WinFS is the code name of a Windows storage subsystem, being developed by Microsoft for use on its Windows operating system. WinFS is a relational database that represents itself to the operating system as a file storage subsystem. The codename WinFS stands for Windows Future Storage but will change before the technology is released; Windows Storage Foundation is the most likely candidate. In 1992, its precursor was called the Object File System (OFS) and was planned to be a part of Cairo, the Microsoft Codename for an undefined future version of Windows. It was not, however, included in any Windows release.
WinFS aims to bridge the worlds of traditional relational databases, objects, XML, and file systems of unstructured documents with the concept of metadata over files. Rather than representing a file solely by directory path and filename, WinFS represents individual domain objects - e.g. e-mails, address book entries, and any kind of regular file - with indexed and searchable context and keyword information.
The underlying system is loosely based on Microsoft SQL Server's engine. WinFS provides access to data through both traditional file-based APIs, and new object-based approaches that take advantage of the new features. Applications that are not written to take advantage of WinFS can access the contents of a WinFS Store through a UNC path.