Re: Propagation of bad sameAs statements
Hi, Thank you for your interest. Here are some sort of answers to this and other questions. In fact, this has become something of a dialogue with myself :-) sameas.org does not itself do any interesting inference, other than A sameas B B sameas C = A sameas C when asked about A. It aims to gather equivalence information from existing sources and service the results in a convenient (single) place. (It also aims to address the problem of owl:sameas being a pairwise statement, which gives an unpleasant explosion (n**2) of statements for groups of equivalences, which can be quite hard to handle.) Who chooses what data is acceptable? Er, me. I look at it and decide. Is it a spider (people sometimes ask this)? No - when I am bored with the other things I am doing I add more to it, by downloading dumps or querying SPARQL endpoints, often as a result of messages on this and other lists. Is owl:sameAs the only predicate recognised? As you have worked out, no. It is a service giving equivalent URIs, and one of the formats you can get back is owl:sameAs. But you can get other formats if you want. So the inputs include things like skos:exactMatch and skos:closeMatch (as I recall). And we could output other formats such as these if asked. At the moment we only do rdf+xml, text/n3, application/json, text/plain, see http://www.sameas.org/about.php. What has now been noticed is that I decided that dbpedia redirects should be treated as equivalent. The reason I did this is that it meant that a lot of expected URIs now worked. Eg http://dbpedia.org/resource/UN/LOCODE:GBLON and even http://dbpedia.org/resource/Capital_of_the_UK get to http://data.ordnancesurvey.co.uk/id/70041428 and http://statistics.data.gov.uk/id/eer/07. The downside is that there is quite a lot of cruft in the redirects, and so some strange things happen (as has been observed). Do I know about errors in sameas.org? Yes. I like the Iron Maiden one to opencyc, for example. But I don't aim to correct these, any more than Google aims to correct things it links to. Why such a liberal attitude to equivalence? I eventually worked out that sameas.org was a discovery service. We have other sameas services, called crs services, on our systems (eg http://opencyc.rkbexplorer.com/crs/ is an external one) which are definitional (I hesitate to use a word like authoritative, with all its other connotations). And so in that vein, I have cast the net wider for sameas.org. This was the case early in its life, as the wordnet equivalence to dbpedia is in fact the equivalence of the word to the thing, which is wrong at some/any level. But I have taken the view that people/agents that come to sameas.org are looking for things, and might not care about such subtleties, not least because they may not have understand them when they constructed their RDF. If I had the time/funding, I would provide other services that took different views of equivalence, in terms of discovery/definitional or liberal/conservative (precision/recall is another way of saying that). Mind you it is probably the case that the sameas.org data is no worse than a lot of the data in the LOD diagram, in terms of reliably identifying resources, as I have rejected a bunch of them as being substandard. On 08/09/2010 15:42, joel sachs jsa...@csee.umbc.edu wrote: ... So, a request for the sameas.org folks: Would it be possible to include a provenance column for all sameAs assertions you keep track of? In cases where the sameAs assertion isn't actually asserted on the web, you could indicate the provenance as inferred in the provenance column. Also, have you published the heuristics you use (if any) to infer sameAs relations? ... Thanks! Joel. So finally getting round to your specific question (although hopefully the other stuff has also helped). It would be hard to provide the extra column for quite a few reasons. We do know where we got the data from, but it may be a SPARQL endpoint, a dump downloaded, or an email sent to me, for examples. So it would not be very easy to interpret. But only a small number of the pairs would be so identified, as all the rest are inferred from the other pairwise assertions. We can actually have our own visualisation tools for bundles, with assertions and dates, etc, but the tool is hard to read if you don't know what is happening, and... 1) Finding the resources to make it more accessible would be hard. sameas.org has effectively never been funded - it is my hobby with Ian Millard, and we would love to have the resources to do this sort of stuff. I actually have plans for a more sophisticated architecture behind sameas.org which facilitate this and a lot of other stuff, but again it is a question of resources. 2) What is the Ontology? A big question with giving more information is, what is the ontology? We live in the Linked Data world (for sameas.org), and machine-interpretable structures. So sameas.org is designed to be used by services, and
