Diversity and Multi-Version Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 197

Figure 10. Model of dependencies 1 - 2

Figure 11. Model of dependencies 1 - 3

10 there is no connection between upper MC and
lower FC nodes, because this edge is dead. De-
pendency 4 between TP and MP diversity types
is reflected in Figure 12. Similar to all previous
diagrams, the split subgraph contains only one
node, in this case, TP.
To model dependency 5 according to the sub-
graph splitting algorithm, we need to split (dupli-
cate) the subgraph, which contains all nodes be-
tween TC and L (9 nodes, including TC, but
excluding L). Two edges and one node (marked
with crosses in Figure 13) are dead and should be
eliminated. The final diagram, which reflects
dependency 5, is shown in Figure 14.
For dependency 6, between MP and L diver-
sity types, node L should be split. This time, three

instances of L (one old and two new) are used
because three different “if - then” situations are
involved in this dependency. Two dead edges are
eliminated during the algorithm application. The
model for this dependency is shown in Figure 15.
To model dependency 7, the subgraph with
nodes between TC and TO is split. The process
of dead nodes and edges elimination has now
several cycles. The significant part of nodes and
edges are eliminated as shown in Figure 16 (marked
with black crosses for ingoing subgraph edges
and red crosses for outgoing subgraph edges). The
final model of the complete example is presented
in Figure 17.
The example provided here contains seven
diversity types and each type has from three to

Figure 12. Model of dependencies 1 - 4