DeXIN (Distributed extended XQuery for data INtegration) integrates multiple, heterogeneous, highly distributed and rapidly changing web data sources in different formats, e.g. XML, RDF and relational data. DeXIN is a RESTful data integration web service which integrates heterogeneous distributed data sources, including data services (DaaS – data as a service). At the heart of DeXIN is an XQuery extension that allows users/applications to execute a single query against distributed, heterogeneous web data sources or data services. In this system demo, we show how DeXIN can provide an optimized, distributed and parallel query processing and data integration at the same time.