Influence diagram

Strategy tables and influence diagrams can also be important management methodologies for coherent as well as shared planning (53). Strategy tables hst alternative product concepts, design options, as well as technical and market alternatives. 

Influence diagrams can be used with the strategy tables to identify factors or variables that create uncertainty in assessing the value of various options. Issues can be quaUtatively prioritized in selecting the best path to generate value for the business. 

History and Technical Basis. The influence diagram approach (IDA) (also known as the sociotechnical approach to human reliability (STAHR) (see Phillips et al., 1990) is a technique that is used to evaluate human error probabilities as a... 

Phillips, L. D., Embrey, D. E., Humphreys, P., Selby, D. L. (1990). A Sociotechnical Approach to Assessing Human Reliability. In R. M. Oliver J. A. Smith (Eds.), Influence Diagrams, Belief Nets and Decision Making Their Influence on Safety and Reliability. New York Wiley. 

In a tiny fraction of cases, a quick formula can be used. For most cases, the analysis uses an options tree, with one leaf per possible outcome. However, this falls prey to the curse of dimensionality —the number of leaves on the tree grows exponentially in the number of risk and decision dimensions considered. Thus only a limited, simple set of situations can be optimized in this way because one has to severely limit the decisions and risks that are considered. Tools available to help automate and simplify options analysis, widely used in pharmaceutical project evaluation, include Excel addons such as R1SK [11] and more graphically based solutions such as DPL [12]. Both of these support the creation and evaluation of decision trees and of influence diagrams Figure 11.2 shows a simple example of each of these. A primer in applied decision theory is Clemen s book Making Hard Decisions, other sources may be found in the website of James Vornov, Director of Clinical Research at Guildford Pharmaceuticals, a recent convert to decision theory for options analysis [13]. 

R.A. Howard, J.E. Matheson, Influence Diagrams in the Principles and Applications of Decision Analysis, Editors R.A. Howard, J.E. Matheson, Strategic Decisions Group, Menlo Park, CA, Vol. II, pp. 720-762. 

R.D. Schacter, Probabilistic Influence and Influence Diagrams, Operations Research, Vol. 36, 1988, pp. 589-604. 

Let us now see how the ideas of the previous section can be used to construct the variable-influence diagram, that defines the paths leading to top-level event. Consider a set of four modeling relationships, represented by the structural matrix shown below. 

Fig. 21. The variable-influence diagram resulting from Assumption-1 and Assumption-2. 

TLE is to change the heat of reaction and obviously implies a change in chemistry. Furthermore, the variable-influence diagram makes explicit that top-level event prevention necessitates the placement of control objectives on every variable that immediately precedes the top-level, i.e., variables Tq, Tp, (2ri Pi Pi should come under control. 

Figure 3 Influence diagrams for two reaction networks involving three reactants, X, Y, and Z. Arrows indicate the direction of influence plus signs correspond to activation, minus signs correspond to inhibition. In diagram A, X activates Y, Y activates Z, and Z activates X. In diagram B, X activates Y, Y activates Z, but Z inhibits X. (After King 1980.)...

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