The many meanings of metadata

As we weave more and better metadata into software, documents, Web sites, and file systems, the information stored in these various containers will become more available, more cohesive, and therefore more useful. The next challenge is how -- in this new era of interconnected systems, people, and business processes -- to unite these separate realms.

The solution is a complex recipe, but we can find many of the ingredients at work in the emerging discipline of SOA (service-oriented architecture). We use metadata to describe the interfaces to services and to define the policies that govern them. The messages exchanged among services carry metadata that interacts with those policies to enable dynamic behavior and that defines the contexts in which business transactions occur. The documents that are contained in those messages and that represent those transactions will themselves also be described by metadata.

There's no overarching schema for the metadata that flows through the service network, touching routers, registries, security gateways, databases, and end-user applications. And, in view of its many forms and uses, it's not clear that convergence on a single standard is necessary or even desirable. What is necessary is that within each metadata domain we strike healthy balances between the constraints we apply to metadata vocabularies and the evolutionary freedom we allow them. Across domains, we'll speak the lingua franca of data and metadata, namely XML. [Full story at]

I very much enjoyed writing this feature story on several of metadata's many faces. When it showed up at, I couldn't help but notice this:

TAGS: .net Flickr filesystem java metadata owl rdf semantic tagging web winfs xml

The See Also items are tag-related, but weakly -- through the tags web and java. I can see a couple of ways to extract more value from this metadata. As an exercise, I gathered the contents of the buckets for the set of tags applied by InfoWorld's account. Then I added items from the corresponding buckets in my own account.

One useful heuristic is to look for items that have been bookmarked by other users, which is an automatic measure of interestingness. Another is to notice that a tag which also occurs in the title of an article is likely the most important tag. Applying these two rules gave me this list:


Jon Udell: Meta-mail 19
Jon Udell: Collaborative knowledge gardening 15
Jon Udell: Enhancing search results with metadata 12
Jon Udell: Audio linkblogging 2


Tag mania sweeps the Web 92
Jon Udell: A progress report on InfoWorld's experiment 33
Jon Udell: Social tagging in the enterprise 18


Jon Udell: The social imperative 9
WinFS and social information management 3

Automating that procedure looks like a fruitful exercise. Of course there's always More Than One Way To Do It. A Google search for infoworld metadata finds this week's feature story first, and Mining message metadata -- which predates the tagging craze -- second.

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