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27 Cards in this Set

  • Front
  • Back
Detailed model that captures the structure of organizational data while being independent of a database management system or any other implementation consideration
Conceptual Data Model
How are DFDs and ER Diagrams related?
Data Stores in DFDs correspond to Entity types in an ER diagram
-Purpose is to show rules about the meaning and interrelationship of data
-Creates accurate Entity-Relationship(ER) diagrams
Conceptual Data Modeling
What methods are used to collect information for conceptual data modeling?
Interviewing, questionairres, and JAD
1) Develop a data model for the system being replaced
2) A new conceptual data model is built that includes all the requirements of the new system
3) Design: the conceptual data model is translated into physical design
4) Project repository links all design and data modeling steps performed during SDLC
Process of Conceptual Data Modeling
Data modeling derived from an intimate understanding of the business
Top-down Information Gathering
Data model is derived by reviewing specifications and business documents
Bottom-up Information Gathering
Detailed, logical representation of the entities, associations, and data elements for an organization or business
Entity-Relationship (ER) Diagram
A person, place, object, event, or concept in the user environment, about which, the organization wishes to maintain data
A collection of entities that share common properties or characteristics
Entity Type
Single occurrence of an entity type
Entity Instance
A property or characteristic of an entity that is of interest to the organization
An attribute or set of attributes that distinguishes one entity instance from another instance of the same entity type
Candidate Key
Candidate key that uniquely identifies an instance of an entity type
Attribute that cannot be broken down into smaller components
Simple Attribute
Attribute that can be broken down into its component parts
Composite Attribute
Attribute with a single value
Single-valued attribute
Attribute that may have more than one value for a given entity instance
Multi-valued Attribute
An attribute whose value can be figured out from related attribute values
Derived Attribute
1) Use attribute(s) that will not change over time
2) Must never be empty "null"
3) Avoid intelligent keys: structure of key indicates classificatio, location
4) Try to use single attribute keys
How to select an identifier
An association between instances of one or more entity types of interest to the organization (shown as a VERB)
Number of entity types in a relationship:
Degree 1 "Bill of Materials" =
Degree 2 Most common =
Degree 3 =
The number of instances of one entity that can (or must) be associated with each instance of another entity
Relationship name is a verb
Make names explicit
How to Name Relationships
Definition explains what action is being taken and why it is important
Give examples to clarify the action
Optional participation should be explained
Explain reasons for any explicit maximum cardinality
How to Define relationships
Entity that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances
Associative Entity
1) All relationships for the associative entity should be many
2) The associative entity could have meaning independent of other entities
3) Associative entity preferably has a unique identifier, and should also have other attributes
4) May be participating in other relationships other than the entities of the associated relationship
5) Ternary relationships should be converted to associative entities
When a relationship with attributes should be an associative entity