Hi,

I'm a student currently working on my final year project. I came accross this topic of Generalization Hierarchy at http://www.utexas.edu/its/windows/da...erarchies.html but the article was not very detailed.

I need to be sure if the entity 'artefact', which could be anything ranging from paintings to furniture, can suitably used here. If so, how can I apply that into relational databases i.e: steps to make generalized tables (if that's what they can be called)

Pls point to some source of info too - like, where do I begin?

Thanks

I think the answer to your question, if a generlaization hierarchy could be used for storing information about artefacts, depends on what information you want to store. To answer this accurately someone would need to know the requirements of your system including what attributes of an artefact you intend to record about each instance of an artefact.

For example, if for each artefact you only want to track it's unique name and date of creation you would only need a single entity with these two attributes.

Alternately, if you wanted to track each artefacts unique name and date of creation and then other information specific to the type of artefact, a generalization hierarchy may be your best choice. For example, for artefacts that are paintings you might want to track the artist and type of paint used, while for furniture you would want to track the material used and style. To extend this further, with this method you could even track different attributes of sofas and chairs (as subtypes of furniture). Where for a sofa you would track the size and for a chair, maybe the number of legs.

To create tables for the generalization hierarchy described above:

artefacts
---------
name (PK)
creationDate

paintings
---------
name (PK) (FK references artefacts.name)
artist
paintType

furniture
--------
name (PK) (FK references artefacts.name)
material
style

sofas
-----
name (PK) (FK references furniture.name)
size

chairs
------
name (PK) (FK references furniture.name)
numberOfLegs

Below is an illustration of the model.

Note the inclusion of discriminators, artefact_type and furniture_type.