DÂY LƯNG & VÍ DA CHẤT LƯỢNG CAO THƯƠNG HIỆU H2


Designing the GIS Database Schema

Database designers use the word schema to refer to the diagram and documents
that lay out the structure of the database and the relationships that exist between
elements of the database.A schema is like a blueprint for a database that tells a knowledgeable builder exactly how to construct it. Naturally, designers spend a lot of time thinking about the schema.This work comes before worrying too much about the
exact content of tables and even before design concerns for the spatial data. Rushing into building a database without laying out your schema is like trying to build a house without a set of plans; it might stand up for a while, but it will not be as useful as it could be. The tools that assist in the construction of these schema are called computer assisted software engineering (CASE) tools.These same tools are used to design the structure of complex computer programs as well as databases, and most programmers know how to use them. Many in the GIS world do not, but it is usually possible to design your database with paper and pencil, and some database designers still work this way.The ability to erase entire tables, delete relationships, add relationships, and so on, is sometimes easier with pencil and paper or on a whiteboard than mastering a new set of tools. One of the problems with GIS is that it appears to force you to develop areas of specialization and skill that you didn’t have before. Sometimes it just takes too long to learn the new tools, so feel free to use simpler ones you have mastered instead of new tools that do basically the same thing...


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