[LC-2168] RE: Support of IEEE float

Hi Uchida-san,

We understand that the IEEE float representation is one of the most frequently
requested changes to the EXI specification. We would like to use this
opportunity to better explain our position on this issue and share with you
the rationale that supports it. As you will find outlined below, the WG had
assessed both its advantages and disadvantages in the context of EXI, as well
as alternative ways to assuage the concerns.

The WG came to believe that the use of IEEE float fits better with the
user-defined datatype representation capability [1] of EXI than is integrated
as an additional mandatory physical representation of character information
items that are typed as xsd:float or xsd:double. There are some aspects of
IEEE float that do not lend natureally themselves to the primary role of
EXI as an efficient exchange format of XML, particularly when EXI is required
to remain intrinsically compatible with existing XML family of standards
written to XML infoset, such as XML signatures. The issues the WG looked at
in particular are, less compactness and less amenability to compression,
as well as rounding issues in serialization (base-2 to base-10) and the cost
of stringification required when used with the typical XML APIs (SAX, DOM, etc.)
which are undeniably predominantly text-based.

However, by saying this, it is not our intention to derogate the value nor
it is to neglect its wide-spread use in diverse range of applications. We do
not intend to dispute the merit IEEE float brings to some applications, and
understand EXI might be seen as the perfect opportunity to see that merit
in a way fitted well to XML technologies. Though the EXI spec calls for a
deliberate assessment when considering the use of user-defined datatype
representation, obviously IEEE is one of such cases that warrant the use
of the facility without any question.

It was not an easy discussion within the WG that led to the position
mentioned above. Some argued EXI is not XML enough, and others contended
EXI as not binary enough. We respected both views to find a difficult
balance and better serve both needs. In a way, we do not see EXI as static,
rather it is a core foundation on which things can be further built to suit
use cases, which will make the use of EXI more perfect. The two notable
points of innovation provided by EXI are user-defined datatype representation,
and the provision that permits the definition of schema binding for other
schema languages.

We therefore encourage you to seek the best way to leverage user-defined
datatype definitions to represent float and double data as IEEE floats.
If you find any suggestions that would make it easier to use IEEE float
through user-defined datatype representation, we would love to hear them.
Such suggestion may well find its way into a collateral documents such as
FAQ or Best Practices.

[1] http://www.w3.org/TR/exi/#datatypeRepresentationMap

-taki


-----Original Message-----
From: public-exi-comments-request@w3.org [mailto:public-exi-comments-request@w3.org] On Behalf Of UCHIDA Hitoshi
Sent: Thursday, November 06, 2008 2:47 AM
To: public-exi-comments@w3.org
Cc: youenn.fablet@crf.canon.fr; fujisawa.jun@canon.co.jp
Subject: [LC-2168] Support of IEEE float


Dear EXI WG,

In 7.1 Built-in EXI Datatype Representations,
what do you think about the addition of IEEE float ?
For examples, it takes more time to decode EXI integer
because it isn't same to int type of general programing languages.

--
Regards,
Hitoshi Uchida
<uchida.hitoshi@canon.co.jp>

Received on Wednesday, 15 April 2009 19:24:08 UTC