12 si(systems analysis and design )
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This chapter discusses database design and management. It describes relational and object-oriented database models. For relational databases, entities are represented as tables related by primary and foreign keys. Object databases represent data as objects with attributes and relationships. Hybrid systems store objects in relational databases. The chapter also covers distributed databases which partition data across multiple physical locations for performance and availability.
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12 si(systems analysis and design )
- 1. Chapter 12: Designing Databases Systems Analysis and Design in a Changing World, Fourth Edition 12
- 2. Learning Objectives Describe the differences and similarities between relational and object-oriented database management systems Design a relational database schema based on an entity-relationship diagram Design an object database schema based on a class diagram Systems Analysis and Design in a Changing World, 4th Edition
- 3. Learning Objectives ( continued ) Design a relational schema to implement a hybrid object-relational database Describe the different architectural models for distributed databases Systems Analysis and Design in a Changing World, 4th Edition
- 4. Overview This chapter describes design of relational and OO data models Developers transform conceptual data models into detailed database models Entity-relationship diagrams (ERDs) for traditional analysis Class diagrams for object-oriented (OO) analysis Detailed database models are implemented with database management system (DBMS) Systems Analysis and Design in a Changing World, 4th Edition
- 5. Databases and Database Management Systems Databases (DB) – integrated collections of stored data that are centrally managed and controlled Database management system (DBMS) – system software that manages and controls access to database Databases described by a schema – description of structure, content, and access controls Systems Analysis and Design in a Changing World, 4th Edition
- 6. Components of a DB and DBMS Systems Analysis and Design in a Changing World, 4th Edition
- 7. Important DBMS Capabilities Simultaneous access by multiple users and applications Access to data without application programs (via a query language) Organizational data management with uniform access and content controls Systems Analysis and Design in a Changing World, 4th Edition
- 8. Database Models Impacted by technology changes since 1960s Model types Hierarchical Network Relational Object-oriented Most current systems use relational or object-oriented data models Systems Analysis and Design in a Changing World, 4th Edition
- 9. Relational Databases Relational database management system (RDBMS) organizes data into tables or relations Tables are two dimensional data structures Tuples – rows or records Fields – columns or attributes Tables have primary key field(s) that can be used to identify unique records Keys relate tables to each other Systems Analysis and Design in a Changing World, 4th Edition
- 10. Partial Display of Relational Database Table (Figure 12-2) Systems Analysis and Design in a Changing World, 4th Edition
- 11. Designing Relational Databases Create table for each entity type Choose or invent primary key for each table Add foreign keys to represent one-to-many relationships Create new tables to represent many-to-many relationships Systems Analysis and Design in a Changing World, 4th Edition
- 12. Designing Relational Databases ( continued ) Define referential integrity constraints Evaluate schema quality and make necessary improvements Choose appropriate data types and value restrictions (if necessary) for each field Systems Analysis and Design in a Changing World, 4th Edition
- 13. Relationship Between Data in Two Tables Systems Analysis and Design in a Changing World, 4th Edition
- 14. RMO Entity-Relationship Diagram (Figure 12-5) Systems Analysis and Design in a Changing World, 4th Edition
- 15. Representing Relationships Relational databases use foreign keys to represent relationships One-to-many relationship Add primary key field of “one” entity type as foreign key in table that represents “many” entity type Many-to-many relationship Use the primary key field(s) of both entity types Use (or create) an associative entity table to represent relationship Systems Analysis and Design in a Changing World, 4th Edition
- 16. Entity Tables with Primary Keys (Figure 12-7) Systems Analysis and Design in a Changing World, 4th Edition
- 17. Represent One-to-Many Relationships by Adding Foreign Keys (in italics) (Figure 12-8) Systems Analysis and Design in a Changing World, 4th Edition
- 18. Enforcing Referential Integrity Consistent relational database state Every foreign key value also exists as a primary key value DBMS enforces referential integrity automatically after schema designer identifies primary and foreign keys Systems Analysis and Design in a Changing World, 4th Edition
