Organize business logic by operation, with each procedure handling one request.

Represent business concepts, rules, and relationships with behavior-rich objects.

Use one object to hold the domain logic for all rows in a table or view.

Define the application boundary and coordinate operations, transactions, and responses.

Centralize SQL and persistence operations for a table or view in one gateway.

Wrap one database row with fields and persistence operations.

Combine a record-shaped domain object with operations that persist it.

Transfer data between independent domain objects and a data source.

Present persistence as a domain-oriented collection of aggregates.

Track loaded and changed objects, then coordinate their writes as one transaction.

Ensure each stored identity maps to one in-memory object per unit of work.

Defer loading data until a consumer actually needs it.

Bundle serializable data for transfer across process or layer boundaries.

Allow concurrent work, then reject a write if the stored version changed.

Separate domain state, its visual representation, and input coordination.

Use one controller for a page, route, or closely related action.

Send requests through one handler for shared policy and dispatch.

Render output by combining a template with supplied data.

Centralize application flow and screen or command selection.