Introduction to Functional Dependency Network Analysis

Critical considerations in engineering enterprise systems are identifying, representing, and measuring dependencies between suppliers of technologies and providers of services to consumers and users. The importance of this problem is many-fold. Primary is enabling the study of ripple effects of failure in one capability on other dependent capabilities across the enterprise. Providing mechanisms to anticipate these effects early in design enables engineers to minimize dependency risks that, if realized, can have cascading negative effects on the ability of an enterprise to deliver services to users. The approach to this problem is built upon concepts from graph theory. Graph theory enables (1) a visual representation of complex interrelationships between entities and (2) the design of analytical formalisms that trace the effects of dependencies between entities as they affect many parts and paths in a graph. In this context, an engineering system is represented as a directed graph whose entities are nodes that depict direction, strength, and criticality of supplier-provider relationships. Algorithms are designed to measure capability operability (or inoperability) due to degraded performance (or failure) in supplier and program nodes within capability portfolios that characterize the system. Capturing and analyzing dependencies is not new in systems engineering. New is tackling this problem (1) in an enterprise systems engineering context where multidirectional dependencies can exist at many levels in a system’s capability portfolio and (2) by creating a flexible analysis and measurement approach applicable to any system’s capability portfolio, whose supplier-provider relationships can be represented by graph theoretic formalisms. The methodology is named Functional Dependency Network Analysis (FDNA). Its formulation is motivated, in part, by concepts from Leontief systems, the Inoperability Input-Output Model (IIM), Failure Modes and Effects Analysis (FMEA), and Design Structured Matrices (DSM). FDNA is a new analytic approach. One that enables management to study and anticipate the ripple effects of losses in supplier-program contributions on a system’s dependent capabilities before risks that threaten these suppliers are realized. An FDNA analysis identifies whether the level of operability loss, if such risks occur, is tolerable. This enables management to better target risk resolution resources to those supplier programs that face high risk and are most critical to a system’s operational capabilities.