Services such as automatic purchasing, automatic updating of prices, or getting latest information etc, can be provided on the Internet using Web services technology. A client can access these services using the Internet. Web Services infrastructure includes some standards, such as Simple Object Access Protocol (SOAP), Web Services Description Language (WSDL) and Universal Description, Discovery and Integration (UDDI). In this paper we represent distributed web services by modeling the flow of messages and methods in a web service transaction. Such a model assists the web services designer to ensure the correctness of web flows in terms of deadlock and correct termination of the web services transaction. WSDL and methods are modeled using Petri Nets. A software tool is implemented for extracting the model from the WSDL description of the web services flow.