The struggle to assess collaborative work

Recently, I am tasked to table a paper for a new module for my institution. In the paper, I have to explain how I want to assess 1) my learners' attainment of knowledge and skills (AKS), 2) Self-directed learning (SDL) and 3) Collaborative learning (COL). #1 is an evaluation of the product, while #2 and #3 are evaluations of the learning process.  Both are important especially in an educational setting because of the need to inculcate the right mindset and attitude towards learning.

As the main instructional strategy is Problem-Based Learning (PBL), students are required to collaborate in their team and provide a resolution to the problem statement that is handed out at the beginning of the class, culminating in a group artefact. The question is, how do you assess an individual's attainment of knowledge and skills using a group artefact? The struggle exists because we want students to collaborate, and yet it is challenging to give an individual grade using a group artefact. If we add on another individual submission, we run the risk of over-assessing students, and instructors have to grade more, in addition to the group artefact and looking for sources of evidence for SDL and COL for a class of 40 students.

Yes, we want product, we want process, we want students to collaborate. All these are good. But creating a suitable assessment that encompasses all of these without over-taxing the instructors and over-stressing the students require a delicate balance.