Abstract: As autonomous-ness is inevitable in network information services to achieve more intelligent human-machine interaction, a situation calculus-based modeling methodology is proposed for this purpose. Based on Reiter's situation calculus, a validity theory is introduced to enrich common-knowledge-based validity computing, a hierarchical knowledgebase is introduced to make situation calculus easier for technicians and developers to understand, and an XML-based ad-hoc script language, ScML, is developed to make situation calculus processable by computers as constructed texts. ScML's syntactical verification can be easily achieved with XML schema, and program generation with XML XSL. This methodology is demonstrated by an autonomous calendaring service.