Andrew asked for per-UDDI-category queries for the OPML lists my little tool creates and here it is:

Optional query parameters:

scheme=<<name of one of the pre-registered categorization schemes in the Microsoft UDDI registry>>
key=<<a key from a category>> (required parameter if scheme is provided)

For the following categorization entry for a service in UDDI (one of the RSS tModels is required in addition to that):

Categorization Scheme: ntis-gov:naics:1997
Key Name: Information Services and Data Processing Services
Key Value: 514

the proper query is therefore