TheLearning from Observation (LFO) paradigm has been widely applied in various types of robot systems. It helps reduce the work of the programmer. However, so far, the available systems have application limited to rigid objects. Deformable objects are not considered, because: (1) it is difficult to describe their states and (2) too many operations are possible on them. In this paper, we choose knot-tying tasks as case study for operating on deformable objects, since theknot theoryis available and since types of operations are limited. In actuality, we introduce an appropriate representation for describing knot's states and define four types of operations enough to realize any knot-tying tasks.
