Structure and evidence in identity cases

We present a framework for agent identity with a focus on structured cases and numerical levels of evidence and their handling. Our framework focuses on id-situations, where a person is judged to be the agent in some scenario, particularly a crime scene. An id-situation has a constellation of associated situations (providing what we call an id-case) to produce the objects used in it. Our idea of a situation is modeled on Barwise and Perry's situation theory. We represent our situations using semantic web notation because, for one thing, the semantic web supports a structure of partial information. From a numeric standpoint, we create a justification-based mass function from each id-situation and then combine the multiple functions we get from having multiple id-situations using Dempster-Shafer theory. The id-situations give a measure of similarity between each suspect involved and the as yet unknown criminal, which we adapt to get a mass function, with a frame of discernment that can be approximated as the list of suspects. We then refine our frame of discernment using constraints based on objects shared between the id-situation and its corresponding supporting situations.