Re: Hierarchical Model and its Relevance in the Relational Model

Op vrijdag 30 januari 2015 12:29:48 UTC+1 schreef Derek Asirvadem:
>
> ==== Task: JKL & JH ====
>
> So here is a small task for you that I think will demonstrate many of the issues that we are dealing with in this thread. Given your demonstrated skill in the SQLite link and the RM (forget the "rm" of the mathematicians), I think this would take 30 mins or less.
>
> Produce a data model for a set of tables that is fully compliant with the RM, ie, completely Relational, for the storage of data pertaining to:
> - Countries (Name, FullName, FederationDate, ExpiredDate)
> - State/Province/Territory (Name, FullName, Type)
> - County (Name, Type)
> - Town/Township/Metropolis (Name, Type)
> - Suburb (StreetName(FK), StreetType(FK) )
>
> - StreetName (PK: StreetName (CHAR(50) )
> - StreetType (PK: StreetType (CHAR(3), Name)
>
> For all except the last two, the keys have been left out, the exercise is to determine and decide the keys. Everyone knows that there are ISO or ANSI codes for identifiers, for some of them, just choose good keys from that. Whatever you find as identifiers from a recognised standards body (eg. US ANSI County Codes) is deemed part of the "data".

Usually it's me who's handing out home work. :-) Would you mind if I decline for the reason that it is not my position that at the conceptual level hierarchically nested data is a bad idea in a DBMS or "does not naturally exist"? In fact, I've defended in the past in this newsgroup the position (and still do) that the graph-based models such as (F)ORM data models are actually in that respect superior to the Relational Model, even the nested one.

So please don't confuse my position what James' position. We are almost diametrically opposed on all issues.

• Jan Hidders