Most web-pages comprise images, text and tables. We have specialist searches for images and text but no search targets tables.
Tabular data is handled by text search engines but only as discrete entries - it cannot be queried in terms of the underlying meaning.
A search engine capable of indexing
tables with their column headings, captions and general page context should allow for on-the-fly collation of data with matching descriptors from varying sources with a ranking for how related the data appears to be.
For example - a search for "Names of Kings and Queens of England by Year" might be able to combine data from a number of sources, with matching records building faith in the existing records, and misfitting records shown as 'dubious' but linked to their source.
Such a system would enable journalists, students and even scientists to quickly pull in numerical and other tabulated data on a topic, saving hours of search. The inclusion of tables from scientific papers would be the icing on the cake.
Edit - this is nothing to do with meta tags - it is to do with crawling and indexing content in <table>s