Sorry for the duplicate response, but wanted to share "where to find the info" info with everyone. I am sure someone else on the list may have additional input, but here is mine: I did a bit of research and RetWall was part of the original 1.0 schema. Items added after that are better documented in the cumulative changes doc, but the original 1.0 was 11 years ago. In general, good places to look for info: 1. The LandXML.org mail list archive at //www.freelists.org/archives/landxml, goes back to 2001. 2. In the schema file itself, contains lots of notes: http://www.landxml.org/schema/LandXML-1.2/LandXML-1.2.xsd 3. The schema documentation files in : http://www.landxml.org/schema/LandXML-1.2/Cumulative%20LandXML-1.2%20Changes .doc http://www.landxml.org/schema/LandXML-1.2/LandXML-1.2%20Documentation.zip Out of 5,000 LandXML files from all over the world, I found one that has a <RetWall> element. Why? - it is part of a DTM surface definition source data. Pnts and Breaklines are common, if the source data is specified - but this is rare. A while after 1.0 was finalized, practical applications simply imported the DTM as triangulated. This insured the import would have the exact surface created by the other app providing the user a consistent experience. Of course we figured that out after 1.0 was finalized. To provide the best forward/backward compatibility, I don't delete or rename elements from the schema. That policy has worked out very well, but with group wide consensus I have renamed 1 element in 12 years (it just did not make sense). Best Regards, Nathan Crews www.landxml.org