According to an aspect, relation extraction using manifold models includes identifying semantic relations to be modeled in a selected domain. Data is collected from at least one unstructured data source based on the identified semantic relations. Labeled and unlabeled data that were both generated from the collected data is received. The labeled data includes indicators of validity of the identified semantic relations in the labeled data. Training data that includes both the labeled and unlabeled data is created. A manifold model is trained based on the training data. The manifold model is applied to new data, and a semantic relation is extracted from the new data based on the applying.