Proposal for ISSUE-40 Skolemization

Below is a complete proposal including intro text and detailed wording about the .well-known mechanism, based on a combination of the original proposal from the wiki, and PatH's comments. It's also on the wiki here:

On 28 Apr 2011, at 06:10, Pat Hayes wrote:
> I would prefer to avoid the "skolem" terminology altogether.

I am fine with avoiding “skolem”. But I believe that *some* term is necessary. First, writing the spec is awkward if one has to repeatedly refer to “an IRI that has been introduced solely to replace a blank node”. Second, I believe that eventually we and others will come to use *some* shorthand term in everyday technical conversation, so why not just bite the bullet and define a term for it in the spec.

I'll stick to “Skolem IRI” for now, until another term has been proposed. I removed mentions of “Skolemization”.

> it really ought to be capitalized, as it is a direct use of the name of Theo Skolem.

Thoralf. I have now capitalized the term.

> It is not clear what is meant by " identifiable by other systems". Identifiable as being skolem URIs? Or in some stronger sense of 'identifiable'? If the former, I suggest the wording "identifiable by other systems as Skolem URIs"

This wording seems fine. I ended up using “recognizable outside of the system boundaries” to avoid “identify” and talking about “systems and other systems”.

The complete proposal is below.



Add the following in RDF Concepts, Section 6.6 Blank Nodes

6.6.1 Replacing blank nodes with IRIs

Blank nodes do not have an intrinsic name in the RDF abstract syntax. In situations where such a name is required, implementations MAY systematically replace blank nodes in an RDF graph with IRIs. Systems wishing to do this SHOULD mint a new, globally unique IRI for each blank node. Such IRIs are known as ''Skolem IRIs''.

Systems may wish to mint Skolem IRIs in such a way that they can recognize the IRIs as having been introduced solely to replace a blank node, and map back to the source blank node where possible.

Systems which want Skolem IRIs to be recognizable outside of the system boundaries SHOULD use a well-known IRI [RFC5785] with the registered name “SteveH”. This is an IRI that uses the HTTP or HTTPS scheme, or another scheme that has been specified to use well-known IRIs; and whose path component starts with /.well-known/SteveH/ .

For example, the authority responsible for the domain “” could mint the following recognizable Skolem IRI:

Note: “SteveH” is a placeholder. Names currently under discussion are “genid”, “bnode”, “skolem”.

Note: RFC 5758 only specifies well-known URIs, not IRIs. For the purpose of this document, a well-known IRI is any IRI that results in a well-known URI after IRI-to-URI mapping [RFC3987].

Received on Thursday, 12 May 2011 11:47:46 UTC