Re: Propagation of bad sameAs statements
Hugh, Great to understand how this all works. I'm now expecting somebody to take all these sameAs links and run some type of page rank algorithm and rank what actually is sameAs. Cheers Juan Sequeda +1-575-SEQ-UEDA www.juansequeda.com On Thu, Sep 9, 2010 at 8:23 AM, Hugh Glaser h...@ecs.soton.ac.uk wrote: Hi, Thank you for your interest. Here are some sort of answers to this and other questions. In fact, this has become something of a dialogue with myself :-) sameas.org does not itself do any interesting inference, other than A sameas B B sameas C = A sameas C when asked about A. It aims to gather equivalence information from existing sources and service the results in a convenient (single) place. (It also aims to address the problem of owl:sameas being a pairwise statement, which gives an unpleasant explosion (n**2) of statements for groups of equivalences, which can be quite hard to handle.) Who chooses what data is acceptable? Er, me. I look at it and decide. Is it a spider (people sometimes ask this)? No - when I am bored with the other things I am doing I add more to it, by downloading dumps or querying SPARQL endpoints, often as a result of messages on this and other lists. Is owl:sameAs the only predicate recognised? As you have worked out, no. It is a service giving equivalent URIs, and one of the formats you can get back is owl:sameAs. But you can get other formats if you want. So the inputs include things like skos:exactMatch and skos:closeMatch (as I recall). And we could output other formats such as these if asked. At the moment we only do rdf+xml, text/n3, application/json, text/plain, see http://www.sameas.org/about.php. What has now been noticed is that I decided that dbpedia redirects should be treated as equivalent. The reason I did this is that it meant that a lot of expected URIs now worked. Eg http://dbpedia.org/resource/UN/LOCODE:GBLON and even http://dbpedia.org/resource/Capital_of_the_UK get to http://data.ordnancesurvey.co.uk/id/70041428 and http://statistics.data.gov.uk/id/eer/07. The downside is that there is quite a lot of cruft in the redirects, and so some strange things happen (as has been observed). Do I know about errors in sameas.org? Yes. I like the Iron Maiden one to opencyc, for example. But I don't aim to correct these, any more than Google aims to correct things it links to. Why such a liberal attitude to equivalence? I eventually worked out that sameas.org was a discovery service. We have other sameas services, called crs services, on our systems (eg http://opencyc.rkbexplorer.com/crs/ is an external one) which are definitional (I hesitate to use a word like authoritative, with all its other connotations). And so in that vein, I have cast the net wider for sameas.org. This was the case early in its life, as the wordnet equivalence to dbpedia is in fact the equivalence of the word to the thing, which is wrong at some/any level. But I have taken the view that people/agents that come to sameas.org are looking for things, and might not care about such subtleties, not least because they may not have understand them when they constructed their RDF. If I had the time/funding, I would provide other services that took different views of equivalence, in terms of discovery/definitional or liberal/conservative (precision/recall is another way of saying that). Mind you it is probably the case that the sameas.org data is no worse than a lot of the data in the LOD diagram, in terms of reliably identifying resources, as I have rejected a bunch of them as being substandard. On 08/09/2010 15:42, joel sachs jsa...@csee.umbc.edu wrote: ... So, a request for the sameas.org folks: Would it be possible to include a provenance column for all sameAs assertions you keep track of? In cases where the sameAs assertion isn't actually asserted on the web, you could indicate the provenance as inferred in the provenance column. Also, have you published the heuristics you use (if any) to infer sameAs relations? ... Thanks! Joel. So finally getting round to your specific question (although hopefully the other stuff has also helped). It would be hard to provide the extra column for quite a few reasons. We do know where we got the data from, but it may be a SPARQL endpoint, a dump downloaded, or an email sent to me, for examples. So it would not be very easy to interpret. But only a small number of the pairs would be so identified, as all the rest are inferred from the other pairwise assertions. We can actually have our own visualisation tools for bundles, with assertions and dates, etc, but the tool is hard to read if you don't know what is happening, and... 1) Finding the resources to make it more accessible would be hard. sameas.org has effectively never been funded - it is my hobby with Ian Millard, and we would love to have the resources to do this sort of stuff.
