Card Set Information

2012-03-12 01:03:09
IS410 exam1 chap1 chap2 chap3

IS410 exam1 chap1
Show Answers:

  1. define: database
    • an organized collection of logically related data
    • – storehouse of the data
  2. define: data
    stored representations of objects and events that have meaning and importance in the user's environment
  3. define: information
    data processed to increase knowledge in the person using the data
  4. Problems with Data Dependency
    • -Each application programmer must maintain their own data
    • -Each application program needs to include code for the metadata of each file
    • -Each application program must have its own processing routines for reading, inserting, updating and deleting data
    • -Lack of coordination and central control
    • -Non-standard file formats
    • -Waste of space to have duplicate data
    • -Causes more maintenance headaches
    • Biggest prob:
    • -When data changes in one file, could cause inconsistencies -Compromises data integrity
  5. define: metadata
    data that describes the properties and context of user data
  6. Database Management System (DBMS)
    • A software system that is used to create, maintain, and provide controlled access to user databases
    • – software for managing the database
  7. Advantages of the Database Approach
    • -program-data independence
    • -minimal data redundancy
    • -improved data consistency
    • -improved data sharing
    • -increased productivity of application development
    • -enforcement of standards-improved data quality
    • -improved data accessibility and responsiveness
    • -reduced program maintenance
    • -improved decision support
  8. Program-Data Dependence
    -All programs maintain metadata for each file they use
  9. Costs and Risks of the Database Approach
    • -new, specialized personnel
    • -installation and mgmt cost and complexity
    • -conversion costs
    • -need for explicit backup and recovery
    • -organizational conflict
  10. Components of the Database Environment
    • -CASE Tools
    • -Repository
    • -Database Management System (DBMS)
    • -Database
    • -Application Programs
    • -User Interface
    • -Data Administrators
    • -System Developers
    • -End Users
  11. CASE Tools
    – computer-aided software engineering
  12. Repository
    – centralized storehouse of metadata
  13. Application Programs
    – software using the data
  14. Data Administrators
    – personnel responsible for maintaining the database
  15. User Interface
    – text and graphical displays to users
  16. System Developers
    – personnel responsible for designing databases and software
  17. End Users
    -people who use the applications and databases
  18. Why NOT use File Systems instead of DB?
    • -Program-Data Dependence
    • -Duplication of Data
    • -Limited Data Sharing
    • -Lengthy Development Times
    • -Excessive Program Maintenance
  19. Information Systems Architecture (ISA)
    -Conceptual blueprint for organization’s desired information systems structure
  20. Components of Information Systems Architecture (ISA)
    • -data
    • -processes
    • -data network
    • -people
    • -events and points in time
    • -reasons
  21. Enterprise data model
    describes the high-level entities in an organization and the relationship between these entities
  22. three useful modeling techniques
    • Decomposition
    • Planning Matrixes
    • E-R diagram
  23. Decomposition
    breaking large tasks into smaller tasks in a hierachical structure chart
  24. Planning Matrixes
    • -Describe relationships between planning objects in the organization
    • -Function-to-data entity
  25. Two database development approaches
    • -System development life cycle
    • -Prototyping
  26. System Development Life Cycle
    • -the traditional methodology used to develop, maintain, and replace information systems
    • -Detailed, well-planned development process
    • -Time-consuming, but comprehensive
    • -Long development cycle
  27. prototyping
    • an iterative process of systems development in which requirements are converted to a working system that is continually revised through close work between analysts and users
    • Rapid application development (RAD) method
  28. Three database schema
    • External Schema
    • Conceptual Schema
    • Internal Schema
  29. Conceptual Schema
    • or data model
    • is a detailed specification of the overall structure of organizational data that is independent of any database management technology
    • a E-R diagram
  30. Internal Schema
    • consists of logical schemas: relational schema (tables, columns)
    • and physical schemas: implemented in a specific DBMS (column types, indexes)
  31. External Schema
    • -is the User Views, different by users
    • -Subsets of Conceptual Schema
    • -Can be determined from business-function/data entity matrices
    • -DBA determines schema for different users
  32. Guidelines in naming a data name
    • Must be:
    • -Related to business, not technical, characteristics
    • -Meaningful and self-documenting
    • -Unique
    • -Readable
    • -Composed of words from an approved list
    • -Repeatable
    • -Follow a standard syntax
  33. Term
    word or phrase with specific meaning
  34. Fact
    association between two or more terms
  35. Guidelines for good data definition
    • -Gathered in conjunction with systems requirements
    • -Accompanied by diagrams
    • -Iteratively created and refined
    • -Achieved by consensus
  36. Entity Type
    collection of entities (often corresponds to a table)
  37. Entity instance
    person, place, object, event, concept (often corresponds to a row in a table)
  38. What Should/Shouldn't an Entity Be?
    • -SHOULD BE:
    • -An object that will have many instances in the database
    • -An object that will be composed of multiple attributes
    • -An object that we are trying to model
    • -A user of the database system
    • -An output of the database system (e.g. a report)
  39. Attribute
    • property or characteristic of an entity type
    • E.g., customer’s address, name, phone number
  40. Identifier (Key)
    • An attribute (or combination of attributes) that uniquely identifies individual instances of an entity type
    • Represented by underlining attribute name.
  41. Characteristics of Identifiers
    • -Will not change in value (name?)
    • -Will not be optional (can not be address)
    • -Not multi-valued (not phone numbers)
    • -No intelligent identifiers (e.g. containing addresses that might change)
    • -Substitute new, simple keys for long, composite keys (cust_ID generated by DBMS vs. customer name + address)
  42. define: Relationship
    • An association representing an interaction among instances of entities that must be stored in the database (often as an event)
    • Use lines to link entities with relationship
  43. Unary Relationship
    • a relationship between the instances of a single entity type
    • e.g. an employee manages many employee
  44. Ternary relationship
    relationship between three entity types
  45. Cardinality of Relationships
    -Identifies number of entity instances of entity B associated with each entity instance of entity A
  46. One-to-One (1:1)
    Each entity A in the relationship will have exactly one related entity B and vice versa
  47. One-to-Many (1:M)
    • An entity on one side of the relationship can have many related entities, but an entity on the other side will have a maximum of one related entity
    • -Represented by crow’s foot sign at many entity side
  48. Many-to-Many (M:N)
    • -Entities on both sides of the relationship can have many related entities on the other side
    • -Represented by adding two crow’s foot sign
  49. Minimum Cardinality
    • -If zero, then optional, represented by a circle
    • -If one or more, then mandatory, represented by a vertical line
    • -Each entity may have different constraints
  50. Max Cardinality
    • -If 1, represented by a vertical line
    • -If more than 1, represented by crow’s foot.
    • -Mark in min, max order from the middle
  51. Strong entities
    • -Exist independently of other types of entities
    • -Has its own unique identifier
    • -Represented with single-line rectangle
  52. Weak entity
    • -Dependent on a strong entity…cannot exist on its own
    • -Does not have a unique identifier
    • -Represented with double-line rectangle
    • -Links strong entities to weak entities
  53. Associative Entities
    an entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationsip between those entit instances