Web-scale data integration involves fully automated efforts which lack knowledge of the exact match between data descriptions. In this paper, we introduce schema matching prediction, an assessment mechanism to support schema matchers in the absence of an exact match. Given attribute pair-wise similarity measures, a predictor predicts the success of a matcher in identifying correct correspondences. We present a comprehensive framework in which predictors can be defined, designed, and evaluated. We formally define schema matching evaluation and schema matching prediction using similarity spaces and discuss a set of four desirable properties of predictors, namely correlation, robustness, tunability, and generalization. We present a method for constructing predictors, supporting generalization, and introduce prediction models as means of tuning prediction toward various quality measures. We define the empirical properties of correlation and robustness and provide concrete measures for their evaluation. We illustrate the usefulness of schema matching prediction by presenting three use cases: We propose a method for ranking the relevance of deep Web sources with respect to given user needs. We show how predictors can assist in the design of schema matching systems. Finally, we show how prediction can support dynamic weight setting of matchers in an ensemble, thus improving upon current state-of-the-art weight setting methods. An extensive empirical evaluation shows the usefulness of predictors in these use cases and demonstrates the usefulness of prediction models in increasing the performance of schema matching.