Propagation of bad sameAs statements
I'd like to catalog sources of biodiversity information and misinformation on the semantic web, and am trying to determine the genesis of some unfortunate owl:sameAs statements. According to sameas.org: http://dbpedia.org/resource/Invasive_species owl:sameAs http://dbpedia.org/resource/Invasive_plant http://dbpedia.org/resource/Invasive_animal http://dbpedia.org/resource/Invasive_organism http://rdf.freebase.com/ns/guid.9202a8c04000641f8007de24 (many other concepts) Checking out the dbpedia resources that are the objects of the sameAs assertions, we see that each redirects to http://dbpedia.org/resource/Invasive_species. But other than dbpedia:Invasive_species including a sameAs link to freebase:Invasive_species, no dbpedia page, afaict, makes the sameAs assertions listed above. However, http://rdf.freebase.com/rdf/guid.9202a8c04000641f8007de24 does assert: http://rdf.freebase.com/ns/guid.9202a8c04000641f8007de24 owl:sameAs http://dbpedia.org/resource/Invasive_species http://dbpedia.org/resource/Invasive_plant http://dbpedia.org/resource/Invasive_organism http://dbpedia.org/resource/Invasive_animal etc. The direction of propagation is not explicit. One possibility is that sameas.org is inferring that A sameAs B based on A redirects to B, and that these assertions are making their way into freebase. Another is that a freebase contributor is making the sameas inferences, and that they are being picked up by sameas.org. (Similar cycles of sameAs can be found for habitat, introduced_species, and many other concepts.) So, a request for the sameas.org folks: Would it be possible to include a provenance column for all sameAs assertions you keep track of? In cases where the sameAs assertion isn't actually asserted on the web, you could indicate the provenance as inferred in the provenance column. Also, have you published the heuristics you use (if any) to infer sameAs relations? And questions for freebase contributors: Are any of you running a script that either a) loads in assertions from sameas.org, or b) deduces sameAs relations from dbepedia redirection behaviour? Thanks! Joel.
Re: [Freebase-discuss] Propagation of bad sameAs statements
[ Crossposting. Apologies for the duplicate. ] - Forwarded message from Philip Kendall philip-freeb...@shadowmagic.org.uk - From: Philip Kendall philip-freeb...@shadowmagic.org.uk To: freebase-disc...@freebase.com Subject: Re: [Freebase-discuss] Propagation of bad sameAs statements Date: Wed, 8 Sep 2010 15:55:31 +0100 On Wed, Sep 08, 2010 at 10:42:45AM -0400, joel sachs wrote: And questions for freebase contributors: Are any of you running a script that either a) loads in assertions from sameas.org, or b) deduces sameAs relations from dbepedia redirection behaviour? Essentially, (b) - they're deduced from Wikipedia rather than dppedia, but it comes down to the same thing. I agree with you that it's the wrong thing to do - hopefully one of the Freebase Data Team will be along to explain why they do it. Cheers, Phil -- Philip Kendall phi...@shadowmagic.org.uk http://www.shadowmagic.org.uk/ - End forwarded message - -- Philip Kendall phi...@shadowmagic.org.uk http://www.shadowmagic.org.uk/
Re: [Freebase-discuss] Propagation of bad sameAs statements
On Wed, Sep 8, 2010 at 10:59 AM, Philip Kendall philip-freeb...@shadowmagic.org.uk wrote: [ Crossposting. Apologies for the duplicate. ] - Forwarded message from Philip Kendall philip-freeb...@shadowmagic.org.uk - From: Philip Kendall philip-freeb...@shadowmagic.org.uk To: freebase-disc...@freebase.com Subject: Re: [Freebase-discuss] Propagation of bad sameAs statements Date: Wed, 8 Sep 2010 15:55:31 +0100 On Wed, Sep 08, 2010 at 10:42:45AM -0400, joel sachs wrote: And questions for freebase contributors: Are any of you running a script that either a) loads in assertions from sameas.org, or b) deduces sameAs relations from dbepedia redirection behaviour? Essentially, (b) - they're deduced from Wikipedia rather than dppedia, but it comes down to the same thing. I agree with you that it's the wrong thing to do - hopefully one of the Freebase Data Team will be along to explain why they do it. It may be to allow any URL that refers (or referred) to a Wikipedia page to be mechanically transformed into a valid Freebase URL, but Wikipedia redirects are a mishmash of valid alternative names, misspellings, and names of completely separate concepts which were merged because they weren't big or significant enough to warrant their own Wikipedia page. I agree that it would be much better to have a single sameAs between the concepts and to keep the information from the redirects as alternate labels (if at all). Speaking of DBpedia/Freebase sameAs links, the DBpedia side of things shouldn't be using internal Freebase GUIDs. They should either be using the standard IDs or, preferably, the relatively new MIDs i.e. one of the following: http://rdf.freebase.com/rdf/m.0hrk4 http://rdf.freebase.com/rdf/en.invasive_species As an aside, Freebase should also be using owl:sameAs to link these alternate identities together. Tom
