Chapter 2 - Introduction to Database Development

• User Data
• Metadata (description of the structure of the data)
• Indexes (used for sorting and quick access)
• Application Metadata (stores the structure and format of user forms, reports, queries, etc.

1. Microsoft Access
2. Wall Data's SALSA
3. Borland's Paradox
4. Borland's dBase
5. Lotus Approach

• The Design Tools Subsystem (used by the developer)
  1. Table Creation Tool
  2. Form Creation Tool
  3. Query Creation Tool
  4. Report Creation Tool
  5. Procedural Language Compiler
• Run-Time Subsystem (used by the users)
  1. Form Processor
  2. Query Processor
  3. Report Writer
  4. Procedural Language Run Time
• The DBMS Engine (interface between the design tools and the run time subsystems)

• An Example of a Schema scenerio: The university wants to keep track of athletic equipment that has been checked out by the team captains
  
  1. TABLES:
     CAPTAIN(CAPTAIN_ID, CaptainName, Phone, Street, City, State, Zip)
     ITEM(ITEM_ID, Quantity, Description, DateOut, DateIn)
  2. RELATIONSHIPS: 1 Captain -> Many Items (1:N) Need to add CAPTAIN_ID to the ITEM
  3. DOMAINS: CAPTAIN_ID, ITEM_ID, and Quantity are Integer, others are Text
  4. BUSINESS RULES (Constraints):
     1. In order to check out equipment, the captain must have a local phone #.
     2. No captain may have more than 7 soccer balls checked out at one time.
     3. Captains must return all equipment within five days after the end of each semester.
     4. No captain may check out more equipment if he or she has any overdue.
• Creating Tables
  
  
• Defining Relationships
  In Access, use the Relationships Window to link the tables's keys and foreign keys

• Forms - most DBMS's have a form generation tool
  
  
• Queries
  1. query by example (QBE) - uses special table where fields are selected and constraints specified
  2. data access language (SQL) - requires "programming"
  3. query by form - constraints are entered into the form
• Reports
  
  
• Menus - pull-down Windows menus
• Application Programs - requires a programming language like Visual BASIC

• General Strategies
  A database is a model of the users' model of their business activities
  1. prototype - sample databases and applications that represent various aspects of the system to be created
  2. top-down development - proceeds from the general to the specific
  3. bottom-up development - starts with the specific
• Data Modeling
  1. Data Modeling as Inferencing (need to infer the model from what the users want
  2. Modeling in Multiuser Systems - more difficult: each user may have their own "view"
  3. Confusion About the Term Model - need to build a "user's data model" or "requirements data model"