The ORM Foundation

Refering to Matt's points: Sure subtyping and subset/equality constraint are not the same, but if you objectify two connected predicates, you get subtypes. To connect more then two predicates, the arrows would need to split - I already do this for subtyping to avoid parallel lines (first model in the third row). I am not sure about ...

Models get hard to read if you use subset constraints and equality constraints between roles. Sure there are good reasons to use them, but I found that you do not need special symbols and line styles to depict them. Suptyping and subset constraints are the same concept - one for object types, the other for (combinations of) roles. So why not just ...

[quote user="Terry Halpin"]One problem with IRIs is that the same element may be assigned different IRIs by different users, weakening the notion of a preferred identifier[/quote] That is not an issue if IRIs but of usage of IRIs. It is an explicit feature: Everyone is allowed to state anything about anything on the Semantic Web. If ...

Hi Matthew! Thanks for the detailed feedback! I changed the picture to show the preferred uniqueness constraints and the implied parts of the model. I think there is no standard syntax for implied model parts so I implemented them in grey -- better suggestions are welcome. I thought about using italics for implied types but there can also be ...

ORM2 provides "reference modes" that can be used to hide value types. This way you can talk about entities as if they were values. I tried to explain reference modes in a picture.

Reference modes are not described very deeply in Haplin and Morgan (2008) - there is an introduction to the different reference mode kinds (popular, general, and unit based) at page 85 and page 98, but the ORM syntax cheatsheet does not distinguish. I tried to unwrap the semantics of reference modes in a picture (source): I also added a ...

I moved the project to github where you can better follow its development, add feature requests and bug reports etc. Placing the nodes must be done manually but TikZ helps you with some dynamic layout capabilities. It also supports changing the default margins and other parts of the layout. It's not clear to me which part of the diagram is too ...

TikZ is a fully programmable language to create graphics which makes it both powerful and complex. Maybe tkz-orm can better be compared to Visio ORM Stencils because its purpose is only to create ORM2 diagrams and not all of the features that NORMA provides. I created the tool to embed ORM2 diagrams in my LaTeX documents - I don't have a Visio ...

I have released tkz-orm, a LaTeX package to draw ORM2 diagrams by using the TikZ package. See here for an example and here for the documentation. You need the CVS version of TikZ in order to use tkz-orm (a build is available at texamples). The full package is free software / open source, so you don't need any commercial softwarelike Visual ...

Dear Clifford and all of you, The discussion touched several interesting points and helped to get a deeper understanding of ORM. Especially some more philosophical points that Ken mentioned are very interesting. To start, I will focus on more technical issues. My current understanding is that the .orm file format as exported by NORMA, which is an ...