Johannes Ernst has blogged about my email to him concerning his blog on modeling identity data. I pointed out that in his original post he said he was modeling his business card but what he actually modeled were complex relationships not contained on a business card. His reply has three main points, and I will bite.

Back to Pete’s comment. The real-world, hard-paper business card also clearly shows the limits of what can be done with it:

  • Many times, I meet people who give me more than one business card, because they are affiliated with more than one business, and the only way this situation can be handled is through multiple business cards. When I get home and try to put the business cards away in my rolodex (which is ordered by company, not by name), I have to separate those two cards and the relationship “the same person gave those to me” is lost, which is unfortunate and which is something I wouldn’t want to permeate in the electronic universe.

These issues are a function of the physical limitations of the business card. We are discussing digital identity where such limitations, if imposed, are artificial. Unique identifiers are all that is required to ensure that I know two sets of information refer to the same entity. It is a rare unique identifier indeed that cannot be stored in a name value pair, and an even rarer one that a set of name value pairs are insufficient.

  • Some people cram lots of other information on the card, like their particular expertise, awards they got, the slogan of their employer, a picture, the (one, two or more) blogs they are running etc. While one can argue whether the business card is the place where this information should be, it’s clear that some people feel very constrained by the format that such a card can have and they would like to point to other information they consider relevant for receivers of the card. (Which is related to the case why using one’s blog as an identity is often such an appealing solution.)

So people want to share their information and what information they wish to share is determined by context. Not seeing an argument against name value pairs here.

  • It is also clear that business cards are not good at all for conveying some of the newer kinds of identity information that people want to convey in identity transactions. Dick Hardt, for example, would like to exchange only his list of favorite books in some identity exchanges. I would like to be able to selectively expose my social network etc. etc. In the physical world, we’d struggle to convey that kind of information on a business card because we’d have to have a lot of meta-data and description around it that would help receivers to understand what all of this information means. Which is of course exactly my point about needing semantic richness and before that, a more powerful representation scheme than name-value pairs.

It really isn’t clear at all to me why Dick Hardt can’t store his list of books in name value pairs, it is a list. Now, without conflating real world - digital world issues I would really like to know what the magic pixie dust is that conveys semantic richness upon XML et al without also having the same effect on name value pairs. Higher intrinsic expressiveness I will grant (along with additional complexity) - but semantic richness? It really doesn’t matter how Dick stores his book list, in order to make sense of it I will have to know what it is and how to work with it. And by the way, the computer will be doing that work.

In any case, let’s not model business cards. I want to see a real case that plausibly knocks name value pairs out of the solution matrix for identity data - not because I don’t think it exists, but because I believe ramping up the complexity requires real justification.