Matters

Re: Proposed issue: What does using an URI require of me and my software? from Tim Berners-Lee on 2003-09-26 (public-sw-meaning@w3.org from September 2003)
"cwm will operate in a number of modes with respect to looking
stuff up as a function of the URIs loaded into the knowledge base.

cwm --closure=flags

where flags are a combination of
p - look up predicates
s - look up subjects
o - look up objects
t - look up the object only where the predicate is rdf:type

An interesting mode is cwm --closure=pt.
Lets call this "ontological closure".
It is a reasonable thing to do, as it adds to the KB the
machine-readable
information which is assumed shared by the writer and reader of
a document. If people do this a lot, then it useful to write
documents whose
ontological closure is of a manageable size. This is the case with any
real RDF files I've tried. It is what you might expect - people define
ontologies using ontologies but only to a limited level.

Contrast with --closure=spo which pulls in the whole contiguous
semantic web starting at the given document. This is not practical.
This is interesting, as it highlights a difference between p and s and
o
not only in the spec but in the topology of the web."