- From: Steve Harris <steve.harris@garlik.com>
- Date: Fri, 18 Nov 2011 11:21:00 +0000
- To: gouadjed@eoweo.com
- Cc: semantic-web@w3.org
Jena supports SPARQL 1.1, so you should be able to do a query something like: SELECT (COUNT(?friends) AS ?num_friends) WHERE { <person> foaf:knows ?friends } You can put this in a subquery if you need to use the number in other parts of the query. - Steve On 2011-11-18, at 10:53, Ghalem Ouadjed (EOWEO) wrote: > Thank you for your answers. > > i had to precise that i m wroking on a closed application and even if foaf doesn t contain the property i need the query works on Jena... > > to be less specific, i would like to know how to look for a schema based on a specific need regarding the property ? is there a way to determine that there is one or more schema which contain one or more property i envision to use. This could help to decide if i have to write a lightweight one or to use an existing one... > > I can realize that this kind of problematics doesn t correspond to a dogmatic vision but i know and experiment the needs of some middle size companies aiming to use semantic technologies in a pragmatic way for closed applications like internal KM solutions for instance and why not which could be enhanced and contextualised by linked datas... > > Thank you again for your time > > Cheers > Ghalem > > Le 18/11/2011 10:33, Heiko Paulheim a écrit : >> Due to the open world assumption, the value of that counter would (probably) we wrong. >> >> If I have >> :Peter foaf:knows :Stephen . >> :Peter foaf:knows :Marc . >> >> and, based on that knowledge, I added >> >> :Peter myschema:friendnb "2"^^xsd:integer . >> >> this would not be a valid conclusion - there may be a lot more friends of Peter which are not in my knowledge base (don't we all have friends without a facebook account?), and :Stephen and :Marc might even refer to the same person. In other words, with that approach, I would add knowledge to my knowledge base which is potentially wrong. >> >> So I would rather refrain from doing that. >> >> Best, >> Heiko. >> >> Am 18.11.2011 10:28, schrieb Melvin Carvalho: >>> On 18 November 2011 10:20, Heiko Paulheim<paulheim@ke.tu-darmstadt.de> wrote: >>>> Dear Ghalem, >>>> >>>> since such a property would be in a conflict with the open world assumption >>>> underlying the semantic web (you simply cannot tell "how many things of type >>>> X are there" in an open world), I suppose there is no serious schema which >>>> has such a property. >>> What if you kept a separate tally to aggregate total friends as they are added? >>> >>>> Best, >>>> Heiko. >>>> >>>> >>>> >>>> Am 17.11.2011 18:40, schrieb Ghalem Ouadjed (EOWEO): >>>> >>>> Hi everyone, >>>> i would like to use a schema which is different and complementary of the >>>> foaf one, and which could contain a property like "number of friends". >>>> >>>> Does someone know an available ontology i could use pls? >>>> >>>> one of my query would look like : >>>> >>>> PREFIX rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" >>>> PREFIX rdfs="http://www.w3.org/2000/01/rdf-schema#" >>>> PREFIX dc="http://purl.org/dc/elements/1.1/" >>>> PREFIX foaf="http://xmlns.com/foaf/0.1/" >>>> PREFIX ............="_" >>>> >>>> SELECT ?friendnb WHERE { ?Person ...;;;;:friendnb ?friendnb } >>>> ------------ >>>> | friendnb | >>>> ============ >>>> | "\n330\n" | >>>> ------------ >>>> Thank you in advance for your advices and your time >>>> >>>> Cheers >>>> Ghalem >>>> >>>> -- >>>> Dr. Heiko Paulheim >>>> Knowledge Engineering Group >>>> Technische Universität Darmstadt >>>> Phone: +49 6151 16 6634 >>>> Fax: +49 6151 16 5482 >>>> http://www.ke.tu-darmstadt.de/staff/heiko-paulheim >> >> >> > -- Steve Harris, CTO, Garlik Limited 1-3 Halford Road, Richmond, TW10 6AW, UK +44 20 8439 8203 http://www.garlik.com/ Registered in England and Wales 535 7233 VAT # 849 0517 11 Registered office: Thames House, Portsmouth Road, Esher, Surrey, KT10 9AD
Received on Friday, 18 November 2011 11:21:38 UTC