Integration Choices: Interactive vs. Non-Interactive

A colleague of mine had a question on when a user interface (UI) would need to be provided to invoke a business service vs. using a database trigger to do the same. According to me,

• When the business pattern is Self Service i.e. the user wants to query the status of an order or place a claim (interactive), a UI would be most appropriate. In other words, whenever there is an interaction between a user and a system/application.
• When the business pattern is Application Integration i.e. synchronization between multiple databases or legacy systems or batch driven updates (non-interactive), a database trigger could be chosen. In simpler terms, whenever there is interaction among applications/systems rather than users and applications.