Journal · Short film
The Ship of Theseus is hiding in your customer list
An old paradox about identity, and the very practical question your database has to answer about every customer who changes.
Captions are on. The described version stops at each scene while a voice says what's on screen; that voice is synthetic, and the narration is ours. There's no sign-language version yet. The full transcript is below.
The paradox
Plutarch tells how the Athenians kept Theseus's ship for centuries, replacing each rotten plank with new timber. Philosophers used it as the standing example of a question with no settled answer: when every part has been replaced, is it still the same ship?
The database version
Meet Widget Co., a great customer. Then they rebrand: new name. They move across the state: new address. A bigger company buys them: new owner. Same customer?
Say yes, and five years of sales history stays in one place. Say no, and you get a second record. Search the old name and you find nothing: a ghost customer.
Sometimes no is the right answer. If the buyer folds them into a different legal entity with its own tax ID, merging the two records can put the wrong name on an invoice.
If nobody decides, someone just clicks new customer. Do that enough times and one customer is wearing six name tags, and no report can see they're one. That's one way duplicate records happen. It isn't carelessness. It's a question nobody had time to answer.
What this doesn't prove
That there's a universal rule. There isn't.
Pick a rule, write it down, and use it every single time. The right rule depends on what you need the record to do.
Transcript
Narration as spoken, with what's on screen described in the indented lines. Company names and amounts in the film are made up.
Your customer list has a philosophy problem. It's called the Ship of Theseus. Replace a ship's planks one at a time until none of the original wood is left from the original ship. Is that still the same ship? Philosophers have argued about that for around 2,000 years. Your database has to answer it by next Tuesday.
On screen: A made-up customer record. Name changes from Widget Co. to Widgetry, the address from 14 Mill Road to 220 Harbor Ave, and the owner from Independent to Big Parent Group.
Meet Widget Co. Great customer. Then they rebrand. New name. Then they move across the state to a new address. Then a bigger company buys them. New name. New address. New owner.
On screen: Same customer? The record splits into two cards. Merged, it keeps 5 years of orders in one record. Split, the new record has 0 orders, and searching the old name finds no orders: a ghost customer.
Same customer? Say yes and five years of sales history stays in one place. Say no and you get a second record. Search the old name. Find nothing. Ghost customer. Uh-oh. And sometimes no is the right answer. If the buyer folds them into a different legal entity with its own tax ID, merging the two can put the wrong name on an invoice. That's a fun phone call. If nobody decides, someone just clicks new customer.
On screen: Six customer cards with variant names of the same made-up company fan out. No report can see they're one.
Do that enough times and one customer is wearing six name tags and no report can see it and we don't know who they are anymore. That's one way duplicate records can happen. It's not carelessness. An unanswered question that we don't have the time to answer. The paradox has no right answer. Your database needs one though.
On screen: Card: What this doesn't prove. That there's a universal rule. There isn't. Pick one. Write it down.
Pick a rule, write it down, and use it every single time. There's no universal rule.
On screen: Text: The right rule depends on what you need the record to do.
On screen: End card: the Highland Willow willow-tree logo grows from its trunk and roots into its canopy, then the words Highland Willow, highlandwillow.com/journal, and We publish our working.
Sources
- Plutarch. Life of Theseus, 23.1.
Narrated and produced by Highland Willow. The audio-description voice is synthetic (macOS text-to-speech). The animation is drawn in code. None of the film's data comes from any client.