Sorry Roy missed your first post . Arguably they are not abstract as they represent something in the consciousness of the engraver but that's really semantics and based on the thinking of the engraver having a mental impression which is then accurately transferred to the medium , that may be the case in many areas of "art " ,portraits ,some sculptures , playing from a score etc but so often it much more complicated and "open " than that .
Considering the millions of panels anything that might be shown to be a representation of the local environment is incredibly are ,despite regular attempts e.g. after last years excavation at Trefael we got this "it is now considered by several astronomers that the distribution of the cupmarks may represent a section of the night sky that includes the star constellations of Cassiopeia, Orion, Sirius and of course the North Star." Have a look at the amorphous groupings of cup marks and you might see that face in the cloud but you won’t find a representation of Orion (apart from the belt )which is everywhere ) That was a year ago and we have yet to see the graphic explanation , or even the names of the “astronomers “ . One bloke imagines the some of the markings of stones at Tara and the Boyne represents the monuments in their respective landscapes despite the scale being non –existent the same motif being used different types of monuments and the majority of the markings not having anything to represent . Have a look at the field notes for this ,he even makes up stuff without knowing where it is .http://www.themodernantiquarian.com/site/1274/east_tempar.html .
They are obviously communicative although the intended audience is unknown ,the more prominent examples could be considered to be directed at everyone including the gods and strangers whereas the more hidden ,in tombs , and on low lying more difficult to encounter unless you knew where they were examples , might not be for the stranger /uninitiated audience but even something as limited as the rock itself ,all could be apotropaic or simply decoration .Sorry better shut up or I’ll go on all day .