Sorting techniques are a well-known method for capturing the way experts compare and order concepts, and can lead to the revelation of knowledge about classes, properties and priorities.
The simplest form is card sorting. Here the expert is given a number of cards each displaying the name of a concept. The expert has the task of repeatedly sorting the cards into piles such that the cards in each pile have something in common. For example, an expert in astronomy might sort cards showing the names of planets into those that are very large, those that of medium size and those that are relatively small. By naming each pile, the expert gives information on the attributes and values they use to denote the properties of concepts. Variants of this involve sorting objects or photographs rather than cards in domains where simple textual descriptors are not easy to use.
A technique often used in conjunction with sorting techniques is triadic elicitation (aka 'Three Card Trick'). This technique prompts the expert to generate new attributes. This involves asking the expert what is similar and different about three randomly chosen concepts, i.e. in what way are two of them similar and different from the other. This is a way of eliciting attributes that are not immediately and easily articulated by the expert.
Other Knowledge Acquisition Techniques:
Protocol Analysis techniques
Repertory Grid technique
Limited-Information and Constrained-Processing tasks