A DOI is useful feature to any electronic document. What the ID number in your passport is to you is the DOI to a document. It simply helps to make sure you address the “object” you want to address. Similarly, there may exists several “Joachims Zwiwwelkoecks” in this world (well, it may or may not be the case). However, if any of this person gets his (or her) unique ID (could by a simple number), then we would in principle always be certain that we address the right …