NXxpcs: discuss at telco

[prjemian]

There was some discussion about @storage_mode and the two different representations of g2. This would be best discussed in a meeting where both members of the XPCS community and the NeXus tech committee are present.

Originally posted by @prjemian in #982 (comment)

[prjemian]

Also, other concerns, were noted in issues:

• NXxpcs: what's the difference between the "entry_identifier" and the "scan_number"? What purpose are they trying to fulfill? #1004
• NXxpcs: On review of the equation for g2, the units are identical in numerator and denominator. The correct unit type for this is NX_DIMENSIONLESS. #1005
• NXxpcs: processed data needs NXprocess group #1006

each of which was resolved in a matching pull request, listed here:

• NXxpcs: clarify use of entry_identifier, entry_identifier_uuid, and scan_number #1188
• change g2 unit type to NX_DIMENSIONLESS #1008
• NXxpcs: add NXprocess group #1009

[prjemian]

XPCS community will request participation in upcoming telco to discuss. Needs to go on agenda for that meeting.

[prjemian]

The doc string should make it clear that either format may be used, but one of them MUST be used.

[prjemian]

It seems the only remaining item to be resolved was the multiple representations of g2 (and twotime). The NXcanSAS specification has a similar representation of Q in either of two forms.

Advice today was that we have nothing to change today, other than the documentation addition above.

[prjemian]

• consider XML union construct in nxdl.xsd

[prjemian]

There was also discussion about this remark:

Any of these values: one_array | data_exchange_keys | other

which comes from:

definitions/contributed_definitions/NXxpcs.nxdl.xml

Lines 158 to 162 in e9f7406

	<enumeration>
	<item value="one_array"/>
	<item value="data_exchange_keys"/>
	<item value="other"/>
	</enumeration>

,

definitions/contributed_definitions/NXxpcs.nxdl.xml

Lines 173 to 177 in e9f7406

	<enumeration>
	<item value="one_array"/>
	<item value="data_exchange_keys"/>
	<item value="other"/>
	</enumeration>

, and several additional places in the NXDL.