Complex sentence: JSON Schema was proposed by the Internet Engineering Task Force (IETF) but was allowed to expire in 2013 and thus is less mature and a riskier alternative to XSD, the most recent version of which was approved by the W3C in 2012.
Split into simpler sentences: JSON Schema was proposed by the Internet Engineering Task Force (IETF). It was allowed to expire in 2013 and thus is less mature and a riskier alternative to XSD, the most recent version of which was approved by the W3C in 2012.