In this paper, we present the nExaminer framework for semi-automated assignment assessment in an open source virtual learning system, namely, Moodle. The motivation for developing the framework is established on the observation of a major problem associated with traditional assignment assessment in Moodle - managing an effective relationship between the instructor and the students is difficult. Thus, the design and implementation of the nExaminer framework is discussed, along with the advantages it provides to both students and instructors. Experimental results with the nExaminer framework have been encouraging. It shows that the framework provides instructors with the ability to semi-automatically generate subjective feedback and automate the process of objective assessment within Moodle in an efficient manner. Moreover, the results also manifest that students are motivated by the usage of automated objective assessment in the nExaminer framework.