Well-formed vs. valid
Jeffrey E. Sussna
jes at kuantech.com
Mon Feb 22 19:45:16 GMT 1999
You are correct. But strictly typed languages were invented for a reason, even though they can't prevent bugs. Well-formedness just seems too lcd.
From: Tim Bray [mailto:tbray at textuality.com]
Sent: Monday, February 22, 1999 11:21 AM
To: Jeffrey E. Sussna; 'XML-DEV'
Subject: Re: Well-formed vs. valid
At 10:58 AM 2/22/99 -0800, Jeffrey E. Sussna wrote:
>One thing disturbs me, however. Much talk seems to be made about documents
>or document fragments being useful because they are well-formed. I don't
>want something well-formed, I want something "valid". Whether validity is
>determined by reference to a DTD or to a schema of some other kind, I need
>more than just the lowest-level syntactic conformance to the XML spec. I
>need to be able to determine that the XML in question conforms to the
>syntactic and semantic constraints imposed by my application.
I've never seen an application so simple that its syntactic/semantic
constraints could be expressed in a schema, DTD or any other flavor.
That's why every commercial DBMS-based app has zillions of lines of
data validation code that have to be run before you actually use
Having said that, I think that validation is a good thing and
essential in lots of applications, and will become a better thing
once we have a more modern schema facility.
>Furthermore, I don't want to have to rely on implicit knowledge contained
>within a proprietary parser in order to do so.
In my experience, you *always* have to write some application-specific
validation code. -Tim
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