1. Systems Analysis and Design
Alan Dennis, Barbara Wixom, and David Tegarden
John Wiley & Sons, Inc.
Slides by Fred Niederman
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2. 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.
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PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design
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3. Object Persistence Design
Chapter 13
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4. 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.
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5. OBJECT PERSISTENCE FORMATS
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6. 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
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7. Other files Master files Transaction files Audit History Look-up
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8. Customer Order File Figure 13-1 Goes Here
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9. 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
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10. 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
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11. Relational Database Example
Figure 13-3 Goes Here
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12. 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
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13. Selecting an Object Persistence Format
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14. 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?
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15. MAPPING PROBLEM DOMAIN OBJECTS TO OBJECT PERSISTENCE FORMATS
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16. 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
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17. Appointment System Problem Domain and Data Management Layers
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18. Factoring Out Multiple Inheritance Effect
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19. Mapping Problem Domain Objects to ORDBMS Schema -- Rules
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20. Mapping Problem Domain Objects to ORDBMS Schema -- Example
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21. 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
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22. Mapping Problem Domain Objects to RDBMS Schema -- Rules
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23. OPTIMIZING RDBMS-BASED OBJECT STORAGE
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24. Dimensions of Data Storage Optimization
Storage efficiency (minimizing storage space)
Speed of access (minimizing time to retrieve desired information)
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25. 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
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26. The Steps of Normalization
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27. First Normal Form (1NF)
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28. Second Normal Form (2NF)
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29. Third Normal Form (3NF)
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30. Optimizing Access Speed
Denormalization
Clustering
Intra-file
Inter-file
Indexing
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31. Payment Type Index
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32. 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
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33. 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%)
Total Record Size 63.7
Initial Table Size 50,000
Initial Table Volume 3,185,000
Growth/Month 1,000
Table
3 years ,478,200
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34. CD Selections
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35. CD Selections
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36. 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.
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37. Expanding the Domain
The Object Data Management Group is working on standardization of the OO database features. Check them out at:
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