- From: Ghalem Ouadjed (EOWEO) <gouadjed@eoweo.com>
- Date: Fri, 18 Nov 2011 13:13:27 +0100
- To: semantic-web@w3.org
Hi Steve, Thank you a lot ! as usual you re incredibly effective :) Take care Ghalem Le 18/11/2011 12:21, Steve Harris a écrit : > 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 >>> >>>
Received on Friday, 18 November 2011 12:14:08 UTC