AARTT

Founded in November of 2000, AARTT is a consortium of technology companies that have vowed to solve the technical challenges of interfacing the various systems involved in online real estate processes. The Alliance is working to bring its CRTML (comprehensive real estate transaction markup language) initiative to real estate technology providers as quickly as possible so that real estate professionals can soon reap the full benefits of online transaction management. rets + idx search from hit "[XML] standards in the real estate industry"

Seems more residential based ...