Barr v. Resolution Trust Corp
In Barr v. Resolution Trust Corp., 837 S.W.2d 627 (Tex. 1992), the supreme court "reaffirmed" the transactional approach to res judicata, which relates to what claims could have been litigated in a prior lawsuit. See 837 S.W.2d at 631.
Under the transactional approach, res judicata may apply if the subsequent suit arises out of the same subject matter as a previous suit and, through the exercise of diligence, could have been litigated in the previous suit. See id.
A determination of what constitutes the subject matter of a suit requires an examination of the factual basis of the claims without regard to the form of action. See id. at 630.