Systems Analysis and Design Alan Dennis, Barbara Wixom, and David Tegarden John Wiley & Sons, Inc. Slides by Fred Niederman PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

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 redistribution 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. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Object Persistence Design Chapter 13 PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Key Definitions Object persistence involves the selection of a storage format and optimization for performance. Four basic formats used for object persistence are: files, OO databases, object-relational, and relational databases. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

OBJECT PERSISTENCE FORMATS PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Files Sequential Access Data stored in order based on a particular attribute Typically efficient for reports using all or most of the file’s data Random Access Data stored in unordered fashion Typically efficient for finding individual records PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Other files Master files Transaction files Audit History Look-up PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Customer Order File Figure 13-1 Goes Here PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Relational Databases Primary key Foreign key Referential integrity Structured Query Language (SQL) Tables Joining tables Objects must be converted so they can be stored in a table PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Object-Relational Databases Relational databases extended to handle the storage of objects Use of user-defined data types Extended SQL Inheritance tends to be language dependent PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Relational Database Example Figure 13-3 Goes Here PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Object-Oriented Databases Two approaches Adding persistence extensions to OO languages Separate database management systems Extents Object ID assigned Some inheritance Repeating groups or multivalued attributes Mainly support multimedia applications Sharp learning curve PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Selecting an Object Persistence Format PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Your Turn A major university graduates about 10,000 students a year and the development office wants to build a web-based system to solicit and track donations. What are the pros and cons of each data storage format for this sort of application? PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

MAPPING PROBLEM DOMAIN OBJECTS TO OBJECT PERSISTENCE FORMATS PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Initial Points to Consider Adding primary and foreign keys Unless they add too much overhead Data management functionality only in classes at data management layer May add overhead, but aids in portability and reuse PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Appointment System Problem Domain and Data Management Layers PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Factoring Out Multiple Inheritance Effect PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Mapping Problem Domain Objects to ORDBMS Schema -- Rules PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Mapping Problem Domain Objects to ORDBMS Schema -- Example PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Maintain a Clean Problem Domain Layer Modifying the problem domain layer can create problems between the system architecture and human computer interface layer The development and production costs of OODBMS may offset the production cost of having the data management layer implemented in ORDBMS PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Mapping Problem Domain Objects to RDBMS Schema -- Rules PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

OPTIMIZING RDBMS-BASED OBJECT STORAGE PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Dimensions of Data Storage Optimization Storage efficiency (minimizing storage space) Speed of access (minimizing time to retrieve desired information) PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Optimizing Storage Efficiency Reduce redundant data Limit null values Multiple possible interpretations can lead to mistakes A well-formed logical data model does not contain redundancy or many null values PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

The Steps of Normalization PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

First Normal Form (1NF) PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Second Normal Form (2NF) PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Third Normal Form (3NF) PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Optimizing Access Speed Denormalization Clustering Intra-file Inter-file Indexing PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Payment Type Index PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Guidelines for Creating Indexes Use indexes sparingly for transaction systems Use many indexes to increase response times in decision support systems For each table Create a unique index based on the primary key Create an index based on the foreign key Create an index for fields used frequently for grouping, sorting, or criteria PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Estimating Data Storage Size Field Average Size (Characters) Order number 8 Date 7 Cust ID 4 Last name 13 First name 9 State 2 Amount 4 Tax rate 2 Record Size 49 Overhead (30%) 14.7 Total Record Size 63.7 Initial Table Size 50,000 Initial Table Volume 3,185,000 Growth/Month 1,000 Table volume @ 3 years 5,478,200 PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

CD Selections PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

CD Selections PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Summary There are four basic types of object persistence formats: files (sequential and random access), object-oriented databases, object-relational databases, and relational databases. Tradeoffs between the formats make it necessary to consider which to apply in each environment Once the format has been selected, data storage needs to be optimized for efficiency and speed of access. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Expanding the Domain The Object Data Management Group is working on standardization of the OO database features. Check them out at: http://www.odmg.org PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.