Property talk:P2

Subclass and Same As

Wherever possible, the GeoKB leverages classification schemes from established sources of definition and semantic organization within our scientific domains. When we do so, we are using the same as property to record a resolvable URL/identifier for the concept in the foreign source. At the same time, we are working within the Wikibase/Wikidata environment, which is a bit "peculiar" in that it is expressly built to be navigated through and worked on by users in practice. One artifact of this is that labels also matter, resulting in us making a number of design decisions in how this knowledge graph is organized.

Most domain-specific classification systems focus on defining things within their specific context, which is inevitably narrower than what we are doing here (let alone what happens in the global knowledge commons). The same label in one classification scheme (e.g., a domain ontology) may have a completely different meaning in some other classification scheme. Wikipedia deals with this through the idea of disambiguation pages that link off to specific "meanings" of the same word or concept. Wikidata ends up with a mix of approaches with a basic constraint built into the Wikibase technology that allows language-specific labels to be duplicated but will not allow an item with exactly the same label and description, essentially using the description as "disambiguator."

We are testing a little bit of a different approach here in that we attempt to bring about some level of synthesis as we process and curate various reference sources into our classification scheme. Where reasonable, we expand the definition of a specific concept so that it can be more than one thing. This may result in the same item having multiple same as linkages, some of which point to different items in the same source when we determine that, for our purposes, we can link to a single entity from multiple contexts and have it provide what's necessary in our graph. This doesn't always work out in practice, and so we come back and adjust as use cases point toward the need for more granular specificity.

While it's possible for an entity in the GeoKB to be both a subclass of some higher-level class and an instance of something, we generally try to keep the classification system as "clean" as possible. One example where entities co-exist as classifiers and instances of is the idea of mineral commodity where the items are part of some other classification system (e.g., mineral classification from the Geoscience Ontology) but then act as instances of mineral commodities. We could eventually turn the "commodity" into a classification system in its own right, but for now we have a way of querying for what we need on items that are reasonably defined in an explainable way.

Full Classification

It can be necessary and useful to pull the full classification from the GeoKB, including same as links, for use in processing source material for organization here. The following query is designed to do things like provide a simple lookup mapping on the identifiers from source systems we've recorded as same as claims.

PREFIX wd: <https://geokb.wikibase.cloud/entity/>
PREFIX wdt: <https://geokb.wikibase.cloud/prop/direct/>

SELECT ?item ?itemLabel ?subclass_of ?subclass_ofLabel ?same_as 
WHERE {
  ?item wdt:P2* wd:Q2 ; # Get all subclasses (transitively) starting from "entity" as the origin
        wdt:P2 ?subclass_of .
  OPTIONAL {
    ?item wdt:P84 ?same_as . # Get any same as declarations for the classification entities
  }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en" . }
}

Try it!