A Critical Review on Classification and Terminology of Scissor Structures

When the existing literature on the research of scissor structures is thoroughly investigated, it is seen that different
researchers use different terminologies and classifications especially for the definition of the primary units and
the motion type. Some of the studies define the whole geometry based on the geometric properties of the primary
scissor units and the unit lines while some other studies define it according to the loops. All these studies use
different names for similar elements. This article aims to review the literature on the classification and terminology
of scissor structures and represent the state of art on the studies. Tables are represented showing all approaches
in the literature. In addition, the article criticizes the missing points of each terminology and definition, and
proposes some new terminology. In order to arrive at this aim, different definitions of the primary scissor units
and motion types used in key studies in the literature are investigated thoroughly. With several examples, it is
demonstrated that naming the scissor units according to the resulting motion type might be misleading and it is
better to specify the motion type for the whole structure. A classification for transformation of planar curves is
presented.