Subject: Re: Lets Standardize Time Representation Formats!!!: WAS Re: New TSTTime definition

From: "Aram Perez" <[email-masked]>
Date: Tue, 03 Aug 1999 12:25:26 -0700

Tony Bartoletti wrote:

> At 11:20 AM 8/3/99 -0700, Aram Perez wrote:
> 
>>I personally prefer a
>>numerator/denominator approach such as (please excuse my ASN.1):
>>
>>    Seconds ::= SEQUENCE {
>>        numerator INTEGER,
>>        denominator INTEGER OPTIONAL DEFAULT 100
>>    }
>>
>
> For compactness, (idea courtesy of Denis Pinkas earlier post) why not
> specify the denominator as a power of 2? (bit-shifts are fast.)

Sure, just make the default 2.

>
> I can believe Todd's argument that high precisions/resolutions may
> be/become important, but I wonder the utility of, say, denom = 119.

I would wonder also if someone used a denominator of 119. What I see is a
trade-off between compactness and arbitrary precision. I'm just proposing a
scheme where you can be as precise (or unprecise) as you want to be. In the
long run, I think different "industries" would adopt different "standard"
denominators.

>
> But I am a bit confused by the "numerator/denominator" notation.
>
> E.g.:  If the denominator were 1000 (I like milliseconds;) then
> would I need to represent 57.000 seconds as 57000/1000 ?

That is correct. Actually, a better representation would be:

    Seconds ::= SEQUENCE {
        whole-secs INTEGER,
        fraction-numerator INTEGER,
        fraction-denominator INTEGER DEFAULT 100 -- Correct ASN.1
                                        -- Thanks to Tom Gindin
    }

Still having fun,
Aram Perez

---

From: Michael McNeil <[email-masked]>
Date: Wed, 04 Aug 1999 09:27:35 -0700

Aram Perez wrote:
>>Aram Perez wrote:

>>For compactness, (idea courtesy of Denis Pinkas earlier post) why
>>not specify the denominator as a power of 2? (bit-shifts are fast.)
>

If we're specifying a denominator which is a power of 2, how about
2^^32 (the natural denominator for fractional quantities within a
32-bit binary cell), or 4,294,967,296.  This is the format used by
the fractional portion of the time in NTP (Network Time Protocol).
(In this quantity of time, light will travel about 3 inches.)

>>I would wonder also if someone used a denominator of 119. What I
>see is a trade-off between compactness and arbitrary precision. I'm
>just proposing a scheme where you can be as precise (or unprecise)
>as you want to be. In the long run, I think different "industries"
>would adopt different "standard" denominators.

Why not just tack on enough bits to satisfy all future expectations?
if 2^^(-32) isn't precise enough for future needs, then I'm prepared
to hear arguments in favor of 2^^(-64).  It's only 64 bits, with a
binary numeric format which is easily handled by today's processors.

Regards,
Michael McNeil

---

From: Tony Bartoletti <[email-masked]>
Date: Wed, 04 Aug 1999 14:02:07 -0700

>(In this quantity of time, light will travel about 3 inches.)
[snip]
>binary numeric format which is easily handled by today's processors.

Good point.  It will probably be awhile before teams of intercellular
nano-probes negotiate contracts amongst themselves ... I think :)

___tony___