Re: WWW/Internet 2009: 2nd CFP until 21 September
Date: Mon, 10 Aug 2009 16:11:55 GMT
Walter Mitty wrote:
> Anyway, I'm interested in whether XML falls under the topic of machine
> representation of the data and is therefore neither compatible nor
> incompatible with a relational view of data.
> Or whether XML is an alternative tro the relational view of data, and
> therefore one that should be compared with the relational view of data with
> regard to benefits and drawbacks.
Here's an excerpt from an article two of the xml originators wrote (http://www.scientificamerican.com/article.cfm?id=xml-and-the-second-genera):
"The nesting rule automatically forces a certain simplicity on every XML document, which takes on the structure known in computer science as a tree. As with a genealogical tree, each graphic and bit of text in the document represents a parent, child or sibling of some other element; relationships are unambiguous. Trees cannot represent every kind of information, but they can represent most kinds that we need computers to understand. Trees, moreover, are extraordinarily convenient for programmers. If your bank statement is in the form of a tree, it is a simple matter to write a bit of software that will reorder the transactions or display just the cleared checks."
Note the third sentence! Basically, they admit that trees are not universally useful.
Another of many amusing sentences in the article is the very first one:
"Give people a few hints, and they can figure out the rest."
My own experience says otherwise!
Codd (1970) offered formal logic as the basis for designing a data language:
"1.5. SOME LINGUISTIC ASPECTS
The adoption of a relational model of data, as described above, permits the development of a universal data sublanguage based on an applied predicate calculus. A firstorder predicate calculus s&ices if the collection of relations is in normal form. Such a language would provide a yardstick of linguistic power for all other proposed data Ianguages, and would itself be a strong candidate for embedding (with appropriate syntactic modification) in a variety of host Ianguages (programming, command- or problemoriented)."
From what I've seen of XML it has no equivalent language. How can people figure out meaning without language?
I think anybody who reads this article critically can easily conclude that nealy every justification it offers in fact damns the lack of universality in XML. It seems the whole XML exercise was prompted by the fact that HTML expresses nothing but punctuation. When it comes to a theory for organizing and manipulating data, XML compared to pretty much any of the RM's, even the mangled SQL attempt, amounts to nothing but punctuation, big deal! A very naive and fractional solution for very narrow problems encountered in HTML. The only comparison I can stretch out of that article is that tags might be compared with relation names, except that no coherent data theory is offered for manipulating them nor any method for coherent organization, eg., avoiding redundancy and contradictions and physical aspects such as position and ordering. That is left for applications to invent in an adhoc way, which is what Codd was arguing against nearly forty years ago. Received on Mon Aug 10 2009 - 18:11:55 CEST