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Duplicate Data-Items after reegenering and generate CDM

Hi,

I have done a reverse engenering of an existing data-base, then I generate a conceptual model. My issue is that, when I use a same Field (eg: Amount) in different tables, This will generate multple data-items in CDM. How can I avoid this or correct it in order to be able to build a Data Dictionary?

By advance thanks for your reply.

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3 Answers

  • Jan 20, 2017 at 03:20 PM

    The simple answer is that they are not the same Data Item :).

    For example, assume that the following three entities all have an attribute called "Balance Amount":

    • Customer Lending Account
    • General Ledger Account
    • Cashier Station

    Those three attributes may have different data types, but the main point is that they have completely different meanings. When generating your CDM, PowerDesigner is not going to assume that these three attributes are the same data item. Here's the definition of Data Item from the Help:

    "A data item is an elementary piece of information, which represents a fact or a definition in an information system, and which may or may not have any eventual existence as a modeled object."

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  • Jan 20, 2017 at 06:15 PM

    When you generate the CDM from the PDM, you need to change the CDM Model Options. By default, the 'Allow Reuse' option for Data Item' is not selected. You can reference the PD Help for CDM Model Options for more specifics.

    To solve your question:

    • Open PDM
    • Select Tools - > Generate Conceptual Data Model
    • In the CDM Generation Options window, click Configure Model Options
    • In Model Options window, select the Allow reuse option for the Data Item
    • Click OK
    • Click OK to generate the CDM
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  • Jan 21, 2017 at 05:58 PM

    Hello Patrick, sorry I forgot to mention the option to allow data items to be reused. It's a useful feature, but be careful how you use it. If you have one Data Item called "Amount", referenced by 50 attributes, they will all have the same description, data type, etc. Is that what you really want?

    Say you do create a single Data Item called "Amount", then decide that it would be more meaningful to have separate Data Items for each instance, that would be a lot of work. For example, you might create the following Data Items:

    • Lending Account Current Balance Amount
    • Lending Account Day Start Balance Amount
    • General Ledger Account Current Balance Amount
    • General Ledger Account Day Start Balance Amount
    • Cashier Station Float Day Start Balance Amount
    • Cashier Station Float Day Current Balance Amount

    In my not-so-humble opinion, there is no value to a Data Item called "Amount" - none of the naming standards I've ever used would allow an attribute or column name to consist of the data class (such as "Amount", "Number" or "Text") and nothing else. If you want an object that represents all Amounts, use one or more Domains, such as:

    • Account Balance Amount
    • Transaction Amount
    • Amount (12,4)
    • Amount (8,2)

    Possible strategies for Domains are covered in one of my PowerDesigner training courses :)

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