Re: The wisdom of the object mentors (Was: Searching OO Associations with RDBMS Persistence Models)

From: J M Davitt <jdavitt_at_aeneas.net>
Date: Thu, 01 Jun 2006 01:48:55 GMT
Message-ID: <bIrfg.52074$P2.29_at_tornado.ohiordc.rr.com>


Robert Martin wrote:
> On 2006-05-31 10:53:23 -0500, Bob Badour <bbadour_at_pei.sympatico.ca> said:
>

>> Robert Martin wrote:
>> The decision to use SQL or Relational technology is NOT at the
>>
>>> core of the system.  But the structure of the data IS.  That 
>>> structure can, and should, be decided in a technolgy agnostic way for 
>>> as long as possible.
>>
>>
>> And this is why I say that what you write is such ignorant tripe.

>
>
> Ah, back to the ad-hominems.
>
>> A logical data model provides the structure, manipulation and 
>> integrity for a formal system. A good logical data model imposes no 
>> particular structure on the data as a whole while it does provide a 
>> structure in which to represent data. In fact, the structure of the 
>> data itself depends largely on one's point of view. One drastically 
>> alters the appearance of any graph by starting at a different location 
>> and traversing the edges in different directions.

>
>
> I'm with you so far.
>
>>
>> As a logical data model, the relational model works very well

>
>
> Surely.
>
>>  while the available alternatives work very, very poorly by comparison.

>
>
> Certainly there are application domains where I would not hesitate to
> use RDBs. There are also application domains where I would not think of
> using them at all. So for some application domains RDSBs work very
> poorly, and other mechanisms work much better.
>
>> Even if one is forced to use a non-relational product, one would have 
>> to be a complete ignorant fool not to analyse the design relationally. 
>> It is, after all, the only formalism we have for data that is, itself, 
>> predicate logic and that treats all data symmetrically.

>
>
> I disagree. There are many data representations that can be useful and
> fruitful. The oft touted formalism of RDBs is fine; but does not
> preclude other mechanisms. For example, simple data structure
> representations are sometimes much more convenient and efficient than an
> RDB. As another example, consider your laptop. A lot of data is
> organized on that laptop using a directory and file structure rather
> than an RDB. This seems to work quite well as a general purpose
> organizing principle. There is no hue and cry for our filesystems to
> suddenly be RDBs.
>
>>
>> As the only available symmetric data model, it is the only logical 
>> data model that even begins to allow one to consider data in a 
>> technology agnostic way.

>
>
> Again I disagree. I agree that RDBs DO allow a technology
> independence. However, they are not the only means to achieve this.
> Again, consider filesystems. I am currently typing this on a macintosh
> that has a window open with MS windows running inside. The Windows
> filesystem can see into the mac file system with no trouble. Indeed,
> the virtual windows OS can see accross the network to another windows
> machine and see the files there. Filesystems seem to be quite
> technology agnostic.

Using file systems to make your point is a very poor choice. Take a file, copy it over there. Identical content, different paths. Which is "real?" Which is a copy? Which one should I modify if I want my changes to persist? How do Suzie and Bob and Joey and Ron know which is the one I scribbled in? What's keeping track of that? A file system? No way!

These, and other, questions become de minimis in the relational model.

>>
>> Given that, what you wrote above was self-contradictory while 
>> suggesting you live in some fantasy world where data may only ever 
>> appear in a single graph.

>
>
> You might be surprised at the world I live in.
>
>
Received on Thu Jun 01 2006 - 03:48:55 CEST

Original text of this message