## 3 Hazard Analysis Foundations and Key Terms of STPA and ISO26262
### Key Terms of ISO26262 Concept Phase and STPA  
Key terms of STPA and ISO26262 HARA process are listed in Table 2. We could see the conceptual differences between the two from the table. Taking the definitions of hazard as an example, firstly, the scope of a hazard in STPA is much broader than the scope of a hazard in the HARA process as mentioned above. Next, the definition of hazard in STPA includes both \"a system state or condition\" and \"a specific set of worst-case environmental conditions\" which describe the contexts of \"a system state or condition\", while in ISO26262 hazards are only \"potential source\" of harm [3; 4; 5; 6]. The meaning of \"harm\" in ISO26262 is similar to what \"loss\" means in STPA, but \"harm\" only means \"injuries or damage to the health of person\", while \"loss\" includes damage of property, pollution of environment, loss of mission, etc., besides human injuries or death. Although there is no definition of \"operating mode and operational situation\" in STPA, according to the description of these two concepts in ISO26262, we can infer that these two concepts can be included in the definition of hazard in STPA. So, if we limit the scope of \"loss\" in an \"accident\" in STPA to \"harms\" in ISO26262, an \"accident\" in STPA could be equivalent to a \"consequence of hazardous events\" in our study. As for safety goals in ISO26262, they could be equivalent to the system-level SCs in STPA, because they are similar in definition. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Foundations** & **ISO26262 HARA** & **STPA** \\ \hline \multirow{3}{*}{Objectives} & Identify and classify hazardous events. & Identify reasons for inadequate control or enforcement of safety related constraints. \\  & Formulate SGs and corresponding ASIL, & \\  & for each hazardous event & \\ \hline \multirow{2}{*}{Output Results} & Hazardous events and their classifications, & Accidents and associated hazards of a system, UCAs, SCs to be enforced \\  & SGs and associated ASILs & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._ \begin{table}
\begin{tabular}{c c c} \hline \hline
**Terminologies** & **STPA** & **ISO26262** \\ \hline \multirow{3}{*}{Accident} & Events leading to loss result from & \\  & lack of enough control and & Not specifically defined \\  & enforcement of SCs & \\ \hline \multirow{3}{*}{Hazard} & The combination of a system state & Potential source of physical injury or \\  & or set of conditions and a specific & damage to the health of persons \\ \cline{1-1}  & set of worst-case environmental & caused by malfunctioning behavior of \\ \cline{1-1}  & conditions, will lead to an accident & the item \\ \hline \multirow{2}{*}{Harm} & Not specifically defined & Physical injury or damage to the \\  & health of person \\ \hline \multirow{3}{*}{Failure} & A component’s (or system’s) & Termination of an intended behavior \\  & non-performance or inability to & of an element or an item due to a fault \\ \cline{1-1}  & perform as expected or designed. & manifestation \\ \hline \multirow{2}{*}{Operation Situations} & Not specifically defined & Scenarios that may occur within the \\  & & life of a vehicle \\ \hline \multirow{2}{*}{Operating modes} & Not specifically defined & Perceivable functional state of an item \\  & & or element \\ \hline \multirow{2}{*}{Hazardous event} & Not specifically defined & The result of integrating a hazard with \\  & & an operational situation \\ \hline \multirow{3}{*}{ASILs} & Not specifically defined & Levels used to specify safety measures \\  & & and necessary requirements of an \\ \cline{1-1}  & & element or item for avoiding \\ \cline{1-1}  & & unreasonable residual risk \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Key terminologies of STPA and ISO26262 concept phase. According to the analysis above, the differences between STPA and ISO26262 are mainly reflected in the fact that STPA covers a wider scope than ISO26262 in many key factors, such as hazard, accident, etc.