Ontology matching is the process of finding correspondences between entities from different ontologies. Whereas the field has fully developed in the last decades, most existing approaches are still limited to pairwise matching. However, in complex domains where several ontologies describing different but related aspects of the domain have to be linked together, matching multiple ontologies simultaneously, known as holistic matching, is required. In the absence of benchmarks dedicated to holistic matching evaluation, this paper presents a methodology for constructing pseudo-holistic reference alignments from available pairwise ones. We discuss the problem of relaxing graph cliques representing these alignments involving a different number of ontologies. We argue that fostering the development of holistic matching approaches depends on the availability of such data sets. We run our experiments on the OAEI Conference data set.