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

ly this simulation model is just a M/M/s queue.] This bank simulation program consists of a teller resource and two process specification procedures. These procedures provide a script or template for created processes. The Generator process (the single process created from the Generator process specification procedure) is used to create Poisson arrivals of Customer processes. The Customer process specification procedure encodes a script for a typical customer. A customer requests a teller. If one is not available, the customer waits in the teller queue. Once the customer has a teller, he is served for an exponentially distributed amount of time. Finally, the customer relinquishes the teller and leaves the bank. [Note, Wirth's InOut I/O module is somewhat weak and inconvenient, so we wrote our own (PascalIO) whose flavor is closer to I/O in Pascal. The letter after the word WRITE is the first letter of the data type being written.] After the program listing, output results generated fro...

First order logic provides a means of integrating the speci#cation and prototyping of interactive systems. It can describe graphical images in a declarative and order independent manner. It supports the de#nition of abstract devices which avoid the complexity of representing `raw' input from a variety of physical devices. The following pages show how such techniques must be extended in order to prototype and reason about dynamic interaction with graphical interfaces. The incorporation of a temporal ordering into logical speci#cations provides a means of describing changes in the structure of graphical images. It can also identify the sequencing which may be implicit within speci#cations of interactive dialogues. This paper describes how PRELOG, a tool for Presenting and REndering LOGic speci#cations of interactive systems, has been extended to include a temporal logic interpreter.