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  1. #1
    Join Date
    Apr 2004
    Location
    KL
    Posts
    1

    Generalization Hierarchy help pls

    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
    Last edited by waipeng; 04-28-04 at 08:05.

  2. #2
    Join Date
    May 2004
    Posts
    5
    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

  3. #3
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    710
    Below is an illustration of the model.

    Note the inclusion of discriminators, artefact_type and furniture_type.
    Attached Thumbnails Attached Thumbnails 1 generalization.GIF  

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