WALS is a large database of structural (phonological, grammatical, lexical) properties of languages gathered from descriptive materials (such as reference grammars) by a team of more than 40 authors (many of them the leading authorities on the subject).
WALS consists of a number of maps with accompanying texts on diverse features (such as vowel inventory size, noun-genitive order, passive constructions, and "hand"/"arm" polysemy), each of which is the responsibility of a single author (or team of authors). Each map shows between 120 and 1370 languages, each language being represented by a symbol, and different symbols showing different values of the feature.