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I am new to SPARQL, OWL and the knowledge base Yago2s. I have been reading about entity linking which is basically a process of finding named entities in online textual documents and linking them to the entities in knowledge base like Yago2s. For example: if a sentence goes like "Page and Brin founded Google", then Page and Brin are linked to entries of Larry_Page and Sergey_Brin in Yago2s respectively.

I have read that there is a relation(property) defined in Yago called means relation which does this kind of mapping i.e. it gives all possible entities defined in Yago which the phrase detected in the document can mean. eg: Obama can mean Barack_Obama, Michelle_Obama etc. However, I can't seem to find any such property defined in Yago2s. But, there is a property called rdfs:label which kind of does the same thing.

I have two questions:-

  1. Has the means relation been replaced by rdfs:label
  2. Is there any kind of tutorial or online manual, where all the properties defined in Yago2s are mentioned and defined briefly so that I can have a look and accordingly construct my SPARQL query.

Thanks in advance.

Joshua Taylor
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AvinashK
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1 Answers1

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1) No. rdfs:label is a relationship to create human readable descriptions of a given resource name (http://www.w3.org/TR/rdf-schema/#ch_label). For example, if I have a class with the URI "http://example.org/aabbc" which is used to represent "Trees" I would add the following triple:

<http://example.org/aabbc> rdfs:label "Tree"@eng

Although I havent't found a description of the yago:means relationship, it seems that it is meant to link together resources that mean the same thing. In YAGO, they exploit this relationship to link resources (from http://pubman.mpdl.mpg.de/pubman/item/escidoc:1819115:2/component/escidoc:1840732/MPI-I-2006-5-006.pdf):

"if the user typed ”Einstein, Albert” instead of ”Albert Einstein”, then there is a virtual redirect page for ”Einstein, Albert” that links to ”Albert Einstein”. We exploit the redirect pages to give us alternative names for the entities. For each redirect, we introduce a corresponding means fact (e.g. (”Einstein, Albert”, means, Albert Einstein))."

What this means is that they create two different entities, with their respective URIs (one for "Albert Einstein" and another for "Einstein, Albert"), and they link it through the "means" property. They are not linking the literals directly, as you can't use a literal as a domain for a property.

Therefore, if you want to create links between your resources and Yago you could do so by:

  • Show the yago's link directly (If you show html in your pages)
  • Use your document URI as the domain and state something like "refersTo" or "linksTo" the Yago entity (if you want to just link your document as a whole to Yago) :

yourDocURI yourdomain:refersTo yagoEntityFound

  • Create a URI for the word and specify the equivalent individual with and owl:sameAs link (http://www.w3.org/TR/owl-ref/#sameAs-def) (If you want to state that some words of your document link to yago's resources):

http://example.org/wordPage owl:sameAs yagoEntityLarryPage

2) Yago is a huge ontology and navigating it might be tricky. However I found this: https://gate.d5.mpi-inf.mpg.de/webyagospotlx/Browser which might do the trick. I hope it helps. Also, YAGO uses the wordnet definitions, so it might help you to take a look there.

By the way, I don't see why you need to perform any sparql queries here.

Daniel Garijo
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  • @Daniel...thanks for the answer...In the link to the pdf file that you have provided in your answer, means relation is discussed on the sixth page and the again on the seventeenth page. On the 17th page, they say that FamilyNameOf and GIvenNameOf are both subrelations of the MEANS relation. So there should be a MEANS relation somewhere in the entire Yago. Isn't it?...If yes then can you please tell me how to find it? Thanks – AvinashK Oct 08 '14 at 06:55
  • @Daniel...I searched YagoSchema.ttl where they claim to list all the relations. But there was no means relation – AvinashK Oct 08 '14 at 06:56
  • @avinash: I have been looking at the schema and you are right. Furthermore, FamilyNameOf and GIvenNameOf are not defined either, but "hasFamilyName" and "hasGivenName" (the inverses), exist. Maybe the "means" relationship is something they do not assert in their resources, but something they use to create their text equivalences. For example, if you search: "Einstein, Albert" here: https://gate.d5.mpi-inf.mpg.de/webyagospotlx/SvgBrowser?entityIn=Einstein%2C+Albert&codeIn=eng you get redirected to "Albert Einstein". It is not as strong as the means relationship, but it is what they use – Daniel Garijo Oct 08 '14 at 08:51
  • Anyway, for your purposes I don't think you need the "means" relationship. That is something they use in Yago to produce their data. You can opt to do any of the three alternatives I posted on my response. – Daniel Garijo Oct 08 '14 at 08:55
  • Apart from the [link](https://gate.d5.mpi-inf.mpg.de/webyagospotlx/SvgBrowser?entityIn=Einstein%2C+Albert&codeIn=eng)...what are the other two alternatives? – AvinashK Oct 08 '14 at 09:21
  • @Daniel...I now get you..You misunderstood what I needed....When given a word(like Obama), I need to find out all the real world entities it denotes(like Michelle Obama, Barack Obama)...I don't know this mapping beforehand. Its like I am building a querying system which when given a word returns all the real entities represented by it. – AvinashK Oct 08 '14 at 09:25
  • Then you are trying to do entity recognition (which had nothing to do with the original question ;)). There are several tools for that like dbpedia spotlight (https://github.com/dbpedia-spotlight/dbpedia-spotlight/wiki/Introduction), Gate (http://stackoverflow.com/questions/6003246/use-nlp-gate-tool-for-named-entity) or Zemanta (http://www.zemanta.com/). If you want to query Yago to compare against its resources (which could be time consuming), I would go for the rdfs:label then. I hope this helps! – Daniel Garijo Oct 08 '14 at 09:55