Business logic errors occur when a user violates an application rule or enters a situation the rules did not anticipate. Treat them as expected failure paths: guide the user, explain the constraint, and provide a route forward instead of exposing technical details. section 7.1.1 section 7.3
Common business-rule violations include:
- Submitting invalid form input. section 7.1.1
- Applying an expired discount code. section 7.1.1
- Uploading an unsupported file format or an unexpectedly large image. section 7.1.1
- Registering an email address that already exists. section 7.1.1
- Exceeding the permitted number of login attempts. section 7.1.1
Design the failure path
An unanticipated user action should not lead to an infinite spinner or an incomprehensible stack trace. Validate and reject invalid requests early, communicate what happened in understandable terms, and help the user complete the intended process. Keep raw implementation details behind the application boundary. section 7.1.1 section 7.3
Table 7.1 Summary of failure types and handling strategies
|
Type of failure
|
Description
|
|---|---|
|
Business logic errors
|
Violations of business rules or expected usage constraints that the system must anticipate and communicate clearly
|
|
Technical problems
|
Failures caused by external systems, infrastructure, configuration, or unavailable technical dependencies
|
|
Programming errors
|
Defects in the code itself caused by incorrect logic, invalid assumptions, or broken invariants
|
|
Fatal errors
|
Critical runtime failures that compromise process stability and usually prevent normal recovery
|
Compare business logic errors with technical problems, programming errors, and fatal errors to choose an appropriate response. section 7.1.4
