There is a growing interest in using Web services as a reliable medium for data sharing among different data providers and users. Recently, enterprises are using service oriented architecture for data sharing in Web by putting data sources behind web services instead of creating database applications. These types of web services are called as Data-providing (DP) Web services. In DP web services there is a challenge to provide a broad spectrum of enterprises the capability to exploit the data and information that is normally stored in distributed and heterogeneous information systems. This paper introduces a model of web service system that integrates distributed data sources and facilitates sharing of data through web services. The web services are built on top of existing data sources and the system enables the exchange of data through services. We also discuss service selection and query rewriting techniques for processing queries over data providing web systems.