A XLANG/s compiler recognizes a statement in XLANG/s code to make an assumption as to the success or failure of a specified transaction. The assignment states of variables are tracked and changes to such states are recorded. While processing XLANG/s code, the compiler determines whether the assignment state of a particular correlation, operation or the like is correct for the transaction being performed. If not, the compiler may generate an error message. Moreover, by using declarative assumptions such as if(succeeded(T)) or if(!succeeded(T)), definite-assignment analysis of shared state variables may cross transactional boundaries.