# Reads and writes

How a program reads and changes stored records: named queries, filters,
order and pages, totals, related records, the operations every entity
gets, what a refused write reports, and how an action stays
all-or-nothing while other requests change the same records. Where
records are stored, and how caches copy them, is on [Data](data.md);
who may read or change them is on [Policy](policy.md).

The examples follow the golden todo app's `planning` domain: `User`,
`Project` and `Todo`. Each example marked `check` compiles with this
checkout's `jadpo`, and its tests run against PostgreSQL. What isn't built
yet is listed in [What is built](reads-and-writes-built.md).