W3C home > Mailing lists > Public > www-xml-schema-comments@w3.org > January to March 2001

Wht '<=' ? rather than '<'?

From: Kohsuke KAWAGUCHI <k-kawa@bigfoot.com>
Date: Tue, 13 Feb 2001 15:29:28 -0800
To: www-xml-schema-comments@w3.org
Message-Id: <20010213143415.2477.K-KAWA@bigfoot.com>

Dear XML Schema WG members,


Summary
-------
the order relation of dateTime value is not good. So please think about
it again.



Explanation
-----------
In section 3.2.7.3 of the spec part 2,

The order relation of dateTime value is specified as:

> C.Otherwise, if P contains a time zone and Q does not, compare as follows: 
> 
> P <= Q if P <= (Q with time zone -14) 
> P >= Q if P >= (Q with time zone +14) 
> P <> Q otherwise, that is, if (Q with time zone -14) < P < (Q with time zone +14) 

There is no definition of relation '<' and '>'.
And this is the source of all troubles.

Why define '<=' instead of '<' ?



In the section 2.4.1.2 of the spec, it says

> partial order relations have the following rule: 
> 
> for every pair (a, b) from the value space, either a < b or b < a or
> a = b or a <> b where the symbol <> indicates that an order between the two
> values cannot be determined. 

So to be consistent with this definition of partial order,
the only acceptable definition of '<' is:

|  P<Q  iff P<=Q
|  P>Q  iff P>=Q


which results in (from the definition of '<=')

P < Q  iff   P <= (Q with time zone -14) 



In summary, defining '<=' requires additional reasoning for everyone who
read it, and very confusing. So please change it to define '<' directly.


regards,
----------------------
K.Kawaguchi
E-Mail: k-kawa@bigfoot.com
Received on Tuesday, 13 February 2001 18:29:41 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Sunday, 6 December 2009 18:12:49 GMT