The majority of publications included in this review use assignments with binary specifications and 2-level assignment outcomes. In this approach, a student's work either does or does not meet an individual specification. The instructor sets a threshold, i.e. a number of specifications that must be met for the overall assignment to earn credit. Instructors may also set some specifications as "required" so that the assignment does not earn credit if those "required" specifications are not met, regardless of how many others are met. Wording for the assignment outcomes varies, but some of the common phrases that have been used are pass/fail, satisfactory/unsatisfactory, satisfactory/needs revision, meets specifications/does not meet specifications, accept/revise, or complete/incomplete .