Recognizing Actor Boundaries Through Domain-Driven Design: Lessons from a Shared WorkLog

When designing business-critical systems in Rails, we often begin with clear and concrete concepts. A model like WorkLog—which records completed work tasks—can seem straightforward at first. However, applying Domain-Driven Design (DDD), particularly Actor Analysis, can uncover subtle complexities that have significant architectural implications.

A Case of Overlapping Concerns

In a recent project, a WorkLog model was implemented to track task completions. At a glance, the model served a singular purpose: record work performed by employees. However, Actor Analysis revealed that two distinct groups interacted with this data in markedly different ways:

• Workers needed to log their tasks quickly and occasionally update entries as corrections arose during the workday.

• Quality Checkers, on the other hand, reviewed the same WorkLog data to ensure compliance with internal standards and external regulations. For them, the integrity and immutability of completed entries were critical.

While both groups belong to the same organization, their interaction with the data reflected differing priorities and expectations. Workers viewed WorkLog entries as flexible records of ongoing activity; Quality Checkers treated them as finalized reports requiring auditability and traceability.

Implications for Design

This discovery served as an important indicator: when different actors relate to the same data with conflicting expectations, special attention must be paid to workflow boundaries and data ownership.

In this case, a single WorkLog model was insufficient. The design evolved in the following ways:

• Introduction of a WorkLogDraft model: Workers interacted with drafts, which they could freely modify throughout the day.

• Promotion to a finalized WorkLog entry: Once submitted, drafts were transformed into immutable WorkLog records, which were the only entries visible to Quality Checkers.

• Separated responsibilities in the interface and application logic: Workers and Quality Checkers operated in different UI contexts, with distinct permissions, terminology, and views appropriate to their role.

This separation ensures clarity, reduces friction between teams, and enables better enforcement of business rules appropriate to each context.

Conclusion

Domain-Driven Design encourages developers to align software boundaries with the real-world domain. Actor Analysis, in particular, can reveal when a single data model is serving multiple, potentially conflicting needs. Recognizing these situations early allows for better modeling decisions—ones that respect the distinct goals and mental models of each actor involved.

In Rails applications, it’s tempting to lean on a single model to serve multiple use cases. But when subtle actor tensions arise, taking the time to delineate responsibilities through clear model separation and workflow design leads to more maintainable, accurate, and purpose-driven systems.