Since the establishment of Paris Memorandum of Understanding in March,1982,the PSC developed from the Europe Mou region into nine regions with the past twenty-five years.

The most frequently employed forms of the document at theconstruction sites of large imported and exported plants are theEnglish daily log and memorandum which deal with variousissues or problems concerning technology,econmy and manage-ment of the construction.

Founded on Least Cost search-LC search,an improvement shortest path algorithm was produced which takes the crossway corners as crunodes and introduced the memorandum which storages the shortest-path information,as to enhance the efficiency and flexibility of the query.