Consider a protection system where three access rights x, y, and z are defined on the objects. Show that the set of classes and the flow relation from a lattice. Draw a schematic diagram for the lattice. Schematic diagram of the lattice is shown in figure 14.1. Discuss the pros and cons of the tagged and partitioned approaches to implement a capability based protection system.
Advantage is that capabilities can be intermixed with the regular instructions and data.
Also, the check if a memory word contains a capability is simple. Capabilities can be loaded in the same registers that ared used for regular data. It does not require separate instructions to manipulate capabilities. By separating ordinary data and capabilities, it provides higher protection. For every object, there are two segments , one segment storing only the ordinary data and the other storing only the capabilities of the object.