The cultural frame (or framework) of a piece of art is it's social and cultural context.
Artists are nearly always influenced in some way by what other artists have done in the past and what their contemporaries are doing, they are also influenced by other events, social, political, economic, cultural, etc. The combination of these influences is the context (frame) within which an art work is created.
Post-modernism does not defy definition. It was originally a term applied to architecture that had moved away from the Modernist style (form follows function, no extraneous detail or decoration etc) and was using an eclectic mix of styles and forms derived from various periods.
It soon became applied to any art form that used similar ideas.
"Subjective" refers to the personal response of the viewer.
PS. Frank Stella was important in the 70s but not "the most influential" artist.
What is "midevil"? some sort of half-baked black magic I presume.
PPS. Ooer! All I did was to mildly disagree with a viewpoint.
Frank Stella's importance is a matter of opinion, others might not concur with the cited sources. Also I notice that it's been modified from "artist" to "in abstract art".
"Sports" says you can't define post-modernism and then proceeds to try and do so. All I suggested was that a definition of sorts already exists.
There's no need to take things so personally.
(The somewhat snobbish comment about Ireland is unnecessary and irrelevant. I was born in the UK and studied Fine Art for many years in London. I'm fully aware of American "superstar" artists and their importance.)