[CESG] CCSDS 301.0-B-4 propsed pink sheet (Time Code B) / Backward compatibility?

Thu Aug 4 08:52:52 UTC 2016

Hi Erik,

I believe your proposed change is not needed as it is already covered by 
the standard, in particular by clause 3.5.1.3.c. In fact, there it is 
clearly stated that:
[...] time subsets [...] may be abbreviated to the span of interest by 
deleting the unneeded subfields, either on the left or on the right. This 
implies that one can delete the "d→d" subfield
When subfields are deleted on the RIGHT, the separators that had delimited 
the deleted subfields are dropped. This implies that one can delete the 
decimal dot

For the decimal dot I believe the current solution is OK. Robust 
implementations should parse the time code string until they find the "Z". 
If they find a "." before, then the time has decimal fraction of second.

On the other hand, clause 3.5.1.3.c provides full flexibility to eliminate 
any subfield. This seems to me not clean and not in the spirit of 
standardisation as it results in the proliferation of different time 
formats, which require specific ICDs to make them unambiguous.

Regards,

__Mario

From:   "Shames, Peter M (312B)" <peter.m.shames at jpl.nasa.gov>
To:     "Barkley, Erik J (3970)" <erik.j.barkley at jpl.nasa.gov>
Cc:     "CESG -- CCSDS-Engineering Steering 
Group\(cesg at mailman.ccsds.org\)\(cesg at mailman.ccsds.org\)" 
<cesg at mailman.ccsds.org>
Date:   04/08/2016 05:04
Subject:        Re: [CESG] CCSDS 301.0-B-4 propsed pink sheet (Time Code 
B) / Backward compatibility?
Sent by:        "CESG" <cesg-bounces at mailman.ccsds.org>

I agree.  I think clause 3.5.1.3.c covers this case (and even the hh:mm 
case).  I just hope that implementations are robust enough to handle it 
correctly.

Peter 

Sent from Peter's iPhone 6 

Everything should be made as simple as possible, 
but not simpler. 

~Albert Einstein

On Aug 3, 2016, at 6:34 PM, Barkley, Erik J (3970) <
erik.j.barkley at jpl.nasa.gov> wrote:

Gippo,

I too noted that it might be possible to interpret 3.5.1.3 as already 
allowing removal of the decimal fraction/sub-second. 

CESG members,

What is your taking/reading on this?  Does this already allow fractional 
seconds to be optional?  If not, why not? 

Best regards,
-Erik

From: Gian.Paolo.Calzolari at esa.int [mailto:Gian.Paolo.Calzolari at esa.int] 
Sent: Monday, July 25, 2016 2:26 AM
To: Barkley, Erik J (3970) <erik.j.barkley at jpl.nasa.gov>
Cc: CESG -- CCSDS-Engineering Steering Group (cesg at mailman.ccsds.org) (
cesg at mailman.ccsds.org) <cesg at mailman.ccsds.org>
Subject: Re: [CESG] CCSDS 301.0-B-4 propsed pink sheet (Time Code B) / 
Backward compatibility?

Erik, 
        from a purist point of view I think that it would be incorrect 
stating that the change is backward compatible as a former implementation 
would expect to find always the "Decimal fraction of second" and would 
most likely crashes when that field is absent. 
Conversely a constant setting to 0 when not used would be fully backward 
compatible. 

However it is also true that despite section 3.5.1.2 "ASCII TIME CODE B, 
Year/Day of Year Calendar Variation" defines only one optional field (i.e. 
the time code terminator) section 3.5.1.3 "SUBSETS OF THE COMPLETE TIME 
CODES" basically allows many fields to be optional so I wonder whether it 
would be more correct working on section  3.5.1.3 instead of adding the 
optional field in section  3.5.1.2. 
In other words, the part of 3.5.1.3 clause (c) stating that the code "may 
be abbreviated to the span of interest by deleting the unneeded subfields" 
does already allow removing the Decimal fraction of second subfield? 

My cent....... 

Gian Paolo 

PS It looks to me that the sentence "the need to accommodate the upcoming 
century rollover in only 11 years" was somehow wrong in 2010 as it is now  
:o) 

From:        "Barkley, Erik J (3970)" <erik.j.barkley at jpl.nasa.gov> 
To:        "CESG -- CCSDS-Engineering Steering Group (
cesg at mailman.ccsds.org) (cesg at mailman.ccsds.org)" <cesg at mailman.ccsds.org> 

Date:        22/07/2016 01:44 
Subject:        [CESG] CCSDS 301.0-B-4 propsed pink sheet (Time Code B) 
Sent by:        "CESG" <cesg-bounces at mailman.ccsds.org> 

CESG Colleagues, 

Attached is the proposed pink sheet for Time Code B which makes the time 
code more suitable for such applications as publishing a standardized 
schedule of services for which mandatory fractional seconds is 
meaningless.  (By the way does anyone know what the original rationale was 
for requiring, at a minimum, 1/10 of second time statements?)  The 
proposed change is the addition of “(optional)” which is in keeping with 
the method by which optional is designated for the “Z” character in the 
recommendation.  I believe the “.” subfield separator disappears of by 
application of 3.5.1.3 clause (c).    If this change is made to Time Code 
B, we likely should apply it to Time Code A.   

Best regards, 
-Erik 

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