User blog:Robin Patterson/Comment posted to TechnologyReview.com in reply to an article about SMW

Familypedia, a genealogy wiki, has been using Semantic MediaWiki, Semantic Forms, and Semantic Drilldown since mid-2009. Currently 180,000 total pages and growing at several hundred per week with only half a dozen really active volunteers and dozens of casuals adding ancestors.

When a user adds or edits a page about an individual, the data is in form fields, with the software creating or editing "facts" (a fact being a combination of a "property" and a value). A later query gets selected facts displayed in a chosen arrangement.

http://familypedia.wikia.com/wiki/Help:Semantic_MediaWiki/demo_query-range shows an example of the result. It lists all articles of people born in the 1500s that have images, tabulated with columns for image name, birth date, death date, father, mother, and "children by first marriage". Each column can be clicked to sort in predefined order, such as birth date. The site has over 900 "properties", most of which could form a column in such a table.

http://familypedia.wikia.com/wiki/Semantic_MediaWiki/demo_query-subquery lists all Familypedia people born in Pennsylvania whose father was stated to be born between 1849 and 1875. Handy if a surviving fragment of a letter from a great-aunt or great-uncle (without a name, just addressed to "My dear great-nephew") said "I was born in PA" and "Dad emigrated in 1875" and "his parents were married in 1849".

Any user of the wiki can construct such a search based on a combination of known facts.

When the site has millions of articles instead of just thousands, it will be even more useful if the software can handle the volumes. No big restrictions are foreseen. Such queries exploit the existing caching mechanisms of MediaWiki, so that most requests for a page with such dynamic contents can be served with little or no performance impact.