- 19. DBMS Referential Integrity Enforcement When rows containing foreign keys are created DBMS ensures that value also exists as a primary key in a related table When row is deleted DBMS ensures no foreign keys in related tables have same value as primary key of deleted row When primary key value is changed DBMS ensures no foreign key values in related tables contain the same value Systems Analysis and Design in a Changing World, 4th Edition
- 20. Evaluating Schema Quality High-quality data model has Uniqueness of table rows and primary keys Ease of implementing future data model changes (flexibility and maintainability) Lack of redundant data (database normalization ) Database design is not objective or quantitatively measured; it is experience and judgment based Systems Analysis and Design in a Changing World, 4th Edition
- 21. Database Normalization Normal forms minimize data redundancy First normal form (1NF) – no repeating fields or groups of fields Functional dependency – one-to-one relationship between the values of two fields 2NF – in 1NF and if each non-key element is functionally dependent on entire primary key 3NF – in 2NF and if no non-key element is functionally dependent on any other non-key element Systems Analysis and Design in a Changing World, 4th Edition
- 22. Decomposition of 1NF Table into 2NF Tables Systems Analysis and Design in a Changing World, 4th Edition IssueDate is determined by CatalogID alone, not by both CatalogID and ProductID
- 23. Conversion of 2NF Table into 3NF Tables Systems Analysis and Design in a Changing World, 4th Edition ZipCode determines the value for State, and ZipCode is not the key to the table
- 24. Object-Oriented Databases Direct extension of OO design and programming paradigm ODBMS stores data as objects Direct support for method storage, inheritance, nested objects, object linking, and programmer-defined data types Object Definition Language (ODL) Standard language for describing structure and content of an object database Systems Analysis and Design in a Changing World, 4th Edition
- 25. Designing Object Databases Determine which classes require persistent storage Define persistent classes Represent relationships among persistent classes Choose appropriate data types and value restrictions (if necessary) for each field Systems Analysis and Design in a Changing World, 4th Edition
- 26. Representing Classes Transient classes Objects exist only during lifetime of program or process Examples: view layer window, pop-up menu Persistent classes Objects not destroyed when program or process ceases execution. State must be remembered. Exist independently of program or process Examples: customer information, employee information Systems Analysis and Design in a Changing World, 4th Edition
- 27. Representing Relationships Object identifiers Used to identify objects uniquely Physical storage address or reference Relate objects of one class to another ODBMS uses attributes containing object identifiers to find objects that are related to other objects Keyword relationship can be used to declare relationships between classes Systems Analysis and Design in a Changing World, 4th Edition
- 28. Representing Relationships ( continued ) Advantages include ODBMS assumes responsibility for determining connection among objects ODBMS assumes responsibility for maintaining referential integrity Type of relationships 1:1, 1:M, M:M (one-to-one, one-to-many, many-to-many) Association class used with M:M Systems Analysis and Design in a Changing World, 4th Edition
- 29. RMO Domain Model Class Diagram (Figure 12-15) Systems Analysis and Design in a Changing World, 4th Edition
- 30. One-to-One Relationship Represented with Attributes Containing Object Identifiers Systems Analysis and Design in a Changing World, 4th Edition
- 31. One-to-Many Relationship Between Customer and Order Classes Systems Analysis and Design in a Changing World, 4th Edition
- 32. One-to-Many Relationship Represented with Attributes Containing Object Identifiers Systems Analysis and Design in a Changing World, 4th Edition
- 33. Many-to-Many Relationship between Employee and Project Classes (Figure 12-19) Systems Analysis and Design in a Changing World, 4th Edition
- 34. Generalization Hierarchy within the RMO Class Diagram (Figure 12-21) Systems Analysis and Design in a Changing World, 4th Edition
- 35. Hybrid Object-Relational Database Design RDBMS ( hybrid DBMS ) used to store object attributes and relationships Design complete relational schema and simultaneously design equivalent set of classes Mismatches between relational data and OO Class methods cannot be directly stored or automatically executed Relationships are restricted compared to ODBMS ODBMS can represent wider range of data types Systems Analysis and Design in a Changing World, 4th Edition
- 36. Classes and Attributes Designers store classes and object attributes in RDBMS by table definition Relational schema can be designed based on class diagram Table is created for each class Fields of each table same as attributes of class Row holds attribute values of single object Key field is chosen for each table Systems Analysis and Design in a Changing World, 4th Edition
