Why are phrases highlighted in search results that are not in the search expression?

Environment:

Oracle B2C Service Knowledge Advanced
Phrase Searching, Results Highlighting

Issue:

The search expression has no exact matches to phrases in any documents, and there is highlighting of different phrases for the search results list.

Resolution:

Knowledge Advanced uses natural language processing to drive the search results. If different words are synonyms of the same concept, this means that for search, they are identical. The search results and highlighting will show the articles that contain synonyms of the concept, even if the synonym diverges from the term in the user question.  

This is the expected behavior because, when the collections are indexed, all the different synonyms of the same concept found in those collections will get annotated with that concept. If the matching with an answer is due to the relationship between the user question words and the synonyms present in our linguistic databases, search is able to make this connection between synonyms.

Additional Resources:

For further information on tuning search and synonyms, see the following:
Knowledge Advanced Tuning Intelligent Search
Understanding Search Concepts for Knowledge Advanced