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26 Cards in this Set
- Front
- Back
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Define Supertype and give an example
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a generic entity that has a relationship with one or more subtypes
(example: Employee) |
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Define Subtype and give an example
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a subgrouping of a supertype entity that is meaningful to an organization
(example: Hourly Employee) |
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What are the Two Processes to Develop Supertype/Subtypes
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Generalization
The process of defining a more general entity type from a set of more specialized entity types A “bottom-up” approach Specialization The process of defining one or more subtypes of a general entity based on distinguishing attri-butes or relationships A “top-down” approach |
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What are Business rules
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A statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behavior of the business.
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Why are business rules good
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Allow faster application development
Reduce system maintenance Provide faster response to business changes Promote ease of use of database applications |
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A Good Data Name Is
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Related to business, not technical, characteristics
Meaningful and self-documenting Unique Readable Composed of words from an approved list Repeatable Follows standard syntax |
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What Should an Entity Be and not be?
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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 SHOULD NOT BE: A user of the database system An output of the database system (e.g., a report) |
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What is an attribute
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property or characteristic of an entity or relationship type
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What is an Identifier (Key)
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an attribute (or combination of attributes) that uniquely identifies individual instances of an entity type
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What is an Associative Entity
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combination of relationship and entity
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What are Strong entities
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exist independently of other types of entities
has its own unique identifier identifier underlined with single line |
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What are Weak entities
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dependent on a strong entity (identifying owner)…cannot exist on its own
does not have a unique identifier (only a partial identifier) partial identifier underlined with double line entity box has double line |
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When should a relationship with attributes instead be an associative entity?
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All relationships for the associative entity should be many
The associative entity could have meaning independent of the other entities The associative entity preferably has a unique identifier, and should also have other attributes The associative entity may participate in other relationships other than the entities of the associated relationship Ternary relationships should be converted to associative entities |
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What is an Enterprise Data Model
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an integrated view of the data produced and consumed across an entire organization. It incorporates an appropriate industry perspective.
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What is Top-Down Planning
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A methodology that attempts to gain a broad understanding of the information system needs of the entire organization
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What is Bottom-Up Planning
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A methodology that identifies and defines IS development projects based upon solving operational business problems or taking advantage of business opportunities
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What is an entity
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a person, place, object, event or concept about which an organization wishes to maintain data.
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What is an association
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a relationship between entities whose naming and notation capture fundamental business rules
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What is a database
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an organized collection of logically related data.
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What is data
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facts, text, images, sound, and video segments that have meaning in the users’ environment.
Structured: Unstructured: |
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What is metadata data
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data about data
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What are Disadvantages of File Processing
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Program-Data Dependence
All programs maintain metadata for each file they use Duplication of Data Different systems/programs have separate copies of the same data Limited Data Sharing No centralized control of data Lengthy Development Times Programmers must design their own file formats Excessive Program Maintenance 80% of information systems budget |
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What is good about the DATABASE Approach
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Central repository of shared data
Data is managed by a controlling agent Stored in a standardized, convenient form Requires a Database Management System (DBMS) form. |
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What is a Database Management system
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A software system that is used to create, maintain, and provide controlled access to user databases
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What is a Repository
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centralized storehouse of metadata
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What is master data management
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An approach to dealing with data duplication.
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