1cdf8355_s_of_a_Faceted_Navigation_OPAC__Logical_Rule
[Coded Action] Text Search [Explanation] First appearance of a search string within a session [Logical Rule] 
Ntt has a value. Value is different from previous Ntt value. Ntt value has not appeared previously in the same session. If multiple values have changed, Ntt change takes precedence.
The Code4Lib Journal – Extracting User Interaction Information from the Transaction Logs of a Faceted Navigation OPAC