What is workspace graph?

I am getting error: “All assigned components must be in the workspace graph”. What is workspace graph and why I am getting this error?

Workspace graph connects all the components along the beam path till it hits the target sample. For example, if a light beam goes through a beam splitter and a delayer before it reaches the target sample, all such components (beam, beam splitter, delayer and sample) will be connected in the workspace graph. These relationships are important for SimphoSOFT Math Kernel to recognize which setup component affect other components during simulation. The beam path is denoted by a dotted line: it starts from the beam component and ends at the sample component. To start simulation the following rules should be satisfied: ●        The beam path starts at a laser and ends at a sample or multi-layer sample ●        All assigned components should be on the path of one of the laser beams ●        Any assigned z-translations must have an associated assigned sample component