One Owner Per Fact

"Two authoritative copies of the same fact is not redundancy. It's a future argument about which one is right."

The Full Ownership Map

Zoom out to the whole family and the ownership map is crisp. Eagle owns the original reference images. Loomis owns the analysis and presentation state — fits, corrections, attempts, boards. Cinder owns the native, always-on-top shell. cwkPippa owns the brain: identity, conversation, routing, memory. Each system owns exactly one kind of thing, and that assignment is deliberate and non-overlapping. No two systems are the authority on the same fact.

Reference Across, Absorb Never

Because ownership is exclusive, everything else is a reference across the boundary. A Loomis session stores a typed pointer to its Eagle original — at minimum a (source_id, item_id) — alongside its own Loomis-owned analysis. It does not copy every Eagle original into a second media library, and it does not reach into Eagle to own the pixels. The reference crosses the boundary; the ownership stays put. You saw this exact move with reference boards; stated as doctrine, it's the rule every system obeys, not a one-off in the board feature.

The principle underneath is as general as software gets: every piece of data should have exactly one authoritative owner, and everyone else holds a reference to it. The moment a single fact has two owners — two places that both claim to be the source of truth — you've built a drift machine. They will disagree eventually, and then every reader faces the unanswerable question 'which one is right?' Single ownership makes that question impossible by construction: there is always exactly one answer, because there is always exactly one owner. It's the same instinct as database normalization and the 'single, authoritative representation' at the heart of DRY.

Why Doctrine, Not Just Convention

This rule is written down as doctrine — in the architecture document, not left as folklore — for a specific reason: it erodes silently under local pressure. 'Just copy the original in here, it's easier for this one feature' is always the tempting shortcut, and it's exactly the move that mints a second owner and seeds the eventual drift. A convention lives in people's heads and evaporates when they're busy; doctrine is written where the next contributor will read it before they take the shortcut. Making the ownership map explicit is what keeps a small convenience from quietly becoming a two-owner bug six months later.

Code

One owner per fact; everyone else holds a reference·python

# One owner per fact. Everyone else holds a REFERENCE across the boundary.
#   Eagle    owns  original image bytes
#   Loomis   owns  analysis + presentation state  -> refs Eagle by (source_id, item_id)
#   Cinder   owns  the native always-on-top shell -> refs a deep-linkable Loomis board
#   cwkPippa owns  identity / conversation / brain -> every surface binds, none forks it

# A Loomis session stores a TYPED reference -- never a second copy of the original:
session.source   = EagleRef(source_id="eagle", item_id="abc123")  # a pointer across
session.analysis = (fit, corrections, attempts, versions)         # Loomis-owned truth

# Copy the original bytes in here and you've minted a SECOND owner -> guaranteed drift,
# and the unanswerable question 'which copy is right?' the day they disagree.

Exercise

Find a fact in systems you use that has two authoritative owners — the same customer address stored in two databases, a config value duplicated in code and a dashboard, a number copied into two spreadsheets. Describe the drift it has caused or risks, then redesign it: which single system should own it, and how would the other become a reference that reads through instead of a second copy?

Hint

The tell is any fact you have to remember to update in more than one place. Pick the system with the strongest claim to own it (usually where it's created or most authoritative), make that the single owner, and convert every other copy into a live reference that reads from the owner. The drift disappears because there's no longer a second copy that can disagree — only one truth, referenced everywhere.

One Owner Per Fact

The Full Ownership Map

Reference Across, Absorb Never