For Tim and Jim to comprehend the entities I will provide an explanation for each entity as well as entity name, owner, definition, and attributes and domain and relationships. Continually re-examine definitions to make sure they are clear, complete all vocabularies defined, concise that is brief and to the point, and never ambiguous. Use example to illustrate the terminologies since diagrams provide easy way of understanding.
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Entities are perceptions within the data model. Each entity is characterized by a box within the entity-relationship diagram. Entities are conceptual concepts, each representing one or more cases of the concept under discussion. An entity might be taken as a container that embraces all of the instances of a concept in a system. Entities are correspondent to database charts in a relational database, with each table’s row representing a case of that entity. Example School and Students are two entities where students must belong to at least a school.
An attribute is a descriptor or property of an entity, for instance, Customer Name is an element or attribute of the entity Customer. Each attribute ought to have a description and a name. An attribute depiction is a short description that conveys how the proper attribute reflects the real-world quality of interest. Descriptive Attributes, declare what characteristic contained by all instances of the instance is captured by this feature. Naming Attributes, identify the type of the name, the association that registers, assigns, or controls the name, and the degree to which the element can be used as fraction of the identifier. Referential Attributes such as foreign keys, state the connection being captured in the database model by the referential attribute (Harrington, 2009).
In database technology, domain is the description of an attribute's acceptable values. The physical explanation is a set of ideals the attribute can contain, and the logical or semantic description is the connotation of the attribute.
Provide an account for each relationship in the database model. The description must explain the connection and accurately enlighten the reader of the character of the relationship between two entities.
Document the association cardinality: one-to-many, one-to-one, many-to-many. Identify any integrity constraints. Example: If an Employee occurrence is removed, its Dependents occurrences ought to be deleted. Document the association dependencies: optional, mandatory, contingent. Illustrate relationship combinations: exclusive OR, inclusive OR, AND (Borysowich, 2007).
In Conclusion, the database model descriptions will require Entity-Relationship Diagram (ERD) for better understanding. A domain is also specified, which is the description of an attribute’s acceptable values. Attributes describe the properties of entities. The entries are the perceptions in a data model. A data model provides document association cardinality.
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