#acl Thomas Goette:read,write All:read ## page was renamed from WikidataCheatSheet ## page was renamed from Datasets/WikidataExplanations This page provides various explanations that are useful when working the Wikidata and its peculiar schema. A good SPARQL tutorial specifically for Wikidata and its particular schema can be found here: https://www.wikidata.org/wiki/Wikidata:SPARQL_tutorial Standard prefixes can be found [[https://www.mediawiki.org/wiki/Wikibase/Indexing/RDF_Dump_Format#Prefixes_used|here]] <> = Ranking entities = == Ranking by the number of sitelinks == A sitelink is a Wikipedia page that is about a certain Wikidata entity. The number of sitelinks is a good proxy for the popularity of an entity. For example, to get all German cities and their population ordered by the number of sitelinks, one can write the following. If you [[https://goo.gl/QhjjuL|run the query on the Wikidata Query Service]] (which only works with a relatively small LIMIT), note how in the top results there is strong correlation to population size. {{{ PREFIX wd: PREFIX wdt: PREFIX rdfs: PREFIX schema: PREFIX wikibase: SELECT ?label ?population ?sitelinks WHERE { ?city wdt:P31 wd:Q515 . # ?city "instance of" "city" ?city wdt:P17 wd:Q183 . # ?city "country" "Germany" ?city wdt:P1082 ?population . # ?city "population" ?population ?city rdfs:label ?label . ?city ^schema:about/wikibase:sitelinks ?sitelinks . FILTER (LANG(?label) = "en") } ORDER BY DESC(?sitelinks) }}} An alternative measure is the number of statements of a particular entity. This often gives unintuitive results, because there are many entities with a large number of "artificial" triples (for example, all kinds of IDs), without necessarily being particulary popular. {{{ PREFIX wd: PREFIX wdt: PREFIX rdfs: PREFIX schema: PREFIX wikibase: SELECT ?label ?population ?statements WHERE { ?city wdt:P31 wd:Q515 . # ?city "instance of" "city" ?city wdt:P17 wd:Q183 . # ?city "country" "Germany" ?city wdt:P1082 ?population . # ?city "population" ?population ?city rdfs:label ?label . ?city ^schema:about/wikibase:statements ?statements . FILTER (LANG(?label) = "en") } ORDER BY DESC(?statements) }}} Note that the schema:about and wikibase:sitelinks and wikibase:statements information requires the ''full'' Wikidata dataset. These predicates are not part of the ''truthy''version. Also note that the dot before the FILTER clause is not necessary according to the SPARQL standard, but QLever currently (07.02.2020) still requires it. == Ranking by number of triples == A simpler way to rank entities and which also works with the ''truthy'' data, is to order entities by the number of triples in which they are used as subject. This works well for some queries (like the following), but not so well for others (because there are quite a lot of relatively "unimportant" entities, but which have a lot of "phony" triples; TODO: give an example). {{{ PREFIX wd: PREFIX wdt: PREFIX rdfs: PREFIX schema: PREFIX wikibase: SELECT ?label ?population (COUNT(?label) AS ?popularity) WHERE { ?city wdt:P31 wd:Q515 . ?city wdt:P17 wd:Q183 . ?city wdt:P1082 ?population . ?city rdfs:label ?label . ?city ?p ?o . FILTER (LANG(?label) = "en") } GROUP BY ?label ?population ORDER BY DESC(?popularity) LIMIT 100 }}} = Obtaining names = == Names for entities == The [[https://query.wikidata.org|Wikidata Query Service (WDQS)]] has an automatic mechanism for obtaining the single best name for entity variables in the query. It does not work for predicate names, however. The mechanism is invoked by adding this line to the SPARQL query: {{{ SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". } }}} To obtain a single name of an entity "manually" (= without the mechanism above), one can add the following two lines to a query ([[https://www.wikidata.org/wiki/Q90|Q90]] is Paris). Note that without the language filter, one gets one name for each languages, for which a name has been specified for that entity in Wikidata (for popular entities, these are usually very many): {{{ wd:Q90 rdfs:label ?label . FILTER (LANG(?label) = "en") }}} == Names for predicates == Obtaining the name for a predicate is a bit more complicated. Here is how to obtain all predicates and their English name for an entity (again Q90), sorted by the number of triples with that predicate and that entity as subject: {{{ PREFIX wd: PREFIX wikibase: PREFIX rdfs: SELECT ?p (COUNT(?o) as ?count) (SAMPLE(?label) as ?pname) WHERE { wd:Q90 ?p ?o . ?x wikibase:claim ?p . ?x rdfs:label ?label . FILTER (LANG(?label) = "en") } GROUP BY ?p ORDER BY DESC(?count) LIMIT 100 }}} There are