May 2002
Beginner to intermediate
448 pages
13h 18m
English
Content preview from Geographic Information Systems: An Introduction, 3rd Edition
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17.9 Developing a Logical Data Model
In the computer sciences, data modeling is considered part of the development of a data processing system. This view is common but not always correct. The development of a logical data model should not be linked to any particular technology, but should be devised by professionals who are expert in the field of application involved. It is therefore most natural to place this activity within organizational development.
Data models are discussed in detail in Chapters 3, 4, and 5. To summarize: Data models comprise objects, specified by five parameters: object type, geometry, attributes, relations, and quality. These parameters should be described in a data dictionary. The procedure for data structuring includes several topics discussed in Chapter 12:
- Defining applications
- Stipulating constraints, tasks, and requirements
- Ranking according to benefit and cost
- Descriptions of attributes
- Coordination of conditions and definitions
- Choice of geometric representation: raster or vector, points, lines, and surfaces
- Descriptions of relations between objects
- Quality requirements based on cost-benefit analysis: geometric accuracy, updating frequency, completeness and resolution, geographic coverage, logical consistency
- Coding of data with respect to identity, object types, and attribute values
A good data model is part of the specification of a data processing system, not the result of it.
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