Each EQL expression used in the stratify statement corresponds to a stratum, as does the set of records which do not match any expression, producing k + 1 strata (where k is the number of EQL expressions). Records are placed in the stratum associated with the first EQL expression they match. The first stratum is the highest ranked, the next stratum is next-highest ranked, and so forth. Note a record will be stratified in the highest strata it matches, so boosting will have priority over burying.

If a record matches none of the specified EQL expressions, it is assigned to the unmatched stratum. By default, the unmatched stratum is ranked below all strata. However, you can change the rank of the unmatched stratum by specifying an asterisk (*) in the list of EQL expressions. In this case, the asterisk stands for the unmatched stratum.

The rules for using an asterisk to specify the unmatched stratum are:

This Ntx snippet shows the use of an asterisk in the query:

N=0&Ntx=rel+stratify(collection()/record[Score>90],*,collection()/record[Score<50])

The query will produce three strata of records:

Note that the EQL expressions must be URL-encoded. For example, this query:

collection()/record[status = 4]

should be issued in this URL-encoded format:

collection%28%29/record%5Bstatus%20%3D%204%5D

However, the examples in this chapter are not URL-encoded, in order to make them easier to understand.


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