I've been thinking about cheap ways we might have UI for user-defined attributes in 0.7

What if we just had a single field in the detail view called that was a type-over-text field the way that the "Title" and "Location" fields are currently.

The "hint in grey" in this field might say something like Labels.

When the user clicks into the Labels field, they can either type just keyword-style tags: Mt. Olympus, Reviews, Vacation OR

They might specify attributes: Project: Reviews, Topic: Mt. Olympus

So the Labels field for an item might look something a hodgepodge of tags and "attribute:attribute value" pairings. Project: Reviews, Research, Topic: Mt. Olympus, Contact: Susan R., Guides, Vacation

This is pretty much what some people already do with tag-based systems like Delicious and Flickr. The bonus with Chandler is that we might actually be able to recognize "Project: Review" as a user-defined addition to the schema, rather than just another tag.

It would be nice if we could "grey-out" the attribute names to improve readability: Project: Reviews, Research, Topic: Mt. Olympus, Contact: Susan R., Guides, Vacation

We might also allow people to take an existing tag, and assign an attribute to it, after the fact: Project: Reviews, Research, Topic: Mt. Olympus, Contact: Susan R., Guides, Trip type: Vacation

This might allow users to add a lot of tags and custom attributes to items without having to solve the problem of "Where would they all fit in the detail view!" right away.

Auto-complete would be nice to have, but not a necessity for an experimental UI such as this.