What made you want to look up negative valence? Please tell us where you read or heard it (including the quote, if possible).
WBS is nothing but Work Breakdown Structure. It is mainly used in Project System (PS) module. Tcode: CJ20N. For any project defined we must have atleast one WBS. Within this WBS we can have networks. Networks are nothing but the series of activities. Material are used to perform the activities.
A WBS Dictionary is merely a supporting document, which provides the definitions for each component contained in the Work Breakdown Structure. This type of dictionary is often recommended as a reference resource material for task-oriented projects comprising several work phases.