Data Warehousing and OLAP technologies enable enterprises to achieve Business Intelligence (BI). Since the Web is the largest independent information repository, systematically integrating suitable Web data into a data warehouse will benefit the enterprise. This paper introduces a Web data warehousing system in the MOLAP environment. A transformation approach is proposed to construct a base cube and then aggregates are precomputed over the base cube. To specify the aggregation rules we have developed a SQL style language that uses external functions for retrieving array data, computing aggregates, populating aggregated cubes.