This paper describes an approach to derive assessments about information 
      sources based on individual feedback about the sources. We describe 
      TRELLIS, a system that helps users annotate their analysis of 
      alternative information sources that can be contradictory and 
      incomplete. As the user makes a decision on which sources to dismiss and 
      which to believe in making a final decision, TRELLIS captures the 
      derivation of the decision in a semantic markup. TRELLIS then uses these 
      annotations to derive an assessment of the source based on the 
      annotations of many individuals. Our work builds on the Semantic Web and 
      presents a tool that helps users create annotations that are in a mix of 
      formal and human language, and exploits the formal representations to 
      derive measures of trust in the content of Web resources and their 
      original source.