The ORM Foundation

Get the facts!

Search

Page 2 of 3 (22 items) < Previous 1 2 3 Next >
  • ORM models and OO

    Hi, In my mind, the conceptual model in ORM is modelling the &quot;problem space&quot;, not the &quot;solution space&quot;.&nbsp; Because ORM is aimed at being able to generate a (pure, i.e. 5NF?) relational database solution, this means that there are certain OO constructs, such as mutually exclusive supertypes, that are not ...
    Posted to ORM Techniques (Forum) by PeterC on Mon, Apr 6 2009
  • Re: Using data-type for rule modeling

    Hi Ken,Sorry if this is now off-topic, but Ill try to clarify statements that youve found confusing because if you have trouble with them, then there may be many other readers also scratching their heads.I said: even if there is a one to one mapping between the two. and you said: I don&#39;t see how there can be one-to-one mapping between ...
    Posted to ORM Techniques (Forum) by PeterC on Sat, Apr 4 2009
  • Re: What are the "must have" features for an ORM tool?

    Hi Brian, &nbsp; I thought there would be more in this thread than this. &nbsp; In 2003 I discovered ORM and used Visiomodeler to attempt to create a model and create the database for a large project (for which I was the data architect).&nbsp; After producing 45 A3 pages of conceptual model (and ~600 A4 pages of generated reports), it was ...
    Posted to Other Tools (Forum) by PeterC on Fri, Apr 3 2009
  • Re: Using data-type for rule modeling

    Hi Ken, You have expounded well that which I did not have the skill to do. You said: on their own, words do not have any meaning. Words only have meaning within a context. &nbsp;I could not agree with you more. What I wanted to achieve in the first example (permissible values seven, pi, and e) was to demonstrate that &lt;context in a ...
    Posted to ORM Techniques (Forum) by PeterC on Fri, Apr 3 2009
  • Re: Using data-type for rule modeling

    Hi Ken, Those are very interesting examples indeed. In your post, you made a statement that got me thinking.&nbsp; The following reflects some of my thoughts and understanding of ORM and the issue raised in this thread. In your post, you said: Regarding data types, I don&#39;t see how we can escape from the notion of using data types to ...
    Posted to ORM Techniques (Forum) by PeterC on Mon, Mar 30 2009
  • Re: Disjunctive Reference Schemes

    Thanks, Ken.&nbsp; That was a good explanation. (After I hit the Post button I realised that I had stuffed up my wording - which means I really shouldn&#39;t Post when I&#39;m tired.)&nbsp; On the occasion I have had nulls in keys, they were always composite keys, and were mainly used to hold the results of queries with outer joins, rather than ...
    Posted to User experience (Forum) by PeterC on Sat, Mar 28 2009
  • Re: Disjunctive Reference Schemes

    Hi Andy, You don&#39;t need a second subset constraint because &#39;has first&#39; is mandatory. I&#39;m really more interested in your statement that Primary Key columns should never contain NULLs.&nbsp; Why?&nbsp; I&#39;m happy to create tables with NULLs in PKs and FKs if it achieves what I need.&nbsp; (Not that it happens often, mind.)&nbsp; ...
    Posted to User experience (Forum) by PeterC on Sat, Mar 28 2009
  • Re: Using data-type for rule modeling

    Hi Brian, I&#39;m surprised there hasn&#39;t been more discussion on your approach.&nbsp;&nbsp;I&#39;ll give my tuppence worth since you asked for others&#39; views... The rule that Amount must be a positive value is not read from the diagram model, and to me this is a shortcoming in the model - I too do not like the idea of leaving the ...
    Posted to ORM Techniques (Forum) by PeterC on Thu, Mar 26 2009
  • Re: Disjunctive Reference Schemes

    &nbsp;An observation.... While perusing this thread, I noticed that the solution proposed by Ken does not contain the same information as that in the opening post by Andy.&nbsp; In Andy&#39;s, I know the full name of the member, but in Ken&#39;s I do not know in what order the given name&#39;s occur.&nbsp; (Or does the frequency constraint ...
    Posted to User experience (Forum) by PeterC on Thu, Mar 26 2009
  • Re: Mutually exclusive supertypes

    Thanks.&nbsp; So in my example model (not my real project which is way more complex), as a work around, I change &#39;Bat is a Flying_critter&#39; to &#39;Bat has a Capacity_to_fly&#39;.&nbsp; That is, I change the relationship from hierarchy/inheritance to component.&nbsp; Which means I cannot define an EntityType that represents the set of ...
    Posted to Open Discussion & Feature Requests (Forum) by PeterC on Thu, Mar 26 2009
Page 2 of 3 (22 items) < Previous 1 2 3 Next >
© 2008-2020 The ORM Foundation: A UK not-for-profit organisation -------------- Terms of Service