Hardware Network Trees
Hardware Network Trees are topologically constructed from the hardware schematics and other electrical connectivity data. Using IDA’s approach, current flow is from top to bottom, signal flow is from left to right, and adjacent nodes are collapsed into a single node thus connections between circuit cards are collapsed into their functional connectivity. The number of line crossings are minimized allowing an easier understanding of the Network Tree’s function. Circuit symbols are simplified to show all the inputs that affect a single output. Network Trees are interconnected by cross references which may include Software Network Trees and all system hardware is included on a Network Tree.

Software Network Trees
Software Network Trees are based on the same topological aspects as Hardware Network Trees. Each Software Network Tree represents a software function or subfunction and all software instructions are part of a Network Tree. Program branches and data flow are graphically depicted with cross references between Network Trees maintain program flow for branches. All program variables are cross referenced between Network Trees indicating where the variable is defined (or redefined) and where it is referenced. Hardware interfaces to Hardware Network Trees are also shown via the cross-references.

Network Forests
Network Forests are used to interconnect Hardware and Software Network Trees. A Network Forest is developed for each physical system output. A graphical representation of all Network Trees is shown in a topological manner that depict a single system function with each block on the Network Forest being a Network Tree. Directional arrows show input/output relationships between Network Trees. The system output being analyzed is on the right of the forest, with signal flow left to right thus defining a system output in terms of all controlling inputs. All hardware/software interfaces are clearly shown.

Program Operation Diagram
A Program Operations Diagram or POD, is developed for the system software if present. The POD shows the run-time relationships between Software Network Trees. The Exec. or real-time loop is at the top, and Software Network Trees that are called by the real-time loop are shown below in the order that they are called. All Network Trees are depicted including any utilities and Interrupt Service Routines (ISRs). Hardware and Software interfaces are also shown.