Chapter 1 Introduction
1.1 Purpose and Significance
System reliability theory is one of the basic theories of safety science. Derived from system engineering， system reliability is mainly concerned with the possibility of system faults and accidents. Owing to improvements in modern science and indus-trialisation， to pursue greater economic and strategic goals， some countries have intensified their research and established large or super-large systems to meet their requirements. However， it was found that a decline in reliability occurs during the operation of a system with an increase in system complexity. In this case， the original problem is that the lessons learned after an accident cannot meet the requirements of the present system safety. Because the research method of the problem is primarily applicable to a low value of system， with low system reliability and no critical con-sequences of a fault， such a research approach is not significant for today's large-scale and extremely complex systems. Therefore， during the 1950s， Britain and the US first proposed the concept of safety system engineering. At this time， some concepts of system engineering were introduced into the field of safety， particularly a reliability analysis method， and applied in the miltary and aerospace fields. Safety system engineering is， therefore， one of the basic aspects of safety science.
Safety system engineering and system reliability analyses have since been developed under the conditions of relatively simple and low complexity systems and limited data scales. However， with the development of big data technology， in telli-gent science， system science， and related mathematical theories， existing system reliability analysis methods have also exposed certain problems， such as big data processing; reliability causation， stability， and reverse engineering; and the deion of reliability changes. At the same time， existing system reliability analysis methods are mostly targeted at specific systems. Although such an analysis is effective， there has been a lack of abstraction at the system level， making it difficult to meet the required universality， scalability and adaptability. Therefore， the system reliability analysis method that achieves the above capabilities and meets future technological requirements is needed. It is， therefore， necessary to combine the system reliability analysis with intelligent science and big data technology.
Space fault tree theory (SFT) [1] is a systerm reliability analysis method proposed by the authors in 2012. After some years of development， the preliminarily foun-dation of the SFT theory framework has been completed， which can satisfy the reliability analysis of a simple system， including big data processing， reliability causality， reliability stability， reliability reverse engineering， and a reliability change deion，and achieves high universality， extensibility， and adaptability. Its development process integrates intelligent science and big data processing technology， including factor space theory [2]， fuzzy structured element theory [3]， and cloud model theory [4]， among others. Although some problems remain， the
SFT still has adequate room to solve these issues through further development.
We hope this book will broaden the basic research field of safety science， enabling readers to better understand SFT theory， factor space theory， and their role in the system reliability analysis， soeking a thoretical development of reliability adapted to intelligent science and big data technology.
1.2 Summary of Research and Problems
1.2.1 Fault Tree Research
The fault tree is an important aspect of safety system engineering and plays a crucial role in the analysis of system safety and reliability in several industries. It has been widely used and studied around the world as a systermatic scientific method. The applications of the fault tree and studies conducted in different fields are reviewed in the following chapter.
In medical research， the fault tree has been applied to the control of hand， foot， and mouth diseases [5]. For the safety of a laboratory-scale bioreactor， the fault tree analysis method was used to deal with hydrogen sulphide biotreatment [6]. In research into uncertainty， the problem was studied using fault tree [7. In addition， the decision tree method has been used to represent uncertainty based on proba-bility [8]. An uncertainty analysis of fault tree model based on basic events was also developed [9]. In addition， uncertainty in fault tree analysis was processed using a hybrid probabilistic-possibilistic framework [10]. In a study on system reliability analysis， a real-time systern analysis method based on fault tree was proposed [11]. A study on a non-repairable system was also conducted using dynamic fault tree and priority AND gates [12]. In an analysis of system safety， an extended fault tree was used to analyse the