I have a college assignment to create an entity-relationship diagram (ERD) for a database we're going to build. That's fine, but I have to include something called an "Operational Master" in the ERD. The lecturer's description is vague at best, and I can't seem to find any info about it online.

Basically speaking, we have to create an ERD for a game rental service with at least one "operational master". The only other reference to it in the lecture notes was to "add an index for the 'operational master'". It was never really explained during the lecture as far as I can recall. I get what an index is, but not what is meant by the "operational master".

Has anyone any ideas on what this might be?

  • 2
    You might want to include more context and the lecturer's description, however vague it seems to you -- "operational master" could mean few hundred different things.
    – mustaccio
    Oct 24, 2017 at 15:25
  • 1
    Can you ask the lecturer? You could also talk to other students, to see if this is generally not understood, or if perhaps you missed something.
    – RDFozz
    Oct 24, 2017 at 16:26
  • Everyone else I've talked to is just as confused as I am, unfortunately. I fully intend to ask for clarification at our next lecture, but I have this assignment due tonight. Oct 24, 2017 at 16:48

1 Answer 1


You piqued my curiosity here. Cursory search on the internets mostly shows that this question haunts students since at least 2014, with no apparent relief. However, there seems to be one page that explains what an "operational master entity" is:

The key-only parent entity (otherwise known as an operational master entity, a collection entity, or a categorising entity, or perhaps a domain entity) stores the valid or actual range of values for the attribute.

A domain entity commonly translates to a dictionary, lookup, or dimension table. For example, for a Game entity a Publisher might be one operational master entity. The Publisher entity would have two attributes, a surrogate Id and Name.

P.S. It appears Google Books have a few more occurrences, mostly from the last century.

  • Wow, great sleuthing. I searched as well and promptly gave up. That page was created in 2010 but I wonder how archaic that term actually is. Oct 24, 2017 at 17:04
  • Great job finding all of this. So is this a type of table index or something completely different? Oct 24, 2017 at 18:40
  • I'm not sure if I can put it more clearly than I (and the sources) already did... An operational master entity (=domain entity) represents a set of valid domain values. For the Country domain it would be a set of country names. For the GamePlatform domain it would be a set of possible game console types.
    – mustaccio
    Oct 24, 2017 at 19:24

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