Ian Cartwright presents some of his work (developed with Martin Fowler) on Event Patterns, including: Event Sourcing, Event Collaboration, Parallel Model, and Retroactive Event. These patterns can be used in scenarios where a sequence of domain model changes may need to be recorded, reversed, corrected, or simply observed.
Domain Specific Languages (DSLs) are limited forms of computer language designed for a specific class of problems. In this JAOO conference talk, Martin Fowler introduces a simple example of DSL, bringing out the difference between external and internal DSLs, and talking through the trade-offs in using both forms. The talk is based on Martin's language workbench article on martinfowler.com.