A Method to Share Word Knowledge of Dependability Case

System developers should explain system errors sufficiently, during a system failure situation. This is an essential act in order to verify the dependability of systems. Dependability Case (D-Case) is one method for confirming systems of dependability suffciently, against a system failure situations. However, in D-Case, we could not clearly describe the relationship of words (people, objects, activities) within its (D-Case) nodes. For this reason, we introduce a new way to define Word Relationship Diagram (WRD) that describes the relationship of words within D-Case and propose our conversion rules from Dependability Case to Word Relationship Diagram (D2W rule) and vice versa (from Word Relationship Diagram to Dependability Case (D2W rule)). In addition to this, (1) we created a rule for the relationship of words for D-Case. (2) We applied the rules to the Dependability Case (D-Case) and the Word Relationship Diagram (WRD) of a train operation system.