Integrating content-based access mechanisms with hierarchical file systems

We describe a new file system that provides, at the same time, both name and content based access to files. To make this possible, we introduce the concept of a semantic directory. Every semantic directory has a query associated with it. When a user creates a semantic directory, the file system automatically creates a set of pointers to the files in the file system that satisfy the query associated with the directory. This set of pointers is called the query-result of the directory. To access the files that satisfy the query, users just need to de-reference the appropriate pointers. Users can also create files and sub-directories within semantic directories in the usual way. Hence, users can organize files in a hierarchy and access them by specifying path names, and at the same time, retrieve files by asking queries that describe their content. Our file system also provides facilities for query-refinement and customization. When a user creates a new semantic sub-directory within a semantic directory, the file system ensures that the query-result of the sub-directory is a subset of the query-result of its parent. Hence, users can create a hierarchy of semantic directories to refine their queries. Users can also edit the set of pointers in a semantic directory, and thereby modify its query-result without modifying its query or the files in the file system. In this way, users can customize the results of queries according to their personal tastes, and use customized results to refine queries in the future. That is, users do not have to depend solely on the query language to achieve these objectives. Our file system has many other features, including semantic mount-points that allow users to access information in other file systems by content. The file system does not depend on the query language used for content-based access. Hence, it is possible to integrate any content-based access mechanism into our file system.