1. PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 1 Systems Analysis and Design Alan Dennis, Barbara Wixom, and David Tegarden John Wiley & Sons, Inc. Slides by Fred Niederman

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

3. PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 3 Object Persistence Design Chapter 13

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

5. PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 5 OBJECT PERSISTENCE FORMATS

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

7. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 7 Types of Files Master files – store core data Look-up files – reference information tat is used during validation processing (valid codes, etc) Transaction files – temporary files of data that will update a master file Audit files – trace changes made to files History files – contain archived data

8. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 8 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

9. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 9 Customer Order File Figure 13-1 Goes Here

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

11. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 11 Relational Database Example Figure 13-3 Goes Here

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

13. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 13 Selecting an Object Persistence Format

14. PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 14 MAPPING PROBLEM DOMAIN OBJECTS TO OBJECT PERSISTENCE FORMATS

15. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 15 The Process of Analysis Identify a problem Analyze the problem The conceptualization is of the problem domain Analysis becomes models Models are iterated into the system design

16. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 16 Process of Design Design strives to map the problem domain to the technological solution In UML, classes build the foundation

17. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 17 Example Class Diagram

19. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 19

20. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 20 Problem Domain to Design How do you move from the problem domain to the design of the technology? Recognize that other classes are needed to facilitate implementation of the design

21. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 21 Layers of Classes FOUNDATIONtypically available with development language SYSTEM ARCHITECTUREhow the software will execute HUMAN-COMPUTER INTERACTIONUser interface (web pages for example) DATA MANAGEMENTdeals with persistence how objects will be stored and retrieved PROBLEM DOMAINenvironment view

22. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 22 Mapping for Persistence Focus is on identifying what must be persisted (stored, etc). Mapping those classes from the problem domain to the data management domain

23. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 23 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

24. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 24 Appointment System Problem Domain and Data Management Layers

25. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 25 Factoring Out Multiple Inheritance Effect Add attribute of Object Id for subclass Copy attributes and methods of ‘extra’ subclass to all data management subclasses

26. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 26 Mapping Problem Domain Objects to ORDBMS Schema Problem domain classes are mapped to data management classes and then to database tables

27. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 27 Mapping Problem Domain Objects to ORDBMS Schema -- Example

28. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 28 Mapping to OORDMS Handling attributes Map single-valued attributes to Columns in the table Set of access methods in the data management class

29. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 29 Mapping to OORDMS Handling Methods Methods (and derived attributes) can be mapped to stored procedures or problem modules

30. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 30 Mapping to OORDMS Handling Relationships Map simple relationships and aggregation to a column that stores an Object ID (ie similar to a foreign key)

31. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 31 Mapping to OORDMS Other major steps Multi-valued attributes are mapped to columns that contain a set of values Repeating groups of attributes can be used to create a new table Map many-to-many using a combination of the 2 steps above Deal with generalization and inheritance

32. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 32 Mapping Problem Domain Objects to ORDBMS Schema -- Rules

33. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 33 Mapping Problem Domain Objects to RDBMS Schema Problem domain classes are mapped to data management classes and then to database tables (same as OORDBMS)

34. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 34 Mapping Problem Domain Objects to RDBMS Schema - Map single-valued attributes to Columns in the table Set of access methods in the data management class Methods (and derived attributes) can be mapped to stored procedures or problem modules

35. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 35 Mapping to RDMS Handling Relationships Map simple relationships and aggregation to a column that stores a foreign key for the related tables

36. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 36 Mapping to RDMS Other major steps Multi-valued attributes are mapped to new tables Repeating groups of attributes can be used to create a new table and often a new problem domain class Map many-to-many to a new table that relates the 2 original tables Deal with generalization and inheritance

37. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 37 Mapping Problem Domain Objects to RDBMS Schema -- Rules

38. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 38 Which to use? Generic customer information? Pictures, video segments, etc? Temporary data? Data needed to process a web page that you do not want to store on the server?

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

40. PowerPoint Presentation for Dennis, Wixom & Tegarden Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 40 OPTIMIZING RDBMS-BASED OBJECT STORAGE

41. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 41 Dimensions of Data Storage Optimization Storage efficiency (minimizing storage space) Speed of access (minimizing time to retrieve desired information)

42. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 42 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

43. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 43 The Steps of Normalization

44. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 44 Optimizing Access Speed Denormalization Clustering Intra-file Inter-file Indexing

45. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 45 Payment Type Index

46. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 46 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

47. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 47 Steps for Estimating Size of a DB 1. Calculate raw data needs 2. Calculate overhead as percentage of each record 1. Past experience, vendor recommendations, etc. 3. Record number of records to be initially loaded and expected monthly growth

48. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 48 Estimating Data Storage Size FieldAverage Size (Characters) Order number 8 Date 7 Cust ID 4 Last name13 First name 9 State 2 Amount 4 Tax rate 2 Record Size49 Overhead (30%)14.7 Total Record Size63.7 Initial Table Size50,000 Initial Table Volume 3,185,000 Growth/Month 1,000 Table volume @ 3 years 5,478,200

49. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 49 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