As a Sling parser recognizes an input program, it must build a composite command that represents the program. Assembler subclasses do the work of building this command, sharing certain objects during parsing. The assemblers use a target object to contain the common objects the assemblers need while parsing a Sling program. The target is a single object of class SlingTarget containing a scope, two sliders, and a RenderableCollection object. The assemblers update the target and leave one or more Command objects on the assembly's stack. Figure 16.27 shows the SlingTarget class.