I finally got my thoughts about Marco's metadata problem into words. I can sleep now, but I should get back to modeling search GUIs for Nautilus.

The three fates of Greek mythology governed the thread of life and wove it into a cloth representing a person's actions and relations.  Sutra is a Sanskrit word meaning thread, or connective cord, it shares the same root as suture, and it means a narrative.  The Sutra metadata database provides the means for users to store, organize, retrieve relevant personal data.  The data will change with every use,  strengthening and weakening its relationships to reflect the user's life.

Sutra has the attributes of several kinds of applications including directory servers, PIM apps, customization and state data, personalization service, and search engine.  It broadens the features of applications like Dashboard and Medusa, and offers new facilities to applications like Epiphany, Rhythmbox, GThumb.  It can extend and alter the development of applications like Evolution, or the Desktop.  It does not store the files or resources that the data pertains to, not does it offer utility to a group of users.  Few users will know that Sutra exists, but their applications will use it, and act as a proxy for the user.

You can read the full article if your interested.