Heterogeneity of information sources: Data may originate at a few authoritative sources, or alternatively, every participant might be allowed (or expected) to contribute data to the community. The level of heterogeneity of the data influences the degree to which a system can ensure uniform, global semantics for the data. A P2P system might impose a single schema on all participants to enforce uniform, global semantics, but for some applications this will be too restrictive. Alternatively, a limited number of data sources and schemas may be allowed, so traditional schema and data integration techniques will likely apply (with the restriction that there is no central authority)
