Web based peer assessment for portfolios has been used as an innovative assessment methods to reuse students portfolio for refining learning. However, without sophisticated support to articulate the assessment contexture about portfolios, students cannot communicate with explicit learning concepts and think reflectively for refinement of their learning. This study attempts to utilize knowledge acquisition and data mining techniques to solve the problems in support contexture awareness. By way of knowledge acquisition and data mining techniques, web peer assessment systems obtain students' personal theories during assessing portfolios. Thereby, teachers and students can go online to fully exchange personal theories, thus allowing them to think reflectively for refinement of learning.