Step 1. Analyze the user query to generate/update the sensor dependency tree based upon the ontological knowledge base and the multi-level view database that contains up-to-date contextual information in the object view, local view and global view.

Step 2. If the sensor dependency tree is empty, perform fusion operation (if multiple sensors have been used) and then terminate. Otherwise build/refine the s-query based upon the user query, the sensor dependency tree and the multi-level view database.

Step 3. Execute the portion of the s-query that is executable according to the sensor dependency tree.

Step 4. Update the multi-level view database and go back to Step 1.