# Block Definition Diagram Constructs

The ‘Block Definition Diagram’ supports eight unique diagram constructs: a ‘Block,’ a ‘Port,’ a ‘Value,’ a ‘Constraint,’ an ‘Operation,’ an ‘Input Parameter,’ a ‘Return Type,’ and a ‘Logical Connection.’ Each diagram construct is described in more detail below:

• ## Block

In the system model, an Asset entity with label ‘Block’ is used to represent a ‘Block’ construct. A ‘Block’ must be added to the diagram first before any of the other constructs can be added. In the diagram, this construct is represented as a rounded box and contains the name of the ‘Block’ in the top section.

• ## Port

In the system model, a Port entity is used to represent a ‘Port’ construct. A ‘Block’ must be added to the diagram first before this construct can be added. In the diagram, this construct is represented as a small square on the edge of a ‘Block’ with the name of the ‘Port’ underneath.

• ## Value

In the system model, a Characteristic entity is used to represent an ‘Value’ construct. A ‘Block’ must be added to the diagram first before this construct can be added. In the diagram, this construct is represented as a line of text containing the name of the ‘Value,’ a semicolon, and the units of the ‘Value’ in middle section of the ‘Block.’

• ## Constraint

In the system model, an Equation entity is used to represent an ‘Constraint’ construct. A ‘Block’ must be added to the diagram first before this construct can be added. In the diagram, this construct is represented as a line of text containing the name of the ‘Constraint’ in bottom section of the ‘Block.’

• ## Operation

In the system model, an Action entity is used to represent an ‘Operation’ construct. A ‘Block’ must be added to the diagram first before this construct can be added. In the diagram, this construct is represented as a line of text containing the name of the ‘Operation’ in bottom section of the ‘Block.’

• ## Input Parameter

In the system model, an Input/Output entity is used to represent a ‘Input Parameter’ construct. An ‘Operation’ must first be added to a ‘Block’ in the diagram before this construct can be added. In the diagram, this construct is represented as a line of text containing the name and units of the ‘Input Parameter’ in parenthesis.

• ## Return Type

In the system model, an Input/Output entity is used to represent a ‘Return Type’ construct. An ‘Operation’ must first be added to a ‘Block’ in the diagram before this construct can be added. In the diagram, this construct is represented as a semicolon and a line of text containing the units of the ‘Return Type.’

• ## Logical Connection

In the system model, a Logical entity is used to represent a ‘Logical Connection’ construct. At least two ‘Block’ constructs must be added to the diagram first before a ‘Logical Connection’ can be added. In the diagram, this construct is represented as a solid line connecting two ‘Block’ constructs and a line label containing the name of the ‘Logical Connection.’