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Database Modeling & Design Fourth Edition- P50

Database Modeling & Design Fourth Edition- P50: Database technology has evolved rapidly in the three decades since the rise and eventual dominance of relational database systems. While many specialized database systems (object-oriented, spatial, multimedia, etc.) have found substantial user communities in the science and engineering fields, relational systems remain the dominant database technology for business enterprises. | 232 Glossary X and A are either simple or composite attributes data items X must be a superkey in that table. This is a strong form of 3NF and is the basis for most practical normalization methodologies. candidate key Any subset of the attributes data items in a superkey that is also a superkey and is not reducible to another superkey. CASE tool Computer-aided software engineering tool a software design tool to assist in the logical design of large or complex databases. examples include ERwin Data Modeler and Rational Rose using UML. class A concept in a real-world system represented by a noun in UML similar to an entity in the ER model. class diagram UML A conceptual data model a model of the static relationships between data elements of a system similar to an ER diagram . completeness constraint Double-line symbol connecting a supertype entity with the subtypes to designate that the listed subtype entities represent a complete set of possible subtypes. composition A relationship between one class and a group of other classes in UML the class at the diamond aggregate end of the relationship is composed of the class es at the small component end similar to aggregation in the ER model. conceptual data model An organization of data that describes the relationships among the primitive data elements. For example in the ER model it is a diagram of the entities their relationships and their attributes. connectivity of a relationship A constraint on the count of the number of associated entity occurrences in a relationship either one or many. data item The basic component of a data record in a file or database table the smallest unit of information that has meaning in the real world. Examples include customer lastname address and identification number. data model An organization of data that describes the relationships among primitive and composite data elements. data warehouse A large repository of historical data that can be integrated for decision support. database A .