They are all template-specific “streamlined” things, I belive TD… = Template Data…
- TDS …Schema (XML schema)
- TDD …Document (xml instances adhering to a TDS)
- TDO …Object(s) (Class definitions, used for simplifying programming applications & integrations)
The template specific “streamlined” OpenAPI descriptions discussed in this thread could be used to produce the equivalent of TDO in any programming language (I believe TDO from the back then was usually in some .NET format)
@heath.frankel is likely the main guru on the topic and was involved in creating TDS/TDD/TDO formats many years ago at Ocean Informatics (now called https://oceanhealthsystems.com/). I believe many of the reasons for their creation were basically the same as the ones @ToStupidForOpenEHR brought up and that started this thread - to make it easier for developers and others to, for a specific use case, integrate/interact with openEHR systems - using familiar tools and without a learing too much about openEHR or openEHR specific tools.
When searching for TDS in the old openEHR mailing list archives you’ll find a lot of the same thoughts as in the current discussion, e.g. in 2008 and 2013. I believe the main problem regarding adoption was that the TDS/TDD approach was never published as an official specification back then - it was used by Ocean and some of their customers (including Better/Marand for example).
In 2016-2017 things had changed and there was a willingness from Ocean to share/publish the approach and create a specification, work was started, see the wiki page https://openehr.atlassian.net/wiki/spaces/spec/pages/30408770/Template+Data+Schema+TDS+Specification+and+associated+Template+Data+Document+TDD but never finished because of peoples’ busy schedules. Heath (who was very busy then) sent me some files that I (also busy) never got around to analyze and publish on that wiki page as a basis for further standardisation work. Perhaps it is time to pick that up again and let anybody interested help documenting the approach? @heath.frankel could you attach any files/descriptions for curious people to look at - on that wikipage or in this thread?
Others may have more information and links about TDS/TDD/TDO, please share. @Seref may know of current use at Ocean.