Text: Backfill Techniques Techniques used in cumulative case studies to collect information needed if the study is to be usable for aggregation; these techniques include, for example, obtaining missing information from the authors on how instances studied were identified and on the bases for instance selection.
Entailment: Backfill techniques can be used to gather information on a case study so that it can be analysed in conjunction with other studies.
Contradiction: Case studies performed by different researches using different techniques cannot be compared or combined to reach useful conclusions.