1. 8/28/97Information Organization and Retrieval Database Design University of California, Berkeley School of Information Management and Systems SIMS 202: Information Organization and Retrieval

2. 8/28/97Information Organization and Retrieval Review Database Data Models Database Design Process Basics of ER Diagrams

3. 8/28/97Information Organization and Retrieval Database Data Models Hierarchical Model –Similar to data structures in programming languages. Books (id, title) PublisherSubjects Authors (first, last)

4. 8/28/97Information Organization and Retrieval Database Data Models Network Model –Provides for single entries of data and navigational “links” through chains of data. SubjectsBooks Authors Publishers

5. 8/28/97Information Organization and Retrieval Database Data Models Relational Model –Provides a conceptually simple model for data as relations (typically considered “tables”) with all data visible.

6. 8/28/97Information Organization and Retrieval Database Data Models Object Oriented Data Model –Encapsulates data and operations as “Objects” Books (id, title) PublisherSubjects Authors (first, last)

7. 8/28/97Information Organization and Retrieval Database Design Process Conceptual Model Logical Model External Model Conceptual requirements Conceptual requirements Conceptual requirements Conceptual requirements Application 1 Application 2Application 3Application 4 Application 2 Application 3 Application 4 External Model External Model External Model Internal Model

8. 8/28/97Information Organization and Retrieval Database Design Process Conceptual Model –Merge the collective needs of all applications –Determine what Entities are being used Some object about which information is to maintained –What are the Attributes of those entities? Properties or characteristics of the entity What attributes uniquely identify the entity –What are the Relationships between entities How the entities interact with each other?

9. 8/28/97Information Organization and Retrieval Developing a Conceptual Model Overall view of the database that integrates all the needed information discovered during the requirements analysis. Elements of the Conceptual Model are represented by diagrams, Entity- Relationship or ER Diagrams, that show the meanings and relationships of those elements independent of any particular database systems or implementation details.

10. 8/28/97Information Organization and Retrieval Entity An Entity is an object in the real world (or even imaginary worlds) about which we want or need to maintain information –Persons (e.g.: customers in a business, employees, authors) –Things (e.g.: purchase orders, meetings, parts, companies) Employee

11. 8/28/97Information Organization and Retrieval Attributes Attributes are the significant properties or characteristics of an entity that help identify it and provide the information needed to interact with it or use it. (This is the Metadata for the entities.) Employee Last Middle First Name SSN Age Birthdate Projects

12. 8/28/97Information Organization and Retrieval Relationships Relationships are the associations between entities. They can involve one or more entities and belong to particular relationship types Examples derived from David R. McClanahan “Conceptual Design” DBMS Magazine January 1992, and “Hands-on Design”, February 1992.

13. 8/28/97Information Organization and Retrieval Relationships Class Attends Student Part Supplies project parts Supplier Project

14. 8/28/97Information Organization and Retrieval Types of Relationships Concerned only with cardinality of relationship Truck Assigned Employee Project Assigned Employee Project Assigned Employee 11 n n 1 m

15. 8/28/97Information Organization and Retrieval More Complex Relationships Project Evaluation Employee Manager 1/n/n 1/1/1 n/n/1 Manages Employee Project Assigned Employee 4(2-10)1 SSNProjectDate Manages Is Managed By 1 n

16. 8/28/97Information Organization and Retrieval Today More on Entity-Relationship Diagrams Designing a database

17. 8/28/97Information Organization and Retrieval Weak Entities Owe existence entirely to another entity Order-line Contains Order Invoice # Part# Rep# QuantityInvoice#

18. 8/28/97Information Organization and Retrieval Supertype and Subtype Entities Clerk Is one of Sales-rep Invoice Other Employee Sold Manages

19. 8/28/97Information Organization and Retrieval Many to Many Relationships Employee Project Is Assigned Project Assignment Assigned SSN Proj# SSN Proj# Hours

20. 8/28/97Information Organization and Retrieval Developing a Conceptual Model We will look at a small business Assume that we have done interviews with the business and found out the following information about the forms used and types of information kept in files and used for business operations...

