Abstract: Model-based safety analysis methods can improve the modeling and analysis capabilities of current complex safety-critical systems.At present,fault tree is widely used in system safety analysis and reliability analysis.Fault tree analysis (FTA) is a top-down deductive failure method,which analyzes undesired states in the system according to the fault tree.In the system engineering,the possible problems of the current system model can be determined as early as possible and avoided in time.The work of this paper is oriented to a type of system safety modeling language AltaRica in the aerospace field.Based on its semantic model GTS (guarded transition systems),a method for automatically constructing a system fault tree from the flattened GTS model is designed,which saves the time of artificial fault tree construction,and speeds up the progress of system analysis.According to the semantic rules of the AltaRica3.0 language,extracting the data of the flattened GTS model to construct instance objects,designing the GTS model division algorithm to obtain a set of independent GTS models and an independent assertion,constructing the reachability graph of the independent GTS through the adjacency matrix and obtaining the key event sequence,then,the indepen-dent GTS that has been processed is combined with the independent assertion,the state of the entire system and the sequence of key events are obtained through the assertion propagation algorithm,and the system fault tree is generated.Finally,an example system shows that the algorithm can effectively complete the automatic generation of fault trees from the flattened GTS model.

Key words: AltaRica, Assertion propagation algorithm, Division algorithm, Flattened GTS, FTA, Reachability graph