On Isbell's density theorem for bitopological pointfree spaces I

Abstract This paper addresses dense sub-objects for point-free bitopology in terms of d-frames and provides several examples. We characterize extremal epimorphisms in d-frames and show that a smallest dense one always exists, establishing a proper analogue of Isbell's Density Theorem for d-frames. Further we explore certain questions about the functoriality of assigning the smallest dense sub-object to each pointfree bitopological space.