For structured data type, use screen shot to display the structure. (1) Print the logical and relation models diagram to pdf files. (k) Engineer the logical model into relational model. (1) Identify mechanism for enforcing class-subclass relationships. For composite attributes like name and address, define a new structured data type. (i) If you have enough information from the description, identify the datatype for each attribute. However, we often we introduce a surrogate key for the associative entity which becomes the unique identifier for the associative entity.
In many cases, the associative entity will "inherit the attribute" of the entities involved in the original many-to-many relationship (or higher order relationships.) The combination of the inherited attributes can be used to enforce the uniqueness condition for associative entity. Take extra care in identifying attributes for associative entities. (h) Define associative entities to resolve many to many or higher order relationships. (g) Identify attributes associated with the relationships. Of course, we can rename the inherited attribute. In Oracle data modeler, a one to many relationship causes the primary key of entity on one side to become an attribute of the entity on many side. (1) Identify attributes that will used to enforce referential integrity rules. Select the attribute(s) that will be used to enforce uniqueness. (e) For each entity, identify the attributes that describe the entity. (d) Identify cardinality for each relationship. (c) Although Data Modeler resolves many-to-many binary relationships when building relational model, I would suggest that you get into habit of resolving them in the logical model. So if you are dealing with a ternary (or higher) relationship (e.g., a sales event brings a customer, a product, and a sales person together) you would introduce an "associative entity" and then define binary relationships between the original entities and the newly defined associative entity. In Data Modeler, we can draw only binary relationship and unary relationships.
(b) Resolve ternary or higher order relationship by introducing associative entities. If necessary, rewrite business rule so that each rule can be implemented either as a relationship or as a constrain that can be checked at data entry or update. You should follow a successive refinement approach: (a) Identify entities and relationships between them. Transcribed image text: Use Oracle Data Modeler to Draw logical E-R Diagrams for the following exercises from the textbook.
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