This class diagram shows interfaces and classes for a web recommender system. The interfaces include WebRecommender, SearchEngine, QueryFormulator, and QueryTermGenerator. The classes include StructureFeatureRecommender, SemanticFeatureRecommender, StatisticFeatureRecommender, YahooEngine, GoogleEngine, YahooQueryFormulator, GoogleQueryFormulator, and TFIDFQueryTermGenerator. The classes implement methods like Recommend(), Search(), CreateQuery(), and generateQueryTerms().

1. Class Diagram setQueryFormulator(QueryFormulator qf) <<interface>> WebRecommender Recommend(Page p): List<Page> <<interface>> SearchEngine Search() : List<Page> StructureFeatureRecommender Recommend(Page p): List<Page> SemanticFeatureRecommender Recommend(Page p): List<Page> YahooEngine Search(QueryFormulator qf) : List<Page> GoogleEngine Search(QueryFormulator qf) : List<Page> <<interface>> QueryFormulator CreateQuery(List<String> ls): List<String> YahooQueryFormulator CreateQuery(List<String> ls): List<String> GoogleQueryFormulator CreateQuery(List<String> ls): List<String> <<interface>> QueryTermGenerator generateQueryTerms(List<String> keyTerms) : List<String> TFIDFQueryTermGenerator generateQueryTerms(List<String> keyTerms) : List<String> StatisticFeatureRecommender Recommend(Page p): List<Page>