Abstract: Systems and methods are provided for evaluation of networks and changes thereto using automated analysis of network models. The automated analysis can be used to determine how to implement and mutate networks efficiently and effectively, to determine whether and why network resources are unable to communicate with each other, and the like. Automated analysis can allow users (e.g., network administrators) to define networks and pose changes to networks using high-level policies (e.g., written in a declarative language), have those polices automatically translated to lower-level implementation operations for analysis, and in some cases have results of the analysis presented back to the users in an easy-to-understand form.

Abstract: A litterbin, in particular a litterbin which has no inner barrel design, has an additional positioning mechanism for maintaining a litterbag, and is advantageous in that the litterbag will not be exposed to the outside thereof and will not slip, and the manufacturing cost thereof can be reduced. The litterbin includes a barrel body having an opening edge with a positioning mechanism mounted on said opening edge. The positioning mechanism includes a frame mounted on said opening edge and having plural positioning elements thereon, and a ring component positioned on said frame through each of said positioning elements. In this case, the ring component is surrounded by a litterbag so that the litterbag can be tightly clipped between said ring component and each of plural positioning elements on said frame.