Transcript Concepts
Chapter 9 Database Development and Management Introduction to Information Systems Judith C. Simon Slide 9-1 "Copyright © 2001 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein." Slide 9-2 Chapter 9 Major Topics General concepts File organization File access Data models Distributed databases Data warehouses and data mining Knowledge management Slide 9-3 General Concepts Metadata: data about data, such as descriptions and relationships Database: designed to be shared by many people, although the on-screen data and reports may be entirely different for each individual need Entity: each person, place, or thing that is a basis for maintaining data Attribute: individual characteristics about an entity Slide 9-4 File Organization Refers to the way data is stored, i.e., the relationship between a record and its location in a file Address: actual storage location for a record; two types: physical, e.g., cylinder, track and sector used on a disk relative, e.g., record’s position in a file in relation to the beginning of the file; can be used to create a linked list (“pointers”), with each record pointing to the next related record by including its relative address Slide 9-5 File Organization, continued Types of file organization include: Sequential: records stored in a specific order, such as alphabetically, by date, by order number, etc. Indexed sequential: records divided into groups and then arranged sequentially within each group Random ( or “direct”): records stored in any order, with physical location not a concern for location records later Slide 9-6 File Access Concerned with retrieving of files; two options are: Direct (or “random”): requires that one or more fields be used as a “key,” or unique identifier for a record; example: social security number or customer account number, where no two records would have the same number Sequential: files are presented in order from the first or current record to the last in the designated order Slide 9-7 Data Models Refers to designing a database by using related models, starting with a high-level model of some activity, followed by more detailed models, eventually leading to a model identifying details of implementation Conceptual data model: depicts needs from system users’ viewpoints Logical data model: based on conceptual model and includes description of items that need to work together and other related details; often used for communications between developers and users Slide 9-8 Examples of Logical Data Models Hierarchical: top-down (“tree”) structure; main element is at the top, branching down from there; efficient but somewhat inflexible structure for data flow (hierarchical is a one-to-many relationship) Network: has multiple paths for data flow; more complicated to design and manage but reduces unnecessary redundancy (network is a many-tomany relationship) Slide 9-9 Examples of Logical Data Models, continued Relational: relations are shown as two-dimensional tables, with attributes used as columns (fields); linking to another table can occur by having one column of data that is the same in both; most widely used model Object-oriented: reusable system that includes class: person, place, or thing of interest object: instance of a class, containing related data and methods inheritance: new classes can use characteristics of existing classes Slide 9-10 Database Management Systems Refers to a complex set of programs for managing databases Management tasks include controlling access to data coordinating the shared use of data maintaining quality or integrity of data managing input/output operations to ensure that they are as efficient as possible monitoring system performance Slide 9-11 Distributed Databases Uses multiple desktop and other computers to spread the databases over different geographic areas in a network General designs include placing parts of a database in the locations where they are most needed copying (replicating) the entire database at one or more separate locations Entire system will not be shut down from a single power failure, but development and management are more complex Slide 9-12 Data Warehouse Typically uses a centralized data storage system Used for long-range decisions rather than realtime or online decisions Contains recent as well as historical data but does not contain up-to-the-minute data that is constantly changing Contains integrated data from multiple business activities, typically arranged by subject Houses both detailed and summary data Slide 9-13 Data Mining Involves accessing a data warehouse to examine data, often to locate patterns and relationships among items that might not otherwise be noticed, as well as other influences in a set of data Often involves neural network techniques that can adjust as new examples are encountered, combined with decision support tools Widely used for marketing activities, sometimes to predict customer behaviors Slide 9-14 Knowledge Management Refers to systems that include storage of knowledge of various employees that can then be shared with others (their knowledge includes such things as methods they have used for successful handling of situations and other procedures that are not otherwise found in programs or databases) Often used to assist in business decisions or to improve customer service Slide 9-15 Slide 9-16