The Logical & Physical Data Models

The logical data model is a business model and is known also as an ‘entity relationship diagram’ and how they relate to each other.

It is similar to a mental map of an entity (describing a car from a group) each car would have attributes such as a name, year made and the registration. The logical diagram would also show some form of distinctive attribute or a group of traits called a primary key that will describe exactly one entry within the particular entity.

A physical model is the ‘map’ from the logical model to the hardware.

The developer must be able to understand and use the physical model, the physical model for the person should include implementation details. These details can be things like data types and restrictions etc. The Difference between these two is that the physical model describes each entity in detail and how the model should be implemented whilst the logical model the entities for the models and how they are related to each other. The ER Model Describe the ER model and the classical notations used in this model

The Entity-Relationship Model (a logical fact that uniquely distinguishes each occurrence of an entity) is a way of representing the logical relationships of the entities using graphics in order to create operating programme i. e. database. The ER Model can be used as a basis for a group of different views of data such as the network model, the relational model and the entity set model. However the value or the data must never change.

Examples of ER Models Illustrate your understanding of the ER model using an example of your choice. Your example should have at least four related entities.

Explain your entities and their associations. What is java all about? Java is an innovative programming language that has become the language of choice for programs that need to run on a variety of computer systems. First of all java enables you to write small programs called applets. These are programs that you can embed in internet web pages to provide some intelligence. Being able to embed executable code in a web page introduces a vast range of exciting possibilities. Instead of being a passive presentation of text and graphics, a web page can be interactive in any way that you want.

You can include animations, games, interactive transaction processing – the possibilities are almost unlimited. Java also allows you to write large-scale application programs that you can run on any computer with an operating system environment in which the language is supported. This applies to the majority of computers in use today. You can even write programs that will work both as ordinary applications and as applets. Java has matured immensely in recent years, particularly with the introduction of java 2.

The breadth of function provided by the standard core java has grown incredibly. Java provides you with comprehensive facilities for building application with an interactive GUI, extensive image processing and graphics programming facilities, as well as support for accessing relational databases and communications with remote computers over a network. Release 1. 4 of java added a very important additional capability, the ability to read and write XML. Just about any kind of application can now be programmed effectively in java, with the implicit plus of complete portability.

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