Consider how one would represent the following image in vector graphics:
Pretty simple, right? The entire shape can be represented by a single path element.
But suppose additionally that you want to color the heart at the top red. The path element is an open shape, so trying to fill it results in an appropriately red heart but also implementation-dependent bleeding between the spiral endpoints.
Obviously, one could just draw the heart and the spiral tails as separate elements, but then the vector graphics representation no longer mirrors how a human being would draw the same image, and makes it more difficult to manipulate as a single object. One needs a way to communicate to the computer that two particular path segments within the larger path intersect in such a manner that they close a sub-shape.
Is there a vector graphics format capable of doing this? More relevantly, how is it implemented and are there any papers on it?