Answer to Question 1
A walkthrough is a peer group review of any product created during the systems development process. During the review users, management, and the development group participate through various roles. These roles are coordinator, presenter, user, secretary, standards bearer, and maintenance oracle. The coordinator is the person who plans the meeting and facilitates a smooth meeting process. The presenter is the individual who describes the work product to the group. Ensuring that the work product meets the needs of the project's customers is the role fulfilled by the user. The person taking notes and recording decisions or recommendations made by the group is the secretary. The standards bearer role is to ensure that the work product adheres to organizational technical standards. The maintenance oracle is the individual who reviews the work product in terms of future maintenance activities.
Answer to Question 2
The act of going from a single system to four component processes is called (functional) decomposition. Functional decomposition is an iterative process of breaking the description or perspective of a system down into finer and finer detail. This process creates a set of hierarchically related charts in which one process on a given chart is explained in greater detail on another chart. Each resulting process (or subsystem) is also a candidate for decomposition. Each process may consist of several subprocesses. Each subprocess may also be broken down into smaller units. Decomposition continues until you have reached the point at which no subprocess can logically be broken down any further. The lowest level of a DFD is called a primitive DFD.