Current Web users usually have their own files, work documents, communications and personal contacts distributed in the storage systems of many widely-used Internet services (e.g. Google Docs, Gmail, Facebook and Zoho). Therefore, they face the challenge of being not able to have an integrated view for their related data objects (e.g. mails, pics, docs and contacts). Recently, most of the major Internet services provide standard APIs that allow developing software applications that can read and write data from their underlying data store after providing the credential access information of registered accounts.