Tagged data-modelling
3 pieces
- · 10 min read
Entries Are the Record, the Balance Is a View
A balance held in a column is a cache with no source behind it. Every correction becomes an edit, and nothing in the system can reconstruct how the number reached its current value. Derive the balance from entries instead and it is explainable at any date, while corrections become entries rather than edits. The cost is real: derivation is slower than reading a column, and a stored snapshot is an optimisation of the derivation rather than a replacement for it.
- · 10 min read
Year-End Is a Rule, Not a Reset
Carry-over, expiry and lapse at a period boundary are derivation rules applied at a date. Implemented as a destructive reset that overwrites the previous period's state, the previous year becomes unreconstructable and any retrospective correction is impossible. The reset version is always the one chosen first, because it is a smaller piece of code and the cost only appears months later when somebody asks a question the system can no longer answer.
- · 10 min read
Positions, Not Stock Levels: What Changes When the Operator Is the Counterparty
An operator who buys and sells on their own book is not an intermediary moving other people's goods. What they hold is exposure, and exposure is not a quantity. A warehouse model tracking units in and units out loses the exposure view entirely, and turns a reallocation into an untraceable edit to two numbers. Modelling positions explicitly, with allocation and reallocation recorded as transitions, lets the book explain itself.