The knowledge-based system TERSEO was originally developed for the recognition and normalization of temporal expressions in Spanish and then extended to other languages: to English first, through the automatic translation of the temporal expressions, and then to Italian, applying a porting process where the automatic translation of the rules was combined with the extraction of expressions from an annotated corpus. In this paper we present a new automatic porting procedure, where resolution rules are automatically assigned to the temporal expressions that have been acquired in a new language, thus eliminating the need for automatic translation and consequently minimizing the errors produced. This is achieved by exploiting the rules of the temporal model, which are language independent, and the information extracted from the annotated corpus. Evaluation results of the updated version of TERSEO for English show a considerable improvement in recognition performance (+ 14% F-measure) with respect to the original system

The paper investigates several properties of binary trees related to the position of the elements in the permutations generating the trees. The properties are studied using ‘leaf analysis’, i.e. deriving simultaneous recurrence relations by inserting in any tree with N nodes a new node as a leaf in all the possible ways. The recurrence systems are solved by a simple technique by which we can find both the average value and the variance relative to each property.

The problem of generating random, uniformly distributed, binary trees is considered. A closed formula that counts the number of trees having a left subtee with k -1 nodes ( k =1,2,..., n ) is found. By inverting the formula, random trees with n nodes are generated according to the appropriate probability distribution, determining the number of nodes in the left and right subtrees that can be generated recursively. The procedure is shown to run in time O(n) , occupying an extra space in the order of O(√n)

When planning a database, the problem of index selection is of particular interest. The authors examine a transaction model that includes queries, updates, insertions, and deletions, and they define a function that calculates the transaction's total cost when an index set is used. Their aim is to minimize the function cost in order to identify the optimal set. The algorithms proposed in other studies require an exponential time in the number of attributes in order to solve the problem. The authors propose a heuristic algorithm based on some properties of the cost function that produces an almost optimal set in polynomial time. In many cases, the cost function properties make it possible to prove that the solution obtained is the optimal one.>