It’s a tough problem: if you do things (like scanning entire libraries) at Google-scale, you just can’t pay attention to the details. One partial way out (which Geoff mentions) is to allow users to submit corrections, as Google Maps does for positions of placemarks.

The article addresses a number of important points about the provenance and usefulness of metadata, and Google employees provide some great comments and discussion.

(Via Brad DeLong).

He names the two approaches “structure-and-browse” and “collect-and-query”. I feel like I’ve been groping for these terse descriptions for years!

Chris Anderson of The Long Tail has an important post about how the metadata used in some music-listening applications doesn’t satisfy the listeners needs:

[...] classical is a genre that the one-size-fits-all music aggregators such as iTunes don’t handle particularly well. They’re oriented around pop music, with its artist, album, track data format. Meanwhile classical music organizes around composer, conductor, performer, soloist

He also voices my exact peeve about how jazz is treated:

However, neither of them does a very good job with Jazz, where the individual musicians are often more meaningful than the band.

Yup. No reasonable cataloguer of jazz recordings separates “Thelonious Monk Trio” from “Thelonious Monk Quartet” from “Thelonious Monk”. At the same time, it’s important to be able to locate all appearances of Thelonious Monk, regardless of whether he was the leader of the session (note that “leader” and “session” are appropriate terms in jazz discography, but not for pop or classical).

When your only tool is a hammer…

I can’t help but wonder if the problems Chris calls out in iTunes come from the poor selection of data tools in most applications programmers’ toolkits. Relational databases, the current orthodox storage technique, favor using one or more tables, each consisting of records having the same selection of attributes. There are hacks you can use to simulate having, say, jazz tracks and pop tracks in the same Tracks relation, but hacks and simulations tend to twist one’s code, so most programmers resist going there.

An XML database in every toolbox!

We don’t really have to live this way anymore. With the popularity of XML for data interchange, the tools ecology has given us a variety of XML database systems. The XML data model has the flexibility to represent varying record structures: in fact, it has much more flexibility than we need for the purpose!

Heretical as it may seem to put the cart of an interchange format before the horse of data abstraction, the XML situation is very useful in practice, at least for databases of moderate size. The W3C has come up with the XPath and XML Query specifications that provide excellent query mechanisms for data represented in the XML model. XML Query in particular is designed to look somewhat familiar to the hardened SQL user. There’s data typing taken from the XML Schema datatype recommendataion as well.

Better nails

Anyhow, let’s learn to design with a more flexible hammer, and maybe we’ll be able to hit a wider class of nails, rather than our users’ thumbs!

March is International Runaway Metaphor Month.

OpenStreetMap is a wiki-like project to build a world map using contributed GPS tracks [OpenGeoData pointed me there]. Their map of Baghdad is here.

This project is truly a product of the early 21st century: it requires GPS satellites, cheap but accurate GPS receivers, the World Wide Web, inexpensive computers with fast color graphics, and so forth.

And like all modern geographic applications, it also exploits a special property of GPS’s information domain: everyone agrees on the meaning of geographical location; only dates and times have a similar level of standardization. In relational-database terminology, this means that any table with a date or location column has a meaningful join with any other.

This doesn’t work with most data. I’ve had driver’s licenses in four U.S. states, but you can’t aggregate my driving record from the state records because they all use different ID numbering schemes (nice for my privacy in this case).

Also noteworthy is the fact that GPS information can be used to put a time dimension into maps, since we can tell when the street is used as well as where it is. There are some very pretty examples at Cabspotting.