Business Rules and Data Models Essay

692 WordsOct 13, 20143 Pages
Business Rules and Data Models Strayer University CIS-111 Prof. A database is a structure that contains information about many different categories of information and about the relationships between those categories (Pratt & Adamsk 2010). Database objects are entities that exist within a database to support operations such as storing, retrieving and manipulating data. Organizations use large amounts of data and database management system to store and transform data into information to support making decisions. A database management system consists of the following three elements: 1. The physical database: the collection of files that contain the data. 2. The database engine: the software that makes it possible to…show more content…
An entity is a distinguishable object in the enterprise. An entity has attributes that describe the properties of the entity. For example, a course is an object in the student information system. The course number, title, credits, and prerequisites are the attributes for the course. All the courses have same type of attributes. A collection of entities of the same attributes is called an entity set. Since each entity is distinct, no two entities can have the same values on the attributes. Each entity class has an attribute or a set of attributes that can be used to uniquely identify the entities. In case there are several keys in the entity class, we can designate one as the primary key. For example, we can designate the course title to be the key, assume that every course has a different title. A composite attribute is an attribute that is composed of two or more sub-attributes. For example, the Student entity class has the address attribute that consists of street, city, state, and zipcode. A multivalued attribute is an attribute that may consist of a set of values. For example, the Course entity class has the prerequisites attribute. A course may have several prerequisites. Therefore, the prerequisites attribute is a multivalued attribute. A derived attribute is an attribute that can be derived or calculated from the database. A derived attribute should not be stored in the database. For example, we may add an
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