Single Elimination – only one moves forward after comparison Thorough Comparison – takes into account all comparisons, choose one with the most wins or higher score after filling in chart DECISION MAKING TECHNIQUES
Decision Matrix : compare all alternatives against all criteria by scoring each, i.e. 1-10, where higher number is better this is widely used in business this considers all criteria to be of equal importance if all criteria are not of equal importance, then use a weighted average when combining scores across criteria, by, assigning percent weights across criteria that must sum to 100% then multiplying criteria weight times score then sum to get total score Proposal 1 = (6*.1) + (8*.2) + (4*.3) + (7*.1) + (8*.3) = 6.5 Proposal 2 = (8*.1) + (6*.2) + (5*.3) + (8*.1) + (8*.3) = 6.7 Proposal 3 = (4*.1) + (4*.2) + (6*.3) + (6*.1) + (9*.3) = 6.3 Proposal 4 = (1*.1) + (8*.2) + (7*.3) + (6*.1) + (9*.3) = 7.1 DECISION MAKING TECHNIQUES
Entity Something about which data needs to be kept Can be a thing or event Entities end up as a table in a database Record, or row, in a table is called an Instance of the Entity All the attributes in an entity should be completely determined by the entity instance’s primary key ERD – Entity Relationship Diagram The process of creating an ERD is called Database Modeling An ERD does not show how data is converted or processed to information in an Information System An ERD shows the relationships between the data REVIEW OF ENTITY & ERD
ENTITY CARDINALITY Cardinality quantifies an Entity Relationship Cardinality is the maximum number of times that an instance of an entity (table) can be associated with instances of another entity (table) Modality is the minimum number of times that an instance of an entity can be associated with instances of another entity
ENTITY RELATIONSHIP DIAGRAM (ERD) (ALTHOUGH IT IS INCOMPLETE)
Associative Entities The database relational model does not offer direct support to many-to- many relationships , even though such relationships happen frequently in the realm that is being modeled. An associative entity is added to the ERD model to resolve a many-to- many relationship between two entities. An associative entity is a relationship turned into an entity . An Associative entity is also called an Intersection Entity or a Linking Table ASSOCIATIVE ENTITIES
ASSOCIATIVE ENTITIES (CONT’D) We follow a rule in ERDs… Remove all many-to-many relationships by introducing associative entities A cardinality = many A modality = one B cardinality = many B modality = one Entity B Entity A A cardinality = many A modality = one B cardinality = many B modality = one AE cardinality = one AE modality = one AE cardinality = one AE modality = one Entity B Entity A Associative Entity
ENTITY RELATIONSHIP DIAGRAM Course Section Instructor One-to-Many Relationships: • Each course has many sections • Each instructor teaches many sections
ENTITY RELATIONSHIP DIAGRAM Course Section Instructor Teaching Assistant Student
ASSOCIATIVE ENTITY OR LINKING TABLE Associative Table
ENTITY RELATIONSHIP DIAGRAM:
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