This topic is fascinating and I really hope the project takes off.
I'm a developing permaculturalist farming/growing on 11.3 acres of
land near my home. Planning to do my first
permaculture design course next month. In an earlier (part of my) life I did research into Mathematical Logic and taught in a computer science department for many years and I've been following progress on the Semantic Web for a long time. Only last night I installed a Semantic Media Wiki (SMW) on the servers I'm using for my websites, to get to grips with the technology and see if I can understand the issues and potential applications. I'm impressed, I must say, and my hunch is that this is the right way to go primarily because of the social and collaborative opportunities it presents and because of the great flexibility of the Semantic Web approach. I've worked with relational database (RDB) theory and technology and RDB management systems (RDBMS)s and with Drupal and Wordpress in the past so I've some
experience, if not a great deal of wisdom, in this area. There isn't an exact match within a SMW installation to a relational database (and the SMW people are aware of this and have their reasons) but there is a great match to other kinds of database (c.f. SPARQL and RDF stores,
http://semantic-mediawiki.org/wiki/Help:Using_SPARQL_and_RDF_stores ). One key point is that the structure of the database naturally evolves over time (as Berners-Lee anticipated many years ago when he proposed the Semantic Web) while this is much harder to accommodate in traditional RDMBSs. The structure is a collaborative effort (and can be edited wiki-style!) and doesn't require a developer to know in advance what works best. It also allows internationalisation so that permaculturalists speaking different languages (learning and using other languages is one of my favourite hobbies

) can still communicate effectively. And I expect
local dialects to develop and mirror the local climate and ecologies; using Semantic Web technology makes this all possible.
One thing I've observed is that old technologies seem better when I have lots experience of them yet new technologies are very seductive for people like me who mostly absorb positive reviews and the temptation to commit early to a particular technology, be it MySQL, Wordpress, Drupal or SMW, is very strong. And it does take someone to take an initiative even when the "best" approach isn't clear; it sounds as if Lawrence is doing this; I'm not clear if an alternative/complementary system is going to be developed out of this topic?
I'm very keen to learn more about local guilds and I'd be happy to contribute (in a relatively small way because of my other commitments) to this project if that turns out to be sensible. Whatever we do with our local
permaculture project (and we want to learn, understand and share a lot from it), it seems to make a lot of sense to make it easy to collaborate with existing projects rather than re-inventing the wheel ourselves.