is presented which illustrates the real applicability of the proposed approach

ARCHO: A computer based learning system for teaching computer architectures

The paper describes an educational system aimed at providing a course of computer architecture for graduate students. The system, called ARCHO, is composed by teacher oriented modules (to build lectures, exercises, computer architectures) and students oriented modules (to navigate the hypertext lectures, to resolve exercises and to compile programs on the computer processor simulator). ARCHO provides and integrates two different systems: ARCAL to support the study of theoretical concepts and to verify lectures and APE to support the laboratory activity by the building and using a computer architecture simulator

An Object Oriented Tool to Simulate Multi-Level Computer Architectures

We describe a simulator that is a useful supporting tool in all activities involving computer architecture teaching. The system, developed using an object-oriented approach, integrates in a single tool different architecture models, such as CISC and RISC architecture types, and different computer levels, such as microprogramming and instruction set levels. The system allows the user to define the computer architecture at the instruction set level and then to switch automatically to the lower level of the corresponding microarchitecture. The simulation process consists of a loop, in which two strictly correlated phases are executed: the definition phase, in which the user defines the architecture through a choice of hardware components, and a test phase, in which the user tests the designed architecture in order to verify the result of the design activity of the previous phase. Once the processor design has been completed through this simulation process, the tool allows the user to save and use a stand-alone simulator of the target computer architecture. The definition and simulation activities of the computer architecture are supported by a graphical user interface for an effective, easy-to-use teaching environment

A rapid prototyping environment for designing and simulating multilevel computer architectures

This paper describes a software environment that allows the rapid development and simulation of computer architectures. The system, called the Architecture Prototyping Environment (APE), is based on an object-oriented approach for hardware component description. This approach allows the formation of a class definition that does not require the writing of special-purpose simulators. In this way, computer architecture hardware components are effectively and conveniently expressed as a class library, representing basic elements of the processor. APE allows the user to define the computer architecture at the instruction set level and then to switch automatically to the lower level of the corresponding microarchitecture. APE supports the design of a computer architecture (definition phase), which is used as a starting point for the next phase for evaluating prototype behavior (test phase). APE accepts modifications of the architecture design and repeats the simulation process until architectural features match user requirements

PROLOG SIMULATION OF COMPUTER ARCHITECTURE IN LABORATORY ACTIVITIES

Implementation of a computer architecture simulator prototype written in Turbo Prolog, which is suitable for educational purposes, is described. Besides adapting to teaching needs for conventional use, the simulator design incorporates features for an easy alteration of computer architectural structures appropriate to the trainee's learning level. Thus, this simulator is not limited to a particular architecture but permits the student to vary dynamically the architectural characteristics of the computer under study in order to verify the consequences of his decisions and to experiment with families of computers and alternatives of design