21. 8/28/97Information Organization and Retrieval Primary Business Operations The business sells parts to customers. –Each part has: A part number, A selling price, A description of the part, The count of the part currently in stock.

22. 8/28/97Information Organization and Retrieval Business Operations (cont.) Each sale is on an invoice to one customer. –Invoices contain: Line items for each part ordered, Total amount due for the invoice, Customer information: –Company name, address, and an ID number. –Invoices are written up by one sales representative, who is credited with the sale Sales reps are paid a 5% commission on sales.

23. 8/28/97Information Organization and Retrieval Business Operations (cont.) Information must be kept on inventory of parts. There are multiple suppliers of parts: –The prices charged by different suppliers for a given part may be different. This is the Cost of the part.

24. 8/28/97Information Organization and Retrieval Business Operations (cont.) Employee information includes: –Name, –Social Security Number, –Employee ID number, –Address, –Position. Hourly wages must be tracked for all employees (except sales reps).

25. 8/28/97Information Organization and Retrieval Business Operations (cont.) One account is kept for each customer to track charges, payments, and the current balance. The company needs to know if an order has been shipped. The accounting department must know which invoices have been paid. The total sales for each sales rep must be calculated.

26. 8/28/97Information Organization and Retrieval Business Operations (cont.) We must know if a part is in stock at the company or on order from a supplier. Each hourly employee generates a time-card every Monday morning. Sales Reps don’t turn in time-cards, just their total sales. All employees are paid weekly by check. We need a report each Monday telling us what each employee should be paid for the previous week.

27. 8/28/97Information Organization and Retrieval Entities Customer Invoice Employee Inventory Supplier Account Sales Rep Parts Timecard Check

28. 8/28/97Information Organization and Retrieval Functional areas Ordering Inventory Supplies Shipping Personnel Payroll We will concentrate on Ordering and Inventory

29. 8/28/97Information Organization and Retrieval Ordering Invoice Rep-cust invoice Sales-Rep Customer Simple Ternary Relationship

30. 8/28/97Information Organization and Retrieval Ordering Invoice Orders Customer Cust# Writes Sales-Rep Invoice# Rep# Parts Repeating attribute

31. 8/28/97Information Organization and Retrieval Ordering Normalization Orders Customer Cust# Invoice Writes Sales-Rep Invoice# Rep# Line-Item Contains Part# QuantityInvoice# Cust#

32. 8/28/97Information Organization and Retrieval Parts and Suppliers Part Supplies Supplier Company# Includes Line-Item Part# Count Price Invoice# mn Is this correct? Where does Price belong?

33. 8/28/97Information Organization and Retrieval Parts and Suppliers (alternative 2) Company# Contains Line-Item Part#Invoice# Part Part# Count Price n m Supplier Company# Offers Supplied-Part Part# Cost Supplies Intersection Entity

34. 8/28/97Information Organization and Retrieval Parts and Suppliers (Alternative 3) Company# Contains Line-Item Part#Invoice# Part Part# Count Price Supplier Company# Supplies Supplied-Part Part# Cost

35. 8/28/97Information Organization and Retrieval Parts and Suppliers (Alternative Notation 4) Company# Contains Line-Item Part#Invoice# Part Part# Count Price m Supplier Company# Part# Cost Supplying

36. 8/28/97Information Organization and Retrieval Parts and Suppliers (Alternative Notation 5) Part Part# Count Price m Supplier Company# Cost Supplies

37. 8/28/97Information Organization and Retrieval ER Model Orders Customer Cust# Invoice Writes Sales-Rep Invoice# Sales Rep# Line-Item Contains Part# QuantityInvoice# Cust# Contains Part Part#Count Price Supplier Company# Ordered Part Hourly Employee ISA Emp# Wage Company# Part#Cost Supplied Part Has On-Order Supplies Company# Part#Quantity

38. 8/28/97Information Organization and Retrieval Next Time More on normalization Effectiveness and Efficiency criteria for database designs Advantages and failings of DBMS technology