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  • Re: Relational Mapping Algorithm - is it OK?

     Thanks for your further response, Nicola.   Linking Enrollment to LabSessionNr is correct, as Enrollment already contains the relevant Course. Of course, many lab sessions may have the same number, but this is not a problem.   In modeling, one may often choose between using a derivation rule or subset constraint.    As ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Fri, Nov 2 2018
  • Re: Relational Mapping Algorithm - is it OK?

     Hi Nicola Please see the attached pdf file for further thoughts on your example and its relational mapping in NORMA. I think this shows a more realistic way to model the example that avoids the mapping issue that you raised. Cheers Terry
    Posted to ORM Techniques (Forum) by Terry Halpin on Thu, Nov 1 2018
  • Re: Relational Mapping Algorithm - is it OK?

     Hi Nicola    I get a different relational mapping result when I use NORMA. Please see the attached pdf file for some discussion on this issue. Cheers Terry 
    Posted to ORM Techniques (Forum) by Terry Halpin on Sun, Oct 28 2018
  • Re: Constraints on Constraints?

     To meet your objective in ORM, you could derive a relationship that is the union of the two other relationships, then subset from the given relationship to the derived one. For example, consider the binary relationships with predicates R, S and T from A to B. Now create a derived predicate U from A to B. so that forall x, y [xUy if (xRy v ...
    Posted to Open Discussion & Feature Requests (Forum) by Terry Halpin on Wed, Dec 20 2017
  • Re: NORMA Lab 4

     I assume you mean slide 25 of Lab 4. The square brackets are around role names. NORMA automatically adds the square brackets when you enter the role name.  To add a role name, right-click the role box and enter the name in the Name property. Cheers Terry 
    Posted to Discuss documentation (Forum) by Terry Halpin on Sun, Jun 4 2017
  • Re: Irreflexive Ring vs. Value Comparison constraint -- Are they equivalent?

     Hi Gordon Yes, an irreflexive ring constraint is equivalent to a value-comparison constraint with the inequality operator. E.g. a simple irreflexive constraint on a binary predicate R formalizes as  forall x not xRx, and a corresponding value-inequality constraint formalizes as  forall x, y (xRy -> ~x=y). It's easy to prove ...
    Posted to Technical support (Forum) by Terry Halpin on Thu, Apr 20 2017
  • Re: Latest version of Tutorials

     Hi Jeff  Which file do you mean by "Tutorial 1"?  If you mean NORMA Lab 1 (which I updated on 2016 August 31), then slides 22-24 don't have any verbalization on them. Please clarify.  Cheers Terry   
    Posted to Discuss documentation (Forum) by Terry Halpin on Thu, Apr 6 2017
  • Re: Using ORM to Model User-defined DataTypes

     ORM recognizes three kinds of object types: entity type (e.g. Country); domain value type (e.g. CountryCode) often shortened to "value type", and data type (e.g. string). Value types carry more semantics than data types (e.g. the CountryCodes 'CH'and 'DE' are based on Latin and German ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Sun, Oct 23 2016
  • Re: Thank you

     Dear Berhanu  Congratulations on earning your master's degree!  And thank you for your kind words of appreciation for my support. It was a pleasure discussing ORM with you. Kind regards Terry 
    Posted to Contributed Models (Forum) by Terry Halpin on Mon, Mar 28 2016
  • Re: Relational View - different display formats?

    Hi Marc While we do support those other display options at the conceptual level, their use at the relational level seems inappropriate. Perhaps you could describe the specific relational notation(s) you would like us to support. Cheers Terry 
    Posted to Open Discussion & Feature Requests (Forum) by Terry Halpin on Sat, Feb 6 2016
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