In heterogeneous data sources integration systems, there can be many special limited access patterns to access interface of data sources, i.e., binding patterns impose a restriction that one or more input attributes must have a binding, and also restrict the output attributes that are projected. Constrained by the expressiveness of the access interface, users often have difficulty in articulating a precise query over the data sources. In this paper, we propose a data model for data sources' capability object integration (COIM) to capture a rich variety of query-processing capabilities and present algebra to compute the set of mediator-supported queries based on the capability limitations of the sources they integrate. By computing mediator query capabilities and representing them in the same way as those of data sources, we enable mediators to be used by other mediators as well as other applications, and we also make it easier for end users to know in advance which mediator queries are feasible.