a number of other wikibase: predicates that relate the different types of predicates to teach other {{{ wd:P47 wikibase:claim p:P47 wd:P47 wikibase:directClaim wdt:P47 wd:P47 wikibase:novalue wdno:P47 wd:P47 wikibase:qualifier pq:P47 wd:P47 wikibase:qualifierValue pqv:P47 wd:P47 wikibase:reference pr:P47 wd:P47 wikibase:referenceValue prv:P47 wd:P47 wikibase:statementProperty ps:P47 wd:P47 wikibase:statementValue psv:P47 }}} == Aliases of an entity == In the .nt file, Aliases are expressed as follows {{{ "Angela Dorothea Merkel"@de }}} There are also some other predicates, which provide alternative names, see [[https://stackoverflow.com/questions/40593452/how-to-retrieve-aliases-from-wikidata|this question on Stackoverflow]]. To get all aliases of an entity according to that list write something like this: {{{ PREFIX wd: PREFIX wdt: PREFIX skos: PREFIX rdfs: SELECT ?alias WHERE { wd:Q567 (wdt:P735|wdt:P734)?/(wdt:P1813|wdt:P1705|wdt:P1559|wdt:P1477|wdt:P1449|wdt:P742|skos:altLabel|rdfs:label) ?alias . FILTER (LANG(?alias) = "en") } }}} The predicates ''wdt:P735'' and ''wdt::P734'' yield the ''given name'' and ''family name'', respectively. Note that the objects of the predicates are entities, not literals. The ? after the (...) means that sequences of length 0 or 1 of these predicates are considered (that is using one of the predicates or not). With * one would get all sequences of length >= 0. For the query above, this would give the same result. With + one would get all sequences of length >= 1. For the query above, this would give fewer results, because we would not get the names of only ''wd:Q567''. The predicates ''wdt:P1813'', ''wdt:1705'', ''wdt:P1559'', ''wdt:P1477'', ''wdt:P1449'', ''wdt:P742'', ''skos:altLabel'' and ''rdfs:label'' yield ''short name'', ''native label'', ''name in native language'', ''birth name'', ''nickname'', ''pseudonym'', ''aliases'' and ''unique (per language)'' label, respectively. The objects for these predicates are literals. Note that the literals from ''skos:altLabel'' are in general not a superset of the literals from ''rdfs:label''. For the sake of completeness, one could include ''wdt:P297'' and ''wdt:P298'', which yield the two- and three-letter ISO codes for countries, or ''wdt:P1160'', which yields the ISO 4 abbreviation. There are probably some others which could be relevant as well in some cases. Note that ''skos'' stands for ''simple knowledge organization system''. The ''simple'' is obviously a joke, given that the full URI is http://www.w3.org/2004/02/skos/core#altLabel . Also note that the ''FILTER'' might be too strict. For example, the query will not get the name 'Brünneck' for ''Wiltraut Rupp-von Brünneck'' (wd:Q1000023). This is because the family name ''Brünneck'' (wd:Q100264946) has (at the time of writing) only a German label and a German native label, but no English or multi-language labels. == Aliases of a predicate == The following query gives names and aliases for any predicate that is connected (via one of the ''wikibase:...'' predicates above) to a ''wd:...'' entity. {{{ PREFIX skos: PREFIX rdfs: PREFIX p: SELECT ?name_or_alias WHERE { ?predicate_entity ?p p:P40 . ?predicate_entity rdfs:label|skos:altLabel ?name_or_alias . FILTER (LANG(?name_or_alias) = "en") . } }}} = Statements and value-qualifier tuples for an entity = For example, all (population, point in time) pairs for Paris (Q90): {{{ PREFIX p: PREFIX ps: PREFIX pq: PREFIX wd: SELECT ?value ?time WHERE { wd:Q90 p:P1082 ?statement . # P1082 = population ?statement ps:P1082 ?value . # P1082 = population ?statement pq:P585 ?time # P585 = point in time } ORDER BY DESC(?time) }}} = Problems with the Wikidata schema = == Query: City, country, population == 1. Many cities in Wikidata are not "instance of" (wdt:P31) "city" (wd:Q515), but "big city" (wd:Q4905452), which in turn is a "subclass of" (wdt:P279) city. Many of the example queries in Wikidata therefore use the following triple to specify that a variable is a city: {{{ ?city wdt:P31/wdt:P279* wd:Q515 }}} 2. Unlike Freebase, Wikidata has a property "country" (wdt:P17) to relate items (in particular: cities) to their countries. There is also "contains administrative territorial entity" (wdt:P150), but it is much less complete: the first query below has a result with ''10,560,170'' rows, the second query has a result with only ''21,344'' rows. {{{ PREFIX wdt: SELECT ?city ?country WHERE { ?city wdt:P17 ?country . } }}} {{{ PREFIX wdt: PREFIX wd: SELECT ?city ?country WHERE { ?city wdt:P31/wdt:P279* wd:Q515 . ?country wdt:P31 wd:Q6256 . ?city wdt:P17 ?country } }}}