A data model, called the entity-relationship model, is proposed. This model incorporates some of the important semantic information about the real world. A special diagrammatic technique is introduced as a tool for database design. An example of database design and description using the model and the diagrammatic technique is given. Some implications for data integrity, infor-mation retrieval, and data manipulation are discussed. The entity-relationship model can be used as a basis for unification of different views of data: t,he network model, the relational model, and the entity set model. Semantic ambiguities in these models are analyzed. Possible ways to derive their views of data from the entity-relationship model are presented. Key Words and Phrases: database design, logical view of data, semantics of data, data models, entity-relationship model, relational model, Data Base Task Group, network model, entity set

Successful communication of ideas has been and will continue to be a limiting factor in man's endeavors to survive and to better his life. The invention of algebra, essentially a graphic technique for communicating truths with respect to classes of arithmetic statements, broke the bond that slowed the development of mathematics. Whereas "12+ 13=25 ' ' and "3+7 = 10 " and "14+(-2) = 12" are arithmetic statements, "a+b=c ' ' is an algebraic statement. In particular, it is an algebraic statement controlling an entire class of arithmetic statements such as those listed. Data Structure Diagrams The Data Structure Diagram is also a graphic technique. It is based on a type of notation dealing with classes--specifically, with classes of entities and the classes of sets that relate them. For example, individual people and automobiles

ABSTRACT: The large, integrated data banks of the future will contain many relations of various degrees in stored form. It will not be unusual for this set of stored relations to be redundant. Two types of redundancy are defined and discussed. One type may be employed to improve accessibility of certain kinds of information which happen to be in great demand. When either type of redundancy exists, those responsible for control of the data bank should know about it and have some means of detecting any “logical ” inconsistencies in the total set of stored relations. Consistency checking might be helpful in tracking down unauthorized (and possibly fraudulent) changes in the data bank contents.