"Work": development-work version with night builds for some numbers and specific (subscription to support) Linux distributions.
0.9+rNNNN, where "NNNN" — SVN (SubVersion) revision number.
"LTS" (Long Term Support): Formal and public release of last "Work" version, at releasing time, with support up to next iteration: "Work" -> "LTS" (zero update number), "Work"++.
"U" — Regular update number, 2-4 month. After the regular update period from "Work" version to "LTS" will be merging all fixes and improvements, also broken some API compatibility, but not broken the function and data compatibility, and U++.
"S" — Service update number. For any hot fixes automatic or manual (for specific) will be building service update (S++) version which allowed only for subscribed to official support consumers.
The page have addon documents, and links to it. To list of documents included materials about conferences, diploma project's materials, based on OpenSCADA, and other accompanied documentations. Documents page.