Lots of emails and a conversation with JJ, in which we decided on the following:

• I'll take a copy of the data to work on now; no further work will be done on it until the work can be done in a new version of the db. The PHP pages have not been changed in the past week, so I can keep the conversions of five of those that I've already done.
• We will abandon the use of the special index file INDEX1.xml, and instead create separate pages for each of the locations on the map. There are 677 such items in the index file, of which 98 correspond to existing files in /locations. This merging and file creation can be done with XSLT, and that will be my first task.
• DB indexing will be used to optimize access to the location data, so there should be no performance penalty from abandoning the index file.
• Markup problems will be resolved, partly manually and partly automatically; initially, the db will continue to support some oddities (such as the use of lg and l for layout) until they have been resolved manually.
• The experimental map will be brought down initially, and GN and I will work on a new implementation of it. The new version of the db will be launched initially without it, so that work can continue on it the data.
• Full markup documentation will be created during the conversion, along with templates and other instructions for markup folks.
• We aim to get the new app up and running in three weeks.