context-propagation-spectrum

How much context you have in a system can greatly depend on the structure of your data.

context-propagation-spectrum#spectrum1

• No context
  • What happens?
    • In-place updates directly on the data
  • Outcome
    • When: No way to know. Things like updated_at are a bit of context-propagation, if they exist at the application code level, but direct updates to the database can make them problematic
    • Cause - Technical: No way to know.
    • Cause - Logical: No way to know.
    • Ease of understanding: Hard - need to read code, reason about when the code ran, find any existing logs which are separate from the data
• Minimal context
  • What happens?
    • In-place updates directly on the data with application-level audits
  • Outcome
    • When: Can understand when the update happened (if it was done through the application, not if done directly in database)
    • Cause - Technical: unknown unless propagated
    • the technical cause of it, the actual reasoning for it, etc.
    • Ease of understanding: TODO

... some more steps in here ...

• Maximal context
  • What happens?
    • The only system-of-record data that is persisted is systematically-enforced immutable facts
    • Coincident with those facts, additional propagated context is persisted
      • Potentially even from previous steps this step doesn't understand
      • Easily-queryable meta-info, such as reified transactions (#) (like what version of the code was running)
  • Outcome
    • When: Yes, you will know when the data was created, and it will never be accidentally changed after-the-fact
    • Cause - Technical: Associated change in the same transaction is captured, because the transaction is captured and has meta-information associated with it
    • Cause - Logical: The motivation for the change is captured, and you can join on the upstream changes to determine their motivation as well.
    • Ease of understanding: Easy. All the context is available, and effort has been put towards making it readily queryable

context-propagation-spectrum#spectrum1

Referring Pages