This might be like what you re looking for: dbpedia.org. They re working on extracting data from Wikipedia, and encoding it in a structured format using RDF, so that it can be queried using SPARQL.

Linkeddata.org has a big list of RDF data sets.

It s not quite what you re looking for, but Semantic Mediawiki adds database-like features to MediaWiki:

http://semantic-mediawiki.org/wiki/Semantic_MediaWiki

It s still fundamentally a Wiki, but you can add semantic tags to pages ([[foo::bar]] [[baz::1000]]) and then do database-type queries across them: SELECT baz FROM pages WHERE foo=bar would be {{#ask: [[foo::bar]] | ?baz}}. There is even an embryonic SPARQL implementation for pseudo-SQL queries.

OK this question is old, but Google led me here, so for anyone else out there looking for a wiki for structured data: Take a look at Foswiki.

Do you mean something like http://www.freebase.com?

You should check out https://www.wikidata.org/wiki/Wikidata:Main_Page which is a bit different but still may be of interest.

Something that might come close to your requirements is Google Docs.

What s offered is document editing roughly similar to MS Word, and spreadsheets roughly similar to Excel. I m thinking of the latter, of course.

In Google Docs, You can create spreadsheets for free; being spreadsheets, they naturally have a row-and-column structure similar to a database, and which you can define flexibly. You can also share these sheets with other people. This seems to be a by-invite-only process rather than open-to-all, but there may be other possibilities I m not aware of, or that level of sharing might be enough for you in any case.

mindtouch should be able to do it. It s rather easy to get data in / out. (for example: it s trivial to aggregate all the IP s for servers into one table).

I pretty much use it as a DB in the wiki itself (pages have tables, key/value..inheritance, templates, etc...) but you can also interface with the API, write dekiscript, grab the XML...

I like this idea. I have heard of some sites that are trying to pull together large datasets for various things for open consumption, but none that would allow a wiki feel.

You could start with something as simple as an installation of phpMyAdmin with a known password that would allow people to log in, create a database, edit data and query from any other site on the web.

It might suffer from more accuracy problems than wikipedia though.

OpenRecord, development of which seems to have halted in 2008, seems to approach this. It is a structured wiki in which pages are views on the data. Unlike RDBMSes it is loosely typed - the system tries to make a best guess about what data you entered, but defaults to text when it cannot guess. Schemas appear to have been implied.

http://openrecord.org

An example of the typing that is given is that of a date. If you enter 2008 in a record, the system interprets this as a date. If you enter unknown however, the system allows that as well.

Perhaps you might be interested in Couch DB:

Apache CouchDB is a document-oriented database that can be queried and indexed in a MapReduce fashion using JavaScript. CouchDB also offers incremental replication with bi-directional conflict detection and resolution.

I m working on an Open Source PHP / Symfony / PostgreSQL app that does this.

It allows multiple projects, each project can have multiple directories, each directory has a defined field structure. Admins set all this up.

Then members of the public can suggest new records, edit or report existing ones. All this is moderated and versioned.

It s early days yet but it basically works and is already in real world use in several projects.

Future plans already in progress include tools to help keep the data up to date, better searching/querying and field types that allow translations of content between languages.

There is more at http://www.directoki.org/

I m surprised that nobody has mentioned Wikibase yet, which is the software that powers Wikidata.