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Thread: ERM versus UML

  1. #1
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    ERM versus UML

    Hi, im wondering if people could share thoughts with me as to why ER Modelling is generally a better modelling technology than UML or vice versa, or in which areas each is stronger than the other, and also maybe point me in the right direction to attain some articles or journals or a forum relating. I am conducting some research on the two (ERM & UML) any would value any oppinions put forward.

    thankyou.

  2. #2
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    Sure, I'd be happy to chat with you. What all has your instructor covered in class so far?

    -PatP

  3. #3
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    Hi pat, im trying to generally discover which areas either one are stronger or more appropriate to use, could you inform me what are the key strengths and weaknesses of both ERM and UML?

  4. #4
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    Often the key strength/weakness is the same thing. In other words, a single characteristic can be a strength in one circumstance and a weakness in another.

    As an example, UML is a generic modeling tool while ER is a database specific modeling tool. If you want to model OOP classes, that is an advantage for UML. If you want to model databases, that is an advantage for ER.

    If you think about this compared to "real world" tools, a jeweler's saw is a very specialized tool, while a chainsaw is a very generic tool. In an abstract sense, the specialized versus generic doesn't matter, they are both saws and it isn't relevant. However, if you want to cut down a tree, the jewler's saw isn't much good... If you want to cut a ring off of your grandmother's swollen finger, the chainsaw probably wouldn't be your first choice either!

    If you start to look at the problem from this perspective, you'll probably find some obvious differences between the two (UML and ER), that makes one much better suited for a given task than the other.

    -PatP

  5. #5
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    Hi pat, ive been reading upon chris dates thoughts regarding OO, and seem to understanding what message he's trying to get accross. When u say that UML is a generic tool, what other generic tools (data modelling languages) are out there? and are worth gaining an understanding or taking a look?

  6. #6
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    You may want to look at ORM (Object Role Modeling)

  7. #7
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    Standards are wonderful things... If you don't like any of the existing standards, you can go out and "grow your own" either from the current crop or starting from scratch.

    ER actually has many flavors. I prefer IDE1FX, others prefer "crows foot", others prefer SERM.

    UML takes the "all things to all people" approach. It is struggling to encompass the universe. Due to that, there are lots of splinter diagraming disciplines that are reasonably closely related.

    There are a number of older modeling systems, and some newer ones that all have their own distinct "personalities" and bring unique benefits and drawbacks to the table. You'll have to find one (or several as your modeling needs expand) that works for you.

    -PatP

  8. #8
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    Is IDE1FX specifically geared for database construction (as it is ER) or is it more general, and can it be used like UML?

  9. #9
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    IDEF1X is purely database oriented, although it is part of a larger design methodology specified by FIPS 184 and related publications that incorporates most of the DP/IT universe.

    -PatP

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