The most widely used method of rapid application development is one of the prototype。 The prototype system is a method of iterative development process, analysts and users through close co-operation, continuing to revise the system will eventually convert all the needs of a working system。 Figure 6 shows prototype of the process。 In this diagram we contains notes, briefly describes each stage of the prototype of the database development activities。 Normally, when  information systems problems were identified, tried only a rough concept of data modeling。 In the development of the initial prototype, the design of the user wants to display and statements, and that any new database needs and define a term prototype database。 This is usually a new database, copy the part of the existing system, but might also added some new content。 When the need for new content, these elements are usually from external data sources, such as market research data, the general economic indicators or industry standards。

When a prototype of a new version to repeat the achievement and maintenance of database activities。 Usually only a minimum level of security and integrity control, because at this time the focus is as soon as possible to produce a prototype version can be used。 But document management project also deferred to the final, only be used in the delivery of user training。 Finally, once constructed an acceptable prototype, developers, and users will be the final decision of whether to prototype delivery and the use of the database。 If the system (including database) efficiency is very low, then the system and database will be re-programming and re-organization in order to achieve the desired performance。

Along with visual programming tools (such as Visual Basic, Java, Visual C + + and fourth generation language) increasingly popular use of visual programming tools can easily change the user interface with the system, the prototype is becoming the

choice of system development methodology。 Customers using the prototype method statements and show changes to the content and layout is quite easy。 In the process, the new database needs were identified, so it is the development of the use of the existing database should be amended。 There is even the possibility of a need for a new database system prototype method, in such circumstances, when the system  demand in the iterative process of development in the ever-changing needs access to sample data, the construction or reconstruction of the database prototype。

3database development of the three-tier architecture model

In this article on the front of the database development process mentioned in the interpretation of a system development project on the establishment of the several different, but related database view or model:

●conceptual model (in the analysis stage of the establishment)。

●external model or user view (in the analysis phase and the establishment of logical design phase)。

●physical model or internal model (in the physical design phase of the establishment)。

Figure 7 describes the database view that the relationship between the three, it is important to remember that they are the same organizations database view or model。 In other words, each organization has a database of the physical model, a concept model and one or more users view。 Therefore, the three-tier architecture model using the same data set observe the different ways definition database。

Concept models on the full database structure, has nothing to do with the technical specifications。 Conceptual model definition do not involve the entire database data stored in the computer how the secondary memory。 Usually, the conceptual model by entities - links (E-R) map or object modeling symbols such a graphical format to describe, we have this type of concept model called the  data model。 In addition, the conceptual model specification as a metadata stored in the database or data dictionary。