DFTCalc Web-Tool
What does it do?
Summary
DFTCalc is a tool for efficient Fault Tree Analysis. It takes as input a DFT (dynamic fault tree) in Galileo-format and a set of mission times, and computes the system unreliability for each mission time, i.e. the probability that the system fails within the mission time. Further it is capable of computing the mean time to failure (MTTF), i.e. the expected time that the system will fail.
Usage
To experiment with the DFTCalc tool you can use this web-based version. Just provide a DFT in Galileo-format in the text area , or choose one of the existing examples. There are three different objectives to compute:
- Unreliability in interval [0,T]
- provide a set of missions times, either by:
- enumerating the values
- or providing lower and upper bounds (optional step increment)
- choose between MRMC and IMCA
- provide a set of missions times, either by:
- Unreliability in interval [T1,T2]
- obtain the probability that the system don't fail before T1 but in the interval [T1,T2] by:
- providing a lower bound T1 > 0
- and an upper bound T2 > T1
- For this computation, IMCA is used.
- Mean time to failure (MTTF)
- Obtain the systems mean time to failure and optionally
- provide values for a plot -- longest mission time, step value -- to override the defaults
- For this computation, IMCA is used.
Click on the 'Show Result' button (to obtain textual output)
or the 'Show Plot' button (to obtain a graph),
or the 'Show Plot and store data set' (to obtain a graph, and store its data for later use in a combined plot).
When you click on 'Permalink', what you entered in the form is stored on the server, and a URL is generated that, when you access it, will give you the form, populated with the stored form data. You can store this URL, or mail it to others, to allow them to repeat what you did.
To reduce the computation time of subsequent queries on a given DFT (with given evidence), intermediate computation results are cached for you on the server (they are removed when your session expires).
Plotting
Each time that you click on 'Show Plot and store data set', you will not only get the graph that 'Show Plot' gives you too, but also an additional check-button.
When you check one or more of these check-buttons, and click on 'Plot selected data sets in combined plot' you will get a single plot, created from the selected data sets.
If you specified a name for a data set, this name will be used in the combined plot to identify the curve of that data set.
When you check one or more of these check-buttons, and click on 'Download selected data sets', a gzip-ed tar archive will be created from the data sets that you selected, and a link to download this archive will be shown.
Try, for example, to create a plot of MTTF values for 'dft test1', using scenarios 'without evidence, with given plot parameters', and 'failed B', 'failed C' and 'failed B and failed C'.
Additional settings
- Evidence: list the names of the components that have failed.
- Error bound: Error bound to be used in the computations.
- Prob: indicate whether in case of non-determinism, minimal or maximal probability must be computed.
- Time: indicate whether in case of non-determinism, minimal or maximal expected time (for MTTF) must be computed, or whether the setting given for 'Prob' must be used.
- Version: choose one of the available dftcalc versions.
- Verbosity: indicate level of verbosity (dftcalc version information is shown for any non-off level).
- Coloured output: indicate whether or not to use coloured text in the verbose output.
- No pointmarks: indicate whether to omit the point marks in plots.