In this study, we describe the methodology used to identify and validate a set of expert-defined fraction subtraction related attributes. These attributes are expected to be mastered by 6th grade students toward proficiency in fraction subtraction. This research argues and demonstrates that state standards guiding subject instruction plays an important role in the identification of the domain related fundamental attributes. This study also illustrates complete implementation of cognitive diagnosis model framework, which is used to extract diagnostic information about students' specific strengths and weaknesses.