The term foaf:focus does not exist yet.
It is likely to be added, and to serve the role of the previously proposed 'foaf:it' or 'foaf:isAbout' proposed properties.
See also SKOS Issue list
SKOS concepts are a level of indirection from the things they're about; their creation dates and creators relate to their nature as information artifacts. So for example, we can have a SKOS concept standing for Bill Gates, and an RDF description of "Bill himself".
<skos:Concept> <skos:prefLabel>Bill Gates</skos:prefLabel> <foaf:focus> <foaf:Person> <foaf:name>Bill Gates</foaf:name> </foaf:focus> </foaf:apropos> </skos:Concept>
Or in Turtle, switching from a personal to a geographic example:
<http://id.loc.gov/authorities/sj96005405#concept> a skos:Concept ; skos:prefLabel "Eiffel Tower (Paris, France)"@en ; skos:altLabel "Tour Eiffel (Paris, France)"@fr ; skos:inScheme <http://id.loc.gov/authorities#conceptScheme>, <http://id.loc.gov/authorities#topicalTerms> ; dct:created "1996-05-08T00:00:00-04:00"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
... to which we might add:
<http://id.loc.gov/authorities/sj96005405#concept> foaf:focus <http://rdf.freebase.com/ns/en.eiffel_tower> . <http://rdf.freebase.com/ns/en.eiffel_tower> a <http://rdf.freebase.com/ns/travel.tourist_attraction> .
This crosses us over from the bibliographic and cataloguing facts associated with LCSH's conceptualization of the Eiffel Tower, to worldly facts and claims about the tower itself. By naming this link ("foaf:focus") we can use such associations to find bibliographic artifacts via arbitrary properties of the thing they're about. For example, the nationality or birthplace of engineers, designers, managers etc.
From #talis IRC
14:48 danbri: ldodds, re 'focus' as a property name (not it/apropos/isAbout) ... actually i like it for another reason: 14:49 danbri: sometimes there are a cluster of skos concepts which have a common focus but in thesaurus you get diferent aspects 14:49 danbri: shakespeare - youth 14:49 danbri: shakespeare - as englishman 14:49 danbri: shakespeare - rumours 14:49 danbri: i think the 'it' relation in each case most usefully points to the core thing of interest, ie. the person 14:50 danbri: ... ie the common focus of all those aspects which can be independently talked about in skos 14:50 danbri: whereas RDF class/property model is more thing-centric 15:27 ldodds: danbri: nice 15:27 ldodds: just emailing the list now 15:28 danbri: thanks!
The idea of this property dates to SWAD-Europe-era SKOS discussions between DanBri and Alistair Miles (skos:it / skos:as). However the SKOS WG didn't standardise anything, and so we're including it in FOAF since FOAF has a few other topic-related properties already.
Naming discussion (danbri/ldodds)
12:21 danbri: is 'apropos' too obscure as a property name? 12:21 ldodds: hey danbri -- I owe you a response :) ... I think its a little on the obscure side 12:22 ldodds: I see where you're coming from, but not sure its right. Its the other meaning of "apropros" that comes to mind first 12:23 ldodds: Also see your point re: isAbout 12:23 danbri: yeah, it's so tricky finding a nice word for rdf properties. Re 1st sense, maybe the concept 'fits' the thing? 12:23 ldodds: I was wondering whether we could borrow stuff from library/thesauri aspects of skos 12:23 ldodds: catalogues? 12:23 danbri: catalogues in what sense? 12:24 ldodds: As in "This Concept catalogues Gordon Brown" 12:24 ldodds: I'm not sure thats right either, but was thinking along lines of saying that a concept organizes material about something 12:24 danbri: timbl argued that foaf:knows would be better with a noun phrase, eg. foaf:contact 12:24 danbri: and i think avoiding verbs in the relation does make some sense 12:24 ldodds: ok 12:24 danbri: but i don't know really 12:25 danbri: if you consider any single rdf vocab, you might get some stylistic consistency 12:25 danbri: but since they're all used together, it is necessarily pretty chaotic 12:25 ldodds nods 12:25 danbri: 'focus' 12:25 danbri: the concept 'focusses on' the thing? 12:25 ldodds: ooh, thats nicer 12:26 danbri: or 're' 12:26 danbri: for 'regarding' 12:26 ldodds: theme? 12:26 danbri: we had 'theme' in foaf before, for something libby made up 12:26 ldodds: ah 12:26 ldodds: I like focus though 12:26 danbri: http://xmlns.com/foaf/spec/#term_theme 12:26 danbri: 'The theme property is rarely used and under-specified. The intention was to use it to characterise interest / themes associated with projects and groups. Further work is needed to meet these goals. ' 12:27 danbri: (and marked archaic) 12:27 ldodds: I missed that 12:27 ldodds: could be re-purposed I guess 12:27 danbri: foaf:focus is at least nice sounding, alliterative 12:27 ldodds: yes 12:28 danbri: focus might work better as a property of a project, the area it focusses on? 12:29 ldodds: maybe. 12:29 ldodds looks for synonyms 12:30 danbri is at dictionary.com :) 12:31 ldodds: theme suggests there may be several (un-related) themes for a concept, which isn't quite what we want to exporess 12:31 ldodds: focus is more explicit: this is what this category or concept is "about"