Re: HTTP URIs for real world objects(B

yep, you can think, for example, an Wikipedia page as a Subject Indicator.

:me a foaf:Person; foaf:interest wikipedia:Semantic_Web .
wikipedia:Semantic_Web foaf:primaryTopic concept:Semantic_Web .

=> :me foaf:topic_interest concept:Semantic_Web .

In a sense, foaf:interest uses the object document as *an* indicator
of the subject(URI of such document is a Subject Identifier). And a
(P)SI can indicate the subject by using an IFP such as
foaf:primaryTopic.

So we can almost think that an Wikipedia page is an PSI, except it
doesn't satisfy the last requirement of PSI: "A Published Subject
Indicator must explicitly state the unique URI that is to be used as
its Published Subject Identifier" (3.1.3 in spec).

cheers,
-- 
@prefix : <http://www.kanzaki.com/ns/sig#> . <> :from [:name
"KANZAKI Masahide", "$B?@:j@51Q(B"; :email "mkanzaki@gmail.com"].