mkroetzsch added a comment.

Thanks for adding Denny. Long reply, but details matter here.

I agree that there are different things one could talk about (document, real 
thing). However, for now I am mainly interested in talking about the latter, 
since this should be our primary concern in Wikibase (the document is a thing 
MediaWiki has to care about).

Now you argue that certain triples should not be given for the real thing 
(whether related to the reified statements or to the item type). However, your 
arguments do not have an objective foundation: the only reason why you do not 
want to have certain triples is that you interpret them to mean something that 
would not be true, whereas I am interpreting the very same triples in a way 
that would be correct. In other words, we have a dispute about the meaning of 
triples.

Interestingly, the triples we discuss primarily refer to vocabulary that we 
created for the very purpose of being used in these triples. How could it mean 
the wrong thing? Only if we define it to mean the wrong thing. Therefore, let's 
just define those triples to mean the right thing and we are all set. There is 
no technical discussion to be had here; it's all about desired or undesired 
interpretations.

If you look at the RDF structures that we get if we want to represent all of 
our data (without even including its order), then it should be clear that these 
structures simply do not have any self-evident "natural" interpretation. We 
need to tell people what they mean. Let's just tell them what we think they 
should mean. The only thing to keep in mind (and this is also what you are 
saying) is that we cannot use the same URI to mean different things in 
different contexts, so we need different URIs for referring to the class of 
real-world items and for referring to the class of item documents. I do not see 
a problem with this.

An RDF document represents a graph. It is a purely abstract, mathematical 
model. Nothing is said there about the real world or about documents or about 
truth. It's all in our heads. The reason why we are so careful to distinguish 
documents from real things etc. is that we want to make sure that the data as a 
whole (taking all RDF from one site together) still makes sense. Yet, we are 
free to define this sense. We could define a property that means "is described 
on a Wikipedia page that was once edited by someone who was born in". Would 
this say something about the real George Washington? Sure.

For the same reason, please do not confuse reification in RDF (which represents 
a triple without stating that the triple is true) with reification in our 
export (which simply uses an auxiliary resource to make a statement). Using 
auxiiary nodes in RDF data is a common technique that does not have any impact 
on whether you are saying something about the real world or whether you are 
saying that a document made a certain claim. In particular, it is not any 
stronger or more direct to use one triple to represent a statement than to use 
a group of triples around an auxiliary node. You always need to document in 
your ontology what your RDF structures express.

Whether we need to use different subject URIs for simplified and for reified 
exports I don't know. Maybe it also depends on the exact way in which the 
simplified export is created. Already in our RDF exports, we are using 
different property URIs in both cases, so even in the union of the datasets 
there would never be any doubt as to which triple belongs to which view on the 
data. Moreover, many triples are the same in both views (e.g., labels). 
Therefore I am inclined to think that there is no need for different URIs 
there. (I don't see the connection to your truthy projection if you just use it 
for answering queries, unless of course you are returning query results in RDF 
so that these results would turn into another kind of RDF export that needs to 
be consistent with those we have now.)


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To: daniel, mkroetzsch
Cc: Denny, Smalyshev, mkroetzsch, Aklapper, daniel, Wikidata-bugs, Jdouglas, 
aude



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