Re: Ideas for World Hierarchy Example

JOG wrote:
> dawn wrote:
>
> > Neo wrote:
> > > > > Marshall: Almost none of the data is encoded in a way a machine can do any useful semantic processing on it.
> > >
> > > > Dawn: when you click on words in a wiki, similar to "clicking" on a foreign key value within a database (an actual instance of a database), you navigate to another node (called a "document", think "record") that is set up as a tree (specified in xhtml, for example) with more foreign key values found by which you can find more documents (records). A wiki is a web. It can be modeled as a digraph with trees on the nodes. This is pretty much the model for many databases that are not RDBMS's by design (e.g. UniData, UniVerse, OpenQM, Revelation, jBASE, D3, Cache', UniVision)
> > >
> > > Would it be fair to say that RMDBs offer a higher degree of
> > > systematicness but less flexibility?
> >
> > With the implementations of each model (intended model, no
> > implementation is perfect), it would be fair to say that there are more
> > constraints built into the dbms in the case of the RDBMS and more
> > flexiibility with the di-graph.
> [snip]
>
> It would be even fairer to say that a di-graph model cannot model n-ary
> relationships,

I don't understand why you say this. Can you give an example? It is easier to implement n:m relationships between "entities" using the data modeling approaches for non-1NF dbms's than for 1NF, right?

> whereas RMDB's can (although they are not the only
> possible n-ary model). And fairer too to say that a binary model is
> necessarily a weak subset of an n-ary model (e.g. hypergraphs).
>
> I cannot understand why with 40 years of research, papers, and
> practical illustrations such as the replacement of navigational
> databases, and now clear failure of the Semantic Web's di-graph data
> model, people are insistent on trying to reinvent flawed graph-based
> systems.

Well, for one, maybe there really is something to be learned from the successes with the di-graph data models. There are even more years of history we can look to for that. It might be the case that there are both bigger failures and bigger successes using the model I prefer, where there might be more of a cookbook approach not to fail with the RDBMS tools. But I have worked with both and there is a decided difference, where I know what the clear favorite is for me, even if you have a different preference.

> Its almost as though there is a concious disrespect in some parts of
> the community to the years of effort, hard work and diligence of those
> who preceded us.

I wholeheartedly agree. This was definitely an issue, I think, when Oracle and others came in with the marketing and research in one area (Codd's papers) and was able to get a large backing to discount all prior database implementations as "legacy" and in so flawed as to need replacement. Fortunately over the years, much of what worked in the past as come into the SQL-DBMS tools, but we are still sitting here stuck with 3VL and 1NF in many production systems (with more still being written). If our discipline had been more mature at the time, I would hope this wholesale disregard for what were the industry best practices at the time would not have been disregarded without adequate (or any?) emperical data suggesting they should be.

cheers! --dawn Received on Fri Jan 12 2007 - 19:12:16 CET