Wikidata:Property proposal/International Tables for Crystallography space group number

International Tables for Crystallography space group number[edit]

Originally proposed at Wikidata:Property proposal/Natural science

Done: International Tables for Crystallography space group number (P9733) (Talk and documentation)

Description	The space group number as assigned in International Tables for Crystallography Vol. A
Represents	International Tables for Crystallography (Q54237847)
Data type	String
Domain	item, subclasses of space group (Q899033)
Allowed values	[1-9]\|[1-9][0-9]\|1[0-9]{2}\|2[0-2][0-9]\|230
Example 1	triclinic-pedial (Q13364996) → 1
Example 2	triclinic-pedial (Q104519742) → 2
Example 3	space group (Q15041898) → 230
Source	w:List of space groups
Planned use	all Wikidata items for crystallographic space groups
Number of IDs in source	230
Expected completeness	eventually complete (Q21873974)
Distinct-values constraint	yes
Wikidata project	WikiProject Chemistry (Q8487234)

Motivation[edit]

International Tables for Crystallography (Q54237847) Vol. A has enumerated all 230 crystallographic space groups, assigning each one a number. This numbering is widely used in crystallography (see _space_group_IT_number CIF data item for example). Wikidata already uses these identifiers in items for space groups, although this identifier is mostly used in their labels, descriptions or aliases. I suggest structuring it in an appropriate manner. Ungurinis (talk) 13:27, 28 June 2021 (UTC)[reply]

Notified participants of WikiProject Chemistry

Discussion[edit]

Support Useful standard to link to. ArthurPSmith (talk) 16:52, 28 June 2021 (UTC)[reply]
Support good idea even though there are only few entries (230). --Hannes Röst (talk) 00:52, 30 June 2021 (UTC)[reply]
Support Seems reasonable, but the label is long. Is it possible to shorten it? — The Erinaceous One 🦔 07:32, 7 July 2021 (UTC)[reply]
- @The-erinaceous-one: In crystallography, the book name "International Tables for Crystallography" is usually abbreviated to "ITC" or just "IT", so the label could be changed to "ITC space group number" if such abbreviation does not become too obscure. Ungurinis (talk) 05:58, 11 July 2021 (UTC)[reply]
Comment Why is the datatype string and not number? — The Erinaceous One 🦔 07:33, 7 July 2021 (UTC)[reply]
- A useful constraint on this property is the regexp that ensures values from the range 1 to 230. I am not sure if one can use regexps (or constraint ranges?) for numbers (integers) in WD. If the constraint "1 <= ITC SG number <= 230 && ITC SG number is Integer" can not be specified in a WD property description, then specifying the property type as "string" with constraining regexp is IMHO superior than specifying it as a number with no constraints. Also, though technically the ITC number is an integer, it is actually used as an identifier, more like a string, and not as a number: there is virtually no sense to add ITC space group numbers arithmetically (what does a space group 3+5 mean?) or compare their magnitudes (in what sense the space group 76 (P4₁) is less than the space group 78 (P4₃)?), but it makes sense to concatenate lists of ITC space group numbers, e.g. the "1,2" string lists all triclinic space groups. Thus the proposed property indeed behaves more like a string and not so much like an integer. Pterodaktilis (talk) 09:38, 10 July 2021 (UTC)[reply]
- @The-erinaceous-one: This is my first proposal, so I do not know many of the nuances. On Help:Data type I did not see a proper numeric data type ("quantity" did not seem fit for purpose here for me). I am fine with number data type as long as constraints expressed in the regular expression can be enforced. Ungurinis (talk) 05:58, 11 July 2021 (UTC)[reply]
Strong support This is a very useful property. Space group numbers are assigned by the IUCr, a recognized learned society, documented in their fundamental reference work "The International Tables for Crystallography" (ITC) and are stable. Mathematically, they are well defined and identify a space group as an algebraic group up to isomorphism; inferences from this information are unambiguous. Unlike H-M or Hall symbols, where several symbols can be used for the same space group, the ITC number is distinct and unique for each space group. Pterodaktilis (talk) 09:19, 10 July 2021 (UTC)[reply]