Introductory article
Measuring remaining mission capability
A plain-language introduction to the metric S(t) and its limitations.
From resource to mission
The dissertation connects four levels: resources → services → functions → mission. A resource failure propagates through the services and functions that depend upon it, potentially limiting mission capability.
Structural availability is not the same as actual quality: a configuration may contain the required modules but still perform poorly because its resources have degraded.
The survivability measure
\[
S(t)=\sum_{j=1}^{m}\alpha_j\,\delta_j(cfg(t))\,\varphi_j(t,cfg(t))
\]
Here:
- S(t) is survivability at time t, between 0 and 1;
- αj is the mission priority of function j;
- δj indicates whether the function is enabled;
- φj describes its integrity given the available resources.
Three different quantities
\[
0\le S(t)\le\overline{S}(cfg)\le\Phi(cfg)\le 1
\]
Φ(cfg) is structural function availability, S̄(cfg) is the configuration's nominal upper bound, and S(t) is its current actual survivability. They must not be confused.
For detailed conditions, see capability and admissibility.