Consider the following retrieval formula: Where c(w, D) is the count of word w in document D, dl is the document length, avdl is the average document length of the collection, N is the total number of documents in the collection,

Consider the following retrieval formula:

Where c(w, D) is the count of word w in document D,

dl is the document length,

avdl is the average document length of the collection,

N is the total number of documents in the collection,

and df (w) is the number of documents containing word w.

In view of TF, IDF weighting, and document length normalization, which part is missing or does not work appropriately?