Physical Architecture Diagram (PAD)

These diagrams show the physical structure of some or all of a system at a particular level. The PAD shows the physical flows between the system components at the level of interest.

Every symbol in the diagram represents something physical, including paths through which data passes. Therefore, a data link on a PAD corresponds to a physical interface connection, i.e., cable, bus, and so on.

It will be common to have both an AID and a collection of PADs in an architecture model. The AID will show the physical components and the logical connections between them. There will be one or more associated PADs, each showing the same physical components, but showing alternative physical connections (such as a bus or point-to-point links) by which these components are interconnected in that specific topology). PADs are hierarchical. Their connectivity is:

PADs can only appear in models in the Implementation Domain.

Numbering of PADs

The numbering system for PADs is alphanumeric dot-decimal.

The start of each architecture is a top-level PAD that is typically given a number to represent that architecture. The hierarchy of diagrams and specifications created below it will follow this number with a dot-decimal suffix.

Symbols

An example PAD is:

The symbols available in PADs are:

Symbol	Name	Description	Definition	Expansion
	Comment	Makes a note anywhere in the diagram. Are always surrounded by * characters.	None	None
	Boundary Point	A connection point for the initial transition to enter the initial state.	None	None
	Environment	Represents external system or environment to this system.	Environment	None
	Bus	Represents a network bus for passing data from one piece of physical equipment to another.	Equipment specification	PAD
	Equipment	Represents a piece of hardware equipment within the system construct.	Equipment specification	PAD DFD BD UCD
	Library Equipment	Represents a piece of shared hardware equipment within the system construct.	Equipment specification	PAD
	Link	Represents an interface link between two physical pieces within the construct.	Data definition	None
	Picture	Allows you to choose the location of a GIF or JPEG image to be displayed as a diagram symbol or to be embedded in an existing diagram symbol.	None	None