Sentence:  The system well understands that one of its primary responsibilities <WSD>is</WSD> to bring children and books together ; consequently an experienced children 's librarian at headquarters conducts a guidance program designed to promote well-planned library activities , cooperating with the children 's librarians in member libraries by means of individual conferences , workshops , and frequent visits . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)