In e-commerce the multidimensional data analysis for OLAP (on-line analytical processing) based on the web data needs integrating various data sources such as XML (extensible markup language) data and relational data on the conceptual level. A conceptual data description approach of multidimensional data model was presented in order to conduct multidimensional data analysis of OLAP for multiple subjects. The UML (unified modeling language) galaxy diagram, describing the multidimensional structure of the conceptual integrating data at the conceptuai level, was constructed. The approach was illuminated using a case of 2_roots UML galaxy diagram that takes one retailer and several suppliers of PC products into consideration.