- 37. Views of Stored Data Systems Analysis and Design in a Changing World, 4th Edition
- 38. Relationships Relationships are represented with foreign keys Foreign key values serve same purpose as object identifiers in ODBMS 1:M relationship – add primary key field of class on “one” side of the relationship to table representing class on “many” side M:M relationship – create new table that contains primary key fields of related class tables and attributes of the relationship itself Systems Analysis and Design in a Changing World, 4th Edition
- 39. Data Access Classes OO design based on a three-layer architecture Data access classes are implementation bridge between data stored in program objects and data in relational database Methods add, update, find, and delete fields and rows in table or tables that represent the class Methods encapsulate logic needed to copy data values from problem domain class to database and vice versa Systems Analysis and Design in a Changing World, 4th Edition
- 40. Interaction Among a Domain Class, a Data Access Class, and the DBMS (Figure 12-25) Systems Analysis and Design in a Changing World, 4th Edition
- 41. Data Types Storage format and allowable content of program variable, object state variable, or database field or attribute Primitive data types – directly implemented Memory address (pointer), Boolean, integer, and so on Complex data types – user-defined Dates, times, audio streams, video images, URLs Systems Analysis and Design in a Changing World, 4th Edition
- 42. Relational DBMS Data Types Designer must choose appropriate data type for each field in relational database schema Choice for many fields is straightforward Names and addresses use a set of fixed- or variable-length character arrays Inventory quantities can use integers Item prices can use real numbers Complex data types (DATE, LONG, LONGRAW) Systems Analysis and Design in a Changing World, 4th Edition
- 43. Subset of Oracle RDBMS Data Types Systems Analysis and Design in a Changing World, 4th Edition
- 44. Object DBMS Data Types Use set of primitive and complex data types comparable to RDBMS data types Schema designer can create new data types and associated constraints Classes are complex user-defined data types that combine traditional concept of data with processes (methods) to manipulate data Flexibility to define new data types is one reason that OO tools are widely used Systems Analysis and Design in a Changing World, 4th Edition
- 45. Distributed Databases Rare for all organizational data to be stored in a single database in one location Different information systems in an organization are developed at different times Parts of an organization’s data may be owned and managed by different units System performance is improved when data is near primary applications Systems Analysis and Design in a Changing World, 4th Edition
- 46. Single Database Server Architecture (Figure 12-27) Systems Analysis and Design in a Changing World, 4th Edition
- 47. Replicated Database Server Architecture (Figure 12-28) Systems Analysis and Design in a Changing World, 4th Edition
- 48. Partitioning Database Schema into Client Access Subsets Systems Analysis and Design in a Changing World, 4th Edition
- 49. Partitioned Database Server Architecture Systems Analysis and Design in a Changing World, 4th Edition
- 50. Federated Database Server Architecture Systems Analysis and Design in a Changing World, 4th Edition
- 51. RMO Distributed Database Architecture Starting point for design was information about data needs of geographically dispersed users RMO gathered information during analysis phase RMO decided to manage database using Park City data center mainframe RMO is evaluating single-server vs. replicated and partitioned database server architectures Information on network traffic and costs needed Systems Analysis and Design in a Changing World, 4th Edition
- 52. Single-Server Database Server Architecture for RMO Systems Analysis and Design in a Changing World, 4th Edition
- 53. Replicated and Partitioned Database Server Architecture for RMO Systems Analysis and Design in a Changing World, 4th Edition
- 54. Summary Modern information systems store data in database and access and manage data using DBMS Relational DBMS is commonly used Object DBMS is increasing in popularity Key activity of systems design is developing relational or object database schema Relational database is collection of data stored in tables and is developed from entity-relationship diagram Systems Analysis and Design in a Changing World, 4th Edition
- 55. Summary ( continued ) Object database stores data as collection of related objects and is developed from class diagram Objects can also be stored in RDBMS RDBMS cannot store methods RDBMS cannot directly represent inheritance Medium and larger information systems typically use multiple databases or database servers in various geographic locations Systems Analysis and Design in a Changing World, 4th Edition
- 56. Systems Analysis and Design in a Changing World, 4th Edition Thank You Nurdin Al-Azies http://www.azies-site.co.cc [email_address]