spatial database design. sept 27

Question 1

explain the bottom up approach

Answer 1

• build DB from pre-existing data.

- quick to build.

Question 2

explain the top-down approach

Answer 2

-focused on needs.
-i.e. Tomlinson’s approach
information products>data themes>data layers>spatial and attribute characteristics.

Question 3

what are the 4 principles of data modelling according to yeung and hall?

Answer 3

• model choice
• levels of precision
• linkages to reality
• no single model can encapsulate all aspects

Question 4

what is a data model?

Answer 4

• mathematical representation of real world, description of entities and relationships. (i.e. raster vs vector)
• a framework that ensures consistency between entities. flexible and can adjust to change.

Question 5

what are the 4 lvls of data modelling?

Answer 5

• external
• conceptual
• logical
• physical

Question 6

explain external modelling

Answer 6

-users define what real world phenomena they want to model.

Question 7

what is conceptual modelling?

Answer 7

• synthesis of all external models

- schematic representation of the DB. defines what in real world is modelled

Question 8

what is logical modelling?

Answer 8

• structure of the database elements

- HOW the conceptual model is structured in the DBMS

Question 9

what is physical modelling?

Answer 9

-putting things in the right places in a DB, i.e. managing files, storage,

Question 10

What problems can a well’designed DB avoid?

Answer 10

• inability to extend the design to meet new needs
• unsupported application and/or query capabilities
• lack of integration w other apps
• additonal costs to revise DB