A system is disclosed for monitoring condition of a railways installation such as a points machine. An object is recursively selected from a group of objects that consists of the tag and the expression, and is used in advancing through the corpus until a candidate document is found that contains the tag and satisfies the expression. Instead the designer can receive and send the project as a single file and work with it as if it were a single document. Combustion velocities averaging 3,050 ms are observed for PS films with specific areas of \u02dc840 m2g and porosities of about 65-67%.