Immediate feedback has a positive effect on the performance of a student practising a procedural skill in exercises. Giving feedback to a number of students is labour-intensive for a teacher. To alleviate this, many electronic exercise assistants have been developed. However, many of the exercise assistants have some limitations in the feedback they offer.
We have a feedback engine that gives semantically rich feedback for several domains (like logic, linear algebra, arithmetic), and that can be relatively easy extended with new domains. Our feedback engine needs to have knowledge about the domain, how to reason with that knowledge (i.e. a set of rules), and a specified strategy. We offer the following types of feedback: correct/incorrect statements, distance to the solution, rule-based feedback, buggy rules, and strategy feedback.
We offer the feedback functionality in the form of light-weight web services. These services are offered using different protocols, for example by JSON-RPC. The framework around the services is set up in such a way that it can easily be extended with other protocols, such as SOAP. The services we provide are used in exercise assistants such as MathDox, ActiveMath, and our own exercise assistant.
Our feedback services offer a wide variety of feedback functionality, and therefore exercise assistants using our services can construct different kinds of feedback. For instance, one possibility is to start giving correct/incorrect feedback, and only start to give semantically rich feedback on individual steps when a student structurally fails to give a correct answer. Another possibility is to force the student to take one step at a time, or to follow one specific strategy.
In this paper, we describe the feedback services we offer. We briefly discuss the feedback engine that serves as a back-end to our feedback services. We will give examples of how to use our services. In particular, we will show a web- based application that uses the feedback services in the domain of simple arithmetic expressions.