* {{Code|txtl}}: Heap file with ID lists.
* {{Code|txtr}}: Index file with references to ID lists.
The '''Attribute Index''' is contained in the files {{Code|atvl}} and {{Code|atvr}}; it uses , the '''Token Index''' in {{Code|tokl}} and {{Code|tokr}}. All have the same layout.
For a more detailed discussion and examples of these file formats please see [[Index File Structure]].