+ while(!isRVIBase(graph, base)) {
+ base = base.getParent(graph);
+ if(base == null) return null;
+ }
+ RVIPart part = getRVIPart(graph, variable);
+ if(part == null) return null;
+ RVI baseRVI = base.getPossibleRVI(graph);
+ if(baseRVI == null) return null;
+ return new RVIBuilder(baseRVI).append(part).toRVI();