Visualization is essentially a cognitive process in which humans form a mental model or image in their minds to enable them to comprehend complex information about the artifacts, relationships, process, phenomena, etc. under study. Computer based visualization environments combine interactivity with visual renderings of the data in the form of suitable tools and techniques to support this comprehension process. In spite of the plethora of visualization tools and techniques that have evolved, visualization environments are often not very effective in their support of this comprehension process. Clearly we need quantitative measures to asses the effectiveness of a visualization environment. Given the cognitive nature of visualization the two main questions are---what do we asses and how? In this research, we have adopted a systematic approach towards providing answers to these questions. We identify that there could exist a gap between the information "communication" intent of the visualization environment and the information "seeking" intent of the user. Our premise is that smaller this gap more effective is the visualization environment in terms of information comprehended by the user.