International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 02 Issue: 09 | Dec-2015 www.irjet.net p-ISSN: 2395-0072 © 2015, IRJET ISO 9001:2008 Certified Journal Page 299 COMPONENT SAFETY ASSESSMENT USING THREE-STATE MARKOV CHAIN MODEL Gandi Satyanarayana 1 , Dr. P. Seetharamaiah 2 1 Research Scholar, Computer Science & Engineering, GITAM University, AndhraPradesh, India 1 Professor Emeritus, Computer Science& System Engineering, Andhra University, AndhraPradesh, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - In this Paper, we use a stepwise solution in order to model both design faults and physical faults through a three-state homogenous Markov model that is used to solve three state non homogeneous Markov chain for the component modeling. Four parameters are used in the modeling of the three-state Markov chain model. By using the parameterized three-state Markov model Component safety assessment is conducted by the assumption that component does not utilize redundancy. Key Words: Safety-critical computer systems, Faults, hazard, Errors, Failures, Physical Fault, Design Failures, Safe Failures, Unsafe Failures, Coverage, Failure rate, 1. Introduction Safety-critical system and computer system are the two concepts concerned in a safety critical computer system. A safety-critical system is a system whose faulty function could have very serious effects such as the loss of severe injuries, large-scale environmental spoil, human life, or large cost-effective penalties, A computer system [IEEE 729] is a system composed of computer, peripherals, and the software essential to make them work together. Here we deal with component modeling and assessment. A system is comprised of at least one component. The assumption in modeling of components is that component does not utilize redundancy. A simplex system is a system that does not utilize redundancy frequently. [Dunn2002]. Redundancy is the usage of additional resources further than those needed for the normal system operation for the purpose of achieving fault tolerance [Johnsonl989]. Fault tolerance is the ability of a system to continue to perform its tasks properly during and after the occurrence of hardware and/or software faults [Johnson 1989]. For example, in Triple Modular Redundancy (TMR), a typical fault tolerant design is achieved through three redundant components. A system can be designed with both fault tolerant mechanisms and fault detection mechanisms. A component cannot have any fault tolerant mechanisms, but a component can have fault detection mechanisms. Actually Components are the building blocks of a system. By the assumption that a component is non-redundant, the fault universe and the failure universe of a component is a one-to-one mapping, as shown in Figure 1-1. Figure 1-1 Component Fault-Failure Mapping 1-1 Hazard, Faults, Errors and Failures A system may not always achieve the desired aim .The factors of reliability of a system arises due to causes and effects of deviation from the system functioning. The following definitions come from [N.G.Leveson 2001]. Definition 1.1: Hazard is the potential to cause harm to people, Environment, Asset and Reputation of an organization. Definition 1.2: Fault is a physical defect, imperfection, or flaw that occurs within some hardware or software component. Definition 1.3: Error is a design flaw or deviation from a desired or intended state. Definition 1.4: Failure is the non-performance or inability of a system or component to perform its intended function for a specified time under specified environmental conditions. Mapping for a Component Fault Universe Failure Universe