methods of organizing a series of sibling data entities in a digital computer are provided for preserving sibling ranking information associated with the sibling data entities and for attaching the sibling ranking information to a joint parent of the sibling data entities to facilitate on - demand generation of ranked parent candidates . a rollup function of the present invention builds a rollup matrix that embodies information about the sibling entities and the sibling ranking information and provides a method for reading out the ranked parent candidates from the rollup matrix in order of their parent confidences . parent confidences are based on the sibling ranking information , either alone or in combination with n - gram dictionary ranking or other ranking information .