Digital identity is the representation of identity in terms of digital information.
A digital identity can be understood as the set of digital information that is attributable to any given entity. This entity may be human (an individual or a community), a physical object, or even digital information itself.
Luke continues on to discuss how identity is the product of relationships, how it is used in authentication, how it relates to ontology – all in all an ambitious and thoughtful piece of work that people should look at.
I have to admit that I like the way he starts out, but prefer to separate the “evaluation of claims” (what Luke calls “attribution” based on “trust”) from the concept of digital identity itself. Otherwise things get way too complex.
I think it gets us much further in a practical sense to stick with the idea that a digital identity is simply a set of claims (assertions that are in doubt) made by one digital subject about another digital subject.
I argue that what an observer “makes” of such a set of claims is just another set of “claims”, this time made by the observer (they may or may not be conveyed further).
I hope all lovers of recursion will catch my drift.
You end up with a simple transform of what you started with – a set of claims made by one digital subject about another. Thus the matters of trust and attribution are at a higher level of abstraction than the mechanism for expressing identity.
This also makes it easier to build a system that works across boundaries but leaves the social issues of trust open to many possibile differentiated implementations.