9. Safety Architectural Patterns - Research - Mälardalens högskola

only for safety parts of the automations and critical parts of the system. More to this, some ofthe attributes and properties are very complex to express in temporal logics and sometimeerror prone as well. Most of the practitioners and verification users are also not logiciansalthough they know very well about the properties which they want to verify but cannotexpressed it in good logic and formal language.The detail and the example of these patterns classification can be described in below:Static safety requirementsIt includes the property that an operation should hold that property as true in the wholeoperational model. Traffic light crossing requirement can be applied here when it is notpermitted that a green light would be turned on for main road and at the same time for sideroads.Dynamic safety requirementsThese requirements include that a property must be true in some of the states while in otherstates it should be false. The permission to open the traffic gates is given only when the trainhas passed.Safety requirement about general access guaranteeThese requirements are related to all model states. Emergency break is one of theserequirements where the emergency break should be actuated or accessible in all situations.Safety requirements with Temporal DependenciesIn these requirements the temporal dependencies exist between the event of detected defectand the action against it. It requires when a specific statement should begin and for how longit should remain valid. Pneumatic break is one of such example when the defect is detectedsoftware control system has to be switched off after a certain delay.Safety requirements about chronological successionIn these requirements the property is dependent on the occurrence of other properties. It hasthe proposition of “if then” and it tells how long exactly the predecessor and from whenexactly the successor event is permitted to be valid.Safety requirement about duration of validityThese requirements refer to the duration respectively ending of the validity of a propertywhich is actually dependent on the other properties. Like, the flow of water is only possiblewhen the temperature reaches to a certain level in the pipeline.Safety requirement about beginning of validityThese requirements are about the beginning of validity of a property, which is dependent onthe other properties too. An example can be “The safeguard of a level crossing is onlypermitted to be terminated, strictly after the railroad crossing has been completely vacated ifthe train had passed.“Safety requirement about beginning and duration of validity39