1. Information Systems Chapter 2 Organizing Data and Information

2. Data –A necessity for almost any enterprise to carry out its business. Consists of raw facts, and when organized may be transformed into information Database –A collection of data organized to meet users’ needs Database management system (DBMS) –A group of programs that manipulate the database and provide an interface between the database and the user of the database or other application programs

3. DBMS ‘Discussion’ (1) A collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes. The following are examples of database applications: – computerized library systems – automated teller machines – flight reservation systems – computerized parts inventory systems From a technical standpoint, DBMSs can differ widely. The terms

4. DBMS ‘Discussion’ (2) relational, network, flat, and hierarchical all refer to the way a DBMS organizes information internally. The internal organization can affect how quickly and flexibly you can extract information. Requests for information from a database are made in the form of a query, which is a stylized question. For example, the query SELECT ALL WHERE NAME = "SMITH" AND AGE > 35 requests all records in which the NAME field is SMITH and the AGE

5. DBMS ‘Discussion’ (3) field is greater than 35. The set of rules for constructing queries is known as a query language. Different DBMSs support different query languages, although there is a semi-standardized query language called SQL (structured query language). Sophisticated languages for managing database systems are called fourth-generation languages, or 4GLs for short. The information from a database can be presented in a variety of formats. Most DBMSs include a report writer program that enables you to output data in the form of a report. Many DBMSs also include

6. DBMS ‘Discussion’ (4) a graphics component that enables you to output information in the form of graphs and charts.

7. Hierarchy of Data Hierarchy of dataExample Database Files Records Fields Characters (bytes) Personel file Department file Payroll file (Project database) 005-10-6321 Johns Francine 10-7-65 549-77-1001 Buckley Bill 2-17-79 098-40-1370 Fiske Steven 1-5-85 (Personnel file) 098-40-1370 Fiske Steven 1-5-85 598 (Record containing SSN, last name, first name, date of hire) Fiske (Last name field) 1000100 (Letter ‘F’ in ASCII)

8. Terminology Database A collection of integrated and related files File A collection of related records Record A collection of related fields Field A group of characters Character Basic building block of information, represented by a byte

9. Data Entities, Attributes, and Keys Entity A generalized class of people, places, or things (objects) for which data are collected, stored, and maintained E.g., Customer, Employee Attribute A characteristic of an entity; something the entity is identified by E.g., Customer name, Employee name Keys A field or set of fields in a record that is used to identify the record E.g, A field or set of fields that uniquely identifies the record

10. Keys and Attributes Key field Attributes (fields) Entities (records) Employee #Last nameFirst nameHire dateDept. # 005-10-6321JohnsFrancine10-7-65257 549-77-1001BuckleyBill2-17-79650 098-40-1370FiskeSteven1-5-85598

11. The Traditional Approach The traditional approach… – Separate files are created and stored for each application program Payroll Payroll programs Reports DataFiles Application programs Users Invoicing Invoicing programs Reports Inventory control Inventory control programs Reports Management inquiries Management inquiries programs Reports

12. Drawbacks Data redundancy –Duplication of data in separate files Lack of data integrity –The degree to which the data in any one file is accurate Program-data dependence –A situation in which program and data organized for one application are incompatible with programs and data organized differently for another application

13. Database Approach The database approach… –A pool of related data is shared by multiple application programs –Rather than having separate data files, each application uses a collection of data that is either joined or related in the database

14. Payroll data Inventory data Invoicing Data Other data Database management system Payroll program Inventory program Invoicing program Other programs Reports DatabaseInterfaceApplications programsUsers

15. Advantages – Improved strategic use of corporate data – Reduced data redundancy – Improved data integrity – Easier modification and updating – Data and program independence – Better access to data and information – Standardization of data access – A framework for program development – Better overall protection of the data – Shared data and information resources

16. Disadvantages –Relatively high cost of purchasing and operating a DBMS in a mainframe operating environment – Increased cost of specialized staff – Increased vulnerability

17. Data Modeling and Database Models (1) Planned data redundancy –A way of organizing data in which the logical database design is altered so that certain data entities are combined –Summary totals are carried in the data records rather than calculated from elemental data –Some data attributes are repeated in more than one data entity to improve database performance

18. Data Modeling and Database Models (2) Data model –A map or diagram of entities and their relationships Enterprise data modeling –Data modeling done at the level of the entire organization Entity-relationship (ER) diagrams –A data model that uses basic graphical symbols to show the organization of and relationships between data

19. Example: Entity Relationship (ER) Diagram for a Customer Ordering Database CUSTOMER IdNumber FisrtName LastName PRODUCT IdProd Name Colour Order 1,n relationship entities attributes

20. Hierarchical Database Model Hierarchical database model –A data model in which data are organized in a top-down, or inverted tree structure Department C Employee 1 Employee 2 Employee 3 Employee 4 Employee 5 Employee 6 Department B Project 1 Department A

21. Network Data Model Network data model An expansion of the hierarchical database model with an owner- member relationship in which a member may have many owners Project 1 Project 2 Department ADepartment BDepartment C

22. Relational Data Model Relational data model –All data elements are placed in two-dimensional tables, called relations, that are the logical equivalent of files Project NumberDescriptionDept. Number 155Payroll257 498Widgets632 226Sales manager598 Dept. NumberDept. NameManager SSN 257Accounting421-55-99993 632Manufacturing765-00-3192 598Marketing098-40-1370 SSNLast NameFirst NameHire DateDept. Number 005-10-6321JohnsFrancine10-7-65257 549-77-1001BuckleyBill2-17-79650 098-40-1370FiskeSteven1-5-85598 Data Table 1: Project Table Data Table 2: Department Table Data Table 3: Manager Table

23. Relational Database Terminology Selecting –Data manipulation that eliminates rows according to certain criteria Projecting –Data manipulation that eliminates columns in a table Joining –Data manipulation that combines two or more tables Linked –Relating tables in a relational database together

24. Linking Data Tables to Answer an Inquiry Project NumberDescriptionDept. Number 155Payroll257 498Widgets632 226Sales manager598 Dept. NumberDept. NameManager SSN 257Accounting421-55-99993 632Manufacturing765-00-3192 598Marketing098-40-1370 SSNLast NameFirst NameHire DateDept. Number 005-10-6321JohnsFrancine10-7-65257 549-77-1001BuckleyBill2-17-79650 098-40-1370FiskeSteven1-5-85598