Databases Reference
In-Depth Information
VWDB, objects belonging to the same category have the same spatial and non-
spatial attributes as well as the same behaviors. Category hierarchies are defined
similarly to the class hierarchies in the object- oriented paradigm.
Now, it becomes clear that the VWDB database schema definition language
should have the following three sub-languages:
1.
A virtual world definition sub-language for an enterprise administrator to
describe a virtual world on the meta-level.
2.
A category definition sub-language for an enterprise administrator to
describe a category hierarchy.
3.
A spatial domain definition sub-language to describe a set of spatial domain
definitions to be used in the category definition above.
3.2
A Brief Description of the VWDB Schema Definition Language
In this section, we briefly show the syntax of the VWDB virtual world definition
sub- language, the VWDB category definition sub-language, and the VWDB spatial
domain definition sub-language.
3.2.1
The VWDB Virtual World Definition Sub-Language
The following shows a basic syntax of the VWDB virtual world definition sub-
language:
In <Virtual World Name>, a VWDB database administrator or designer specifies
the name of a virtual world that he/she wants to define. The designer specifies a
whole set of category names to be used in the virtual world. Precise definitions of
the categories are given using the VWDB category definition sub-language.
3.2.2
The VWDB Category Definition Sub-language
Using this sub-language, categories are defined in the following manner:
