Directed Graphs

Directed Graphs may be used to represent a wide variety of situations:

• simple flows between components
• simple state transitions
• cause-effect relationships
• sub-goal to goal relationships

This application accepts a simple comma-separated file and generates either a directed graph (using GraphViz) or a matrix. One purpose of this tool is to demonstate the idea that a single model (as described by the text file) may be presented in differnt forms with different or views

• Run the application
• Sample Models
  • A simple flow model from Weinberg and Weinberg General Principles of Systems Design Dorset House (1979) p77
  • A Cause-effect model of a Flameout error on the ? spacecraft
  • A Goal hierarchy from Stewart Green's PhD thesis
  • A causal model for the Thames Barrier
  • A process model of the Punch-out e-business process.
  • An example process model from Martin Ould's RAD work
  • The activity sequence diagram for post launch activities
• File format is multiple lines, each defining a node and its outgoing links as a sequence of comma separated variables:
  • Node ID : a number or short name
  • Node name : a longer descriptive name (with no embedded commas)
  • zero, one or more comma separated node ids of dependent nodes. A node id may be qualified by a + or - indicating a positive or negative influence in a causal model

Work to do

• Function to re-order the rows (and the columns) to cluster the interactions in the matrix - cf Alexander
• Function to generate a reachability matrix, showing the next + or - influence
• XML input
• Support special forms of directed graphs e.g.
  • State Transition diagrams
  • process models with OR and AND nodes
  • typed interactions - e.g initial input, continuous input, control, mechanism - as coloured arcs
  • typed nodes e.g. Actors of processes
  • Swimlanes
  • Interactive graphical creation of the graph

Production

• graph.php
• tree2gifobj.php

Chris Wallace 2005