Vertical XML Schemas

Copyright 2004-1016 by Ronald Bourret

In 2004, for reasons I no longer remember, I became curious about how many publicly available vertical XML Schemas were actually being used. To that end, I spent two evenings poking around the Web with a non-DSL modem (remember those?) looking for schemas that appeared to be active. In that time, I found ~100 schemas that fit my criteria: (a) a date of 2003 or 2004 associated with the schema and (b) apparent backing from a semi-reputable organization.

I conducted my research on five main platforms:

• The XML Cover Pages. These listed 500+ schemas, but most appeared to have died. A flurry of good intention from 1999-2001 didn't produce much.

• xml.org's Schema Registry (now unavailable). Like the XML Cover Pages, many schemas were clearly abandoned.

• Barry & Associates. Somewhat better than the XML Cover Pages and xml.org.

• OASIS. Hard to get a read on. Some projects looked real and others appeared to consist of nothing more than enthusiasm.

• Google. Searches of the form "<industry-name> xml", such as "airline xml", returned surprisingly good results, with most turning up something of substance.

Based on this survey, I guessed that 100 vertical schemas actually being used was a low-end figure.

• At least 75% of the schemas I found appeared to be being used.
• The definition of "schema" is very fuzzy. Many schemas I found were actually multiple schemas, such as HL7, OTA, and the UK government. Counting these individually would easily exceed 200 schemas. (Actually, the Danish government had more than 1500 schemas. However, many were small and clearly designed for modular use.)
• My search was minimal. I checked ~30 schemas on the XML Cover Pages, about 25% of the schemas on xml.org, and less than 10 industry areas on Google out of ~40 I could think of.

Based on this minimal research, I guesstimated I had found 1/4-1/2 of all active, publicly available, vertical schemas. I was optimistic because (a) many of the Cover Pages schemas were clearly failures or pet projects and (b) most industry searches didn't turn up more than a few schemas. (I did not include product-specific or privately-used schemas, of which there were certainly thousands.)

As of this writing (2016), it's safe to say that many of these schemas are no longer being used. However, a quick peek at the Web showed a surprising number were still active. And this didn't include just mainline schemas like HL7, DITA, METS, and SVG. It included schemas likely to be known only to people whose light reading consists of trade journals -- schemas like OTA (Open Travel Alliance), PIDX (Petroleum Industry Data Exchange), SportsML, and MISMO (Mortgage Industry Standards Maintenance Organization). Maybe the XML revolution happened after all.

The Schemas

NOTE: The links have not been checked since 2004, so many are likely to be out of date, even if the schemas are still being used.