Abstract: A queue data structure is stored on a computer-readable medium to represent a queue or list. The data structure includes a head pointer that points to the last or most recent list element to have been removed from the queue, and a tail pointer that points to the most recently added list element in the queue. The head pointer and tail pointer may be implemented as separate objects. The queue data structure is applicable to computer arts such as transactional database management. The queue data structure can prevent concurrency conflicts that could otherwise occur when an object modified in one transaction (e.g. by one user) is modified by another concurrent transaction (e.g. by another user).