W3C home > Mailing lists > Public > public-owl-wg@w3.org > July 2008

Re: A possible structure of the datatype system for OWL 2 (related to ISSUE-126)

From: Rob Shearer <rob.shearer@comlab.ox.ac.uk>
Date: Thu, 10 Jul 2008 11:08:44 +0100
Cc: "Boris Motik" <boris.motik@comlab.ox.ac.uk>, "'OWL Working Group WG'" <public-owl-wg@w3.org>
Message-Id: <7244BCAC-DC65-4781-9D8B-494B5E13A809@comlab.ox.ac.uk>
To: Alan Ruttenberg <alanruttenberg@gmail.com>
>>> On today's hardware, I would set this to be 64 bit integers or even
>>> 128 bit integers, and double precision float. Some machine's don't
>>> really have single float hardware, instead rounding from double  
>>> float.
>>>
>>
>> I don't mind going up to 64 bit. 128 might be a bit too much (at  
>> least in Java -- a language in which many reasoners are implemented
>> you don't have this).
>
> http://java.sun.com/j2se/1.4.2/docs/api/java/math/BigInteger.html
> Need only invoke code based on it in case of an overflow exception.

This line of argument worries me---the fact that there are easy-to-use  
classes in Java doesn't seem like sufficient reason to extend the spec  
to features that I expect will be important to very very few users.

I have encountered users who could make use of 64-bit integers  
(although not many). The only users I've ever encountered (or even  
heard about) who claim the need larger integers fall into two groups:

1. Mathematicians/cryptographers for whom 128-bit number aren't big  
enough either; i.e. they need arbitrarily-sized integers.
2. Programmers who use "integer" to mean "bit string". 128-bit bit- 
strings are very useful, but they don't require "integer" semantics  
and thus are probably better served by a "binary data" type.

I'd still argue that we should only require implementors to support 32- 
bit constants since that covers all common usage. I'd say that 128-bit  
integers are completely and utterly unreasonable, and I almost  
certainly wouldn't implement them (unless I also implemented arbitrary- 
precision integers).

I admit I probably would implement 64-bit integers, but still think  
the spec is better off not requiring them.

-rob



Received on Thursday, 10 July 2008 10:13:02 UTC

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