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  • Re: How to model maximum rental period for a year

    &nbsp;As a follow-up to my previous response, the term &quot;Period&quot; has multiple dictionary meanings. It can mean simply a duration in time (e.g. 7 days), or instead an anchored duration in time with a specified start and end time (e.g. the period from 2015 Sep 11 to 2015 Sep 18). If your model needs both concepts, I suggest you use Duration ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Thu, Sep 17 2015
  • Re: How to model maximum rental period for a year

    &nbsp;Hi Jacob Of your three solutions, the one with Period(days) is preferable as that best captures the semantics. However, you should declare the reference mode to be unit-based -- it will then appear with an appended colon thus: Period(days:). As a minor change, I would rephrase the predicate reading to make it infix, e.g. Year(CE) limits ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Thu, Sep 17 2015
  • Re: Simple exclusion constraint and Exclusive or constraint

    &nbsp;Your wrote and reviewed examples sounds like two binary fact types: Person wrote Book; Person reviewed Book. There would be a pair-exclusion constraint between these fact types, so no person can write and review the same book. In this case, each argument of the exclusion constraint is a (Person, Book) role pair. &nbsp; An exclusive-or ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Tue, Sep 1 2015
  • Re: Simple exclusion constraint and Exclusive or constraint

    &nbsp;As a follow-up to Andy&#39;s excellent explanation, the characterization of an exclusive-or constraint in &quot;However, in Exclusive-or constraint, Entity A can use Role1 or Role2,but not both. I cant see the difference here.&quot; should have used &quot;must&quot; instead of &quot;can&quot;. &nbsp; An exclusive-or constraint combines an ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Tue, Sep 1 2015
  • Re: ORM and FCIOM

    Hi Berhanu Regarding the 1996 paper by Weber and Zhang, I disagree with some of the claims made in that paper, and not see &quot;construct overload&quot; as a problem for NIAM or ORM. It is not uncommon for people to argue that NIAM and ORM are too expressive in their graphical notations, but I believe it is very convenient for modelers to ...
    Posted to Technical support (Forum) by Terry Halpin on Mon, May 25 2015
  • Re: Modeling that the newest bid is higher than any existing bid

    &nbsp;Hi Matt Yes,&nbsp;www.factbasedmodeling.org&nbsp;is the website for the FBM Working Group. To get access to the metamodel, I suggest you join the working group, which is chaired by Serge Valera (see the membership page). &nbsp;Cheers Terry&nbsp;
    Posted to ORM Techniques (Forum) by Terry Halpin on Fri, May 22 2015
  • Re: Modeling that the newest bid is higher than any existing bid

    Hi Jacob The FBM metamodel contains numerous examples of verbalizations of derivation rules, but we have not yet published the dynamic rule syntax. Cheers Terry.
    Posted to ORM Techniques (Forum) by Terry Halpin on Wed, May 20 2015
  • Re: Modeling that the newest bid is higher than any existing bid

    &nbsp;Hi Jacob &nbsp; As I indicated earlier, your problem can be handled more efficiently using a dynamic rule. We have specified extensions to ORMs rule syntax to support such rules, which can refer directly to states immediately previous to a transaction (e.g. the previous bid), but have not yet implemented this rule syntax in NORMA, so ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Wed, May 20 2015
  • Re: Modeling that the newest bid is higher than any existing bid

    &nbsp;Hi Jacob &nbsp; First let me correct an obvious omission from my previous rule, which should have read as follows: * Bid1 is highest for Advertisement if and only if &nbsp; &nbsp; &nbsp; that Bid1 is for that Advertisement and offers some Price1 &nbsp; &nbsp; &nbsp; and no Bid2 &lt;&gt; Bid1 and is for that Advertisement ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Fri, May 8 2015
  • Re: Modeling that the newest bid is higher than any existing bid

    &nbsp;Hi Jacob &nbsp; Assume the ORM schema contains the following fact types, each of which is mandatory and many-to-one. Bid(.Nr) is for Advertisement(.Nr). Bid is by Consumer(.Nr). Bid offers Price(USD:). Bid is made on Date(ymd). &nbsp;Now you may define the derived fact type &quot;Bid is highest for Advertisement&quot; (optional, ...
    Posted to ORM Techniques (Forum) by Terry Halpin on Tue, May 5 2015
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