MentalProcedureActivationTimeBranches.txt

Purpose

The MentalProcedureActivationTimeBranches.txt input file allows multiple accident sequence branches to be generated when a memorized mental procedure is activated. Following activation of a mental belief (defined in KB_OAT(ODM)_HardWired_Diagnosis.txt), the operator will implement the associated mental procedure after an activation time delay has elapsed.

To capture the uncertainty and crew-to-crew variability in the time delay between belief activation and mental procedure execution, the activation delay is modeled with a three-parameter Weibull probability density distribution.

• When only one mental procedure activation time branch is generated, the activation time delay equals the mean value of the Weibull distribution.
• When more than one branch is generated, the probability distribution is partitioned into segments and the time delay for each sequence branch is determined by the mean value over the associated partition.

Weibull Partition Method (Figure 18, Equation 10)

The partition boundaries are determined by dividing the probability range of the Weibull cumulative distribution function (CDF) into a number of segments equal to the number of desired branches. Each branch receives an equal probability mass from the CDF. For example, five branches produce five equal-probability segments; each partition boundary falls at a CDF increment of 0.2.

The activation time for each branch is the mean activation time over its associated partition. For the first and second partitions (Equation 10):

$$t_{\text{partition 1}}=\frac{{\int }_0^{t_{1\text{-}2}}{t}_{\text{delay}}p(t_{\text{delay}})dt}{{\int }_0^{t_{1\text{-}2}}p(t_{\text{delay}})dt}$$$$t_{\text{partition 2}}=\frac{{\int }_{t_{1\text{-}2}}^{t_{2\text{-}3}}{t}_{\text{delay}}p(t_{\text{delay}})dt}{{\int }_{t_{1\text{-}2}}^{t_{2\text{-}3}}p(t_{\text{delay}})dt}$$

Where $t_{1\text{-}2}$ and $t_{2\text{-}3}$ are the partition boundaries between partitions 1 and 2, and partitions 2 and 3, respectively. In a five-branch case, $F(t_{1\text{-}2})=0.2$ and $F(t_{2\text{-}3})=0.4$, where $F(t)$ is the cumulative probability density function. This approach captures the probabilistic nature of the mental procedure activation time while maintaining reproducibility of the analysis.

INFO

The first branch represents the shortest activation time delay and the last branch represents the longest activation time delay.

Input File Format

Each entry is one line — mental_belief mental_procedure number_of_branches (matching the shipped BV4 file; the parser is token-based, so line breaks and other whitespace are interchangeable):

Instinctive_Response_Activation_Time_Branches    number_of_items
mental_belief_1    mental_procedure_1    number_of_branches_1
.
.
mental_belief_n    mental_procedure_n    number_of_branches_n

Parameter Descriptions

Parameter	Type	Description	Example Value
number_of_items	Integer, ≥ 0	Number of mental procedure activation time branching events in the file. Setting to 0 disables all branching without requiring deletion of entries.	2
mental_belief	String	Name of the mental belief that activates the branching event. Must match a valid mental_belief_name in KB_OAT(ODM)_HardWired_Diagnosis.txt.	SG_A_SGTR_Isolate_AFW
mental_procedure	String	Name of the mental procedure to branch on. Must match a valid procedure_name in Procedures.txt with the prefix MPBG_.	MPBG_SG_A_Isolate_AFW
number_of_branches	Integer, ≥ 1	Number of event sequence branches to generate. With 1, no branching occurs — the activation delay is the mean of the Weibull distribution.	3

TIP

Setting number_of_items to 0 disables all branching events without needing to delete entries. To activate only one branching event, move it to the top of the list and set number_of_items to 1. Only the first number_of_items entries are read — the BV4 reference file ships with a count of 0, so the example rows listed below its header are inert.

Execution

Each alternative defined here is opened as a child sequence that restarts from the branch point with that alternative applied. See How a Branch Alternative Executes.

Sample Input

Instinctive_Response_Activation_Time_Branches    2
SG_A_SGTR_Isolate_AFW     MPBG_SG_A_Isolate_AFW         3
SG_A_FWRV_Manual_Mode     MPBG_SG_A_FWRV_Manual_Mode    5

Sample Explanation

• When the SG_A_SGTR_Isolate_AFW mental belief is activated, 3 activation time branches are generated prior to initiation of the MPBG_SG_A_Isolate_AFW mental procedure. Each time branch corresponds to a different partition of the activation time probability distribution. The first branch represents the shortest activation time delay and the third branch represents the longest.

• When the SG_A_FWRV_Manual_Mode mental belief is activated, 5 timing branches are generated prior to initiation of the MPBG_SG_A_FWRV_Manual_Mode mental procedure. The first branch represents the shortest activation time and the fifth represents the longest.