I have a lot of information about the Pick system. I worked on the system from 1976 onward at Microdata. Moved to Irvine Computer Corp and worked on R77 and R80 which ran on Microdata and later Intertechnique hardware.
I can supply more information perhaps if you have a particular "flavor" or manufacturer. There were about 30 licensees of various systems.
The system is currently sold from Rocket Software as D3. The Microdata Reality system is now owned by NEC after a journey thru various owners, and is still separate from the Pick system Rocket has. Al of the Pick versions (Unidata, Universe) as well as the licensee's ended up at Rocket.
I will check and post a followup here with more general information for the thread when I can find it.
Reality
Reality, the original NoSQL, MultiValue Database SQL enabled for interoperability
reality.necsws.com
Rocket D3
Rocket D3 is the business application development tool that allows to easily create powerful applications for your business with the performance and speed you need to compete.
www.rocketsoftware.com
Also note in the D3 url the term "multivalue". This term was adapted for the Pick type databases and generally is used in references to Pick type systems or subjects.
Pick stores data with a 3 level hierarchy level of data fields, attributes are akin to fields on other databases. Values are contained in attributes, and can be as many as you desire. Subvalue fields are less used, but are contained in values. I know this is a bit vague, just adding to help point you at where "value" comes from in "multivalue".
The hackaday folks have this info about Pick. The book was written by my late friend Jon Sisk, and if you look for his books they are very informative.
We usually at least recognize old computer hardware and software names. But [Asianometry] taught us a new one: Pick OS. This 1960s-era system was sort of a database and sort of an operating system …
hackaday.com