I think that this is interesting because it explicitly decouples they XPath query "API" to the weblog from the underlying storage mechanism. In Syncato, the XPath query API falls out because the underlying storage is XML oriented and provides XPath support (via some code that Kimbro wrote). The thing that seems to have captured people's imagination is the ability to use XPath (some other semistructured query language) to get information out of weblogs at a sub entry granularity. For ease of implementation, Syncato can't be beat (build and install issues aside). But Mark's approach shows that it's possible to get an XPath API to data that isn't stored natively as XML. Will it be more work? Yes. Will someone have to document a "schema" for that data? Probably. The one drawback is that the data in the weblog needs to have enough annotation so that the XPath queries can produce something meaningful. And that may be where things start to fall apart. In pyblosxom, we have entryparsers and preformatters that let you enter your blog posts in a variety of formats. Not all of these formats will have the annotations needed for an XPath engine to find meaningful information. That takes us back to the annotation conventions that Jon Udell was writing about a few weeks ago...