As a newcomer to the real estate industry due to the popularity of WP-Property, it was not long before I started hearing new acronyms - RETS, MLS, and IDX. From my experience working with numerous web consultants, who also found out about RETS when a client has asked them, I’ve realized that there is a general sense of confusion about the premise, so I decided to get involved in the topic and learn as much about is as possible - and share my findings, hopefully helping some other people who are confused and frustrated by this enigma.
First, the reason you are probably confused, is there are generally very few standards. Real Estate Transaction Standard (RETS), is somewhat deceiving - there are different versions, and different MLSs have different configurations. There are several RETS versions used: 1.5, 1.7, 1.7.2, 1.8 and 2.0
Mind that each RETS server is different, but they have one thing in common: They separate properties by category.