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  1. #1
    Join Date
    Mar 2004
    Posts
    64

    data modeling? ER model or UML

    Hello:

    I'm new to data modeling. I have some experience of creating ER model. And a little about UML modeling.

    I'm going to a new job as a DBA.

    What tool should I use?
    Should a DBA learn ER modeling or UML modeling?
    If the developer group use Rational rose, should the data analyst use Rational Rose too?

    Thanks for any suggestions.

  2. #2
    Join Date
    Feb 2004
    Posts
    108

    Re: data modeling? ER model or UML

    Originally posted by xcao
    What tool should I use?
    Should a DBA learn ER modeling or UML modeling?
    Tools should not matter. It's just a way of representing the conceptual design.
    Well .... dba .... the role totally depends on the company/job reqs. I have seen places where the dba is just ment for database and nothing beyond it. And I have seen places where the developer himself creates/specifies the dba specs.

    Good luck !

  3. #3
    Join Date
    Mar 2004
    Posts
    64

    tool

    Thank you. But what is the best data modeling tools.

    Any suggestions?

    Thanks

  4. #4
    Join Date
    Sep 2002
    Location
    UK
    Posts
    5,171

    Re: tool

    From what I've seen, UML doesn't add anything useful to data modelling - nor was it originally intended to, it is for OO software design primarily. But a way to emulate ERDs in UML has been kludged up, and fads being what they are it's probably as well to know it!

  5. #5
    Join Date
    Apr 2004
    Location
    Toronto, Ontario, Canada
    Posts
    4

    UML or ER for data modelling

    I have been a data modeller for many years. I have looked at UML as a tool for data modelling but it does not seem to add much. I have also looked at Rational Rose as a data modelling tool. My feeling is that you can use it as a data modelling tool, using the class diagram for the logical level, but that it is a clumsy tool compared to tools such as ERwin. I am not convinced that there is any particular benefit in using it even if the rest of the application is being designed using Rational Rose, but if it is a company standard go ahead and try. I am not particularly happy with the assumption that a class equals a table - it is certainly not a restriction that one should be rigid about.

    I am very interested in hearing from anyone who can tell me some of the advantages of using Rational as a common tool (if any).

  6. #6
    Join Date
    Dec 2003
    Location
    Tokyo Japan
    Posts
    26

    check this out

    Quote Originally Posted by fbrickhill
    I have been a data modeller for many years. I have looked at UML as a tool for data modelling but it does not seem to add much. I have also looked at Rational Rose as a data modelling tool. My feeling is that you can use it as a data modelling tool, using the class diagram for the logical level, but that it is a clumsy tool compared to tools such as ERwin. I am not convinced that there is any particular benefit in using it even if the rest of the application is being designed using Rational Rose, but if it is a company standard go ahead and try. I am not particularly happy with the assumption that a class equals a table - it is certainly not a restriction that one should be rigid about.

    I am very interested in hearing from anyone who can tell me some of the advantages of using Rational as a common tool (if any).
    try using google to come up with this document erwin_insider.pdf

  7. #7
    Join Date
    Apr 2004
    Location
    Toronto, Ontario, Canada
    Posts
    4
    Thanks, I'll take a look.

  8. #8
    Join Date
    Apr 2004
    Location
    Toronto, Ontario, Canada
    Posts
    4

    ERwin_insider.pdf

    Well I read it - interesting (except for the errors e.g. fig 37) and I agree that UML has some features not available in IDEFIX notation, but, like another modelling language, Object Role Modelling, what do I do with the differences when it comes to building a database.

    Rational Rose allows one to convert a class diagram to a data model diagram and produce DDL, but the conversion results may need to be modified to take care of actual database implementation requirements.

    Visio has an ORM modelling facility but you can't get DDL until you convert it to an ER diagram and you lose much of the extra information.

    I really want some information on why it would be an advantage to use UML as a modelling language when the end result for me is to produce a well designed working database. One answer might be that since one has to build a class diagram for the developers one might as well use it to define the database - but as I indicated, that approach in practice does not work very well - not all classes are tables, not all tables are part of the class diagram. In any case developers I've worked with often prefer to work with sequence diagrams.

    Finally - what advantage is UML (over ER) when designing Data Warehouses. If I sound negative it is mostly because people tell me of the theoretical advantages, but seem to fade out when it comes to practical advantages.

  9. #9
    Join Date
    Mar 2001
    Location
    Lexington, KY
    Posts
    606
    UML is missing a lot of data management features:
    http://www.dbdebunk.com/page/page/622916.htm

    UML == bad.
    Thanks,

    Matt

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