modelling issue?

During Vocamp Glasgow, I tried to confront my difficulties in identifying
some domain range of few vocabularies that I started rdfizing as practice,
and from explosing my questions to a whole range of RDF doctors (thanks
Norm, Keith, Serge) two things emerged, that i did not know before

1) an entity (class, object, subject) does not necessarily have domain
/range

Is that so, and what's the rule/ and possibly exceptions/ that can be
inferred and applied?

that did not emerge at Vocamp


2) Apparently a triple can be of two kinds:

class:relation:class

 but also
class:attribute:value

Of this i would like some confirmtion (is this right?),
Finally,  finally, wouldnt' this ambiguity be confusing?

i dont have a case study for this yet, but if this is true I suspect it
could cause some possible  logical conflict/ambiguity
in semantic data model and its implementation
am I the only one thinking so?


Are the above points addressed in some RDF tutorial

please enlighten!
thanks a lot

PDM