Re: RM and abstract syntax trees

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Tue, 30 Oct 2007 15:13:16 -0300
Message-ID: <4727743d$0$14874$9a566e8b@news.aliant.net>

paul c wrote:

> David BL wrote:
>

>> On Oct 30, 6:29 pm, "Roy Hann" <specia..._at_processed.almost.meat>
>> wrote:
>>
>>> "David BL" <davi..._at_iinet.net.au> wrote in message
>>>
>>> news:1193713604.283167.146850_at_e34g2000pro.googlegroups.com...
>>>
>>>> In the following I compare different techniques for representing an
>>>> Abstract Syntax Tree (AST), concluding that RM is poorly suited.
>>>
>>> [snip]
>>>
>>>> I anticipate that this rule of thumb provides a useful insight on that
>>>> rather vague notion of "semi-structured data".  ie it explains exactly
>>>> when and why there is data that is not suitable for direct
>>>> representation in RM.
>>>
>>> Education triumphs over learning once again.
>>>
>>> Roy
>>
>> Please say what you disagree with.  I can take it.

>
> Okay, from your original post:
>
> "So RM is forced
> to expose the equivalent of pointers directly in the representation.
> Furthermore, the RM has no mechanism for hiding these pointers or
> giving the user an interface that promotes the idea that a node
> logically represents a value."
>
> Where does RM ever mention pointers? Eg., What are the pointer
> operations that RM supports?
>
> (ps: I don't agree that RM can't represent nested lists but I would
> agree that it's not much fun to manipulate them, I wish Codd had said
> more about nested relations as I have a feeling he spent some time
> considering them.)

It seems he considered them unecessary in the sense one can always normalize the data to obviate the need for them. Received on Tue Oct 30 2007 - 13:13:16 CDT