Given the following table of possible values of each attribute, how many bit vectors would we require in total to construct the inverted files?
| Attribute | Values |
|---|---|
| manufacturer | Sekine, Raleigh, Miele, Nishiki, Apollo, Norco |
| colour | white, red, black, blue, green, silver |
| type | touring, mountain, racing, hybrid |
Instead, we are to implement the inverted file using the graph structure as discussed in class, with the following node structure:
| Pointer | Size |
|---|---|
| pointer to main file | 4 bytes |
| pointer to directory for manufacturer attribute | 4 bytes |
| pointer to next node with same manufacturer | 4 bytes |
| pointer to directory for colour attribute | 4 bytes |
| pointer to next node with same colour | 4 bytes |
| pointer to directory for type attribute | 4 bytes |
| pointer to next node with same type | 4 bytes |
Show the format of the directory for this inverted file, and then write an algorithm in pseudocode which will search for all of the white Miele racing bikes.
Assuming that each value of every attribute appears reasonably frequently in the main file, describe two changes which could make the node structure more space-efficient.