What kind of data structures are these? Can someone please point out any links or books where I can read more about them.
An explanation can be found in the paper titled "Recognition of shapes by morphological attributed relational graphs", in the beginning of section "3 Generating the attributed relational graph"
In addition, Doxygen doc on an implementation can be found here:
You can also check out this paper. From DVK's answer and that link, it sounds like they're normal graphs, but with "attributes" on the nodes and edges. For example, if you were trying to build an image processor, you might initially construct a graph where each node represents a distinctly colored region (say, a person's face vs. their shirt) and then edges represent visual adjacency (likely, a person's head/neck is adjacent to both their shirt and the background of the image).
Then, you would assign attributes to the graph elements. The attribute for each region (node) could be its predominant color, and the attribute for each edge would be how much of their circumference the respective regions share.
As a different example, you a colored graph with edge weights is a simple example of an attributed graph.
Perhaps I could be more helpful with a little more information about why you're looking into ARGs, since they're defined pretty generally.