1. A system comprising: at least one processor; and a memory device operatively connected to the at least one processor; wherein, responsive to execution of program instructions accessible to the at least one processor and configured to automatically discover at least one text-based pattern in at least one text corpus, the at least one processor is configured to: issue a query of the text corpus to extract at least one context string comprising a sequence of text from the text corpus, the sequence of text identified using a positional relationship to at least one text annotator corresponding to a text entity of interest included in text of the at least one text corpus; analyze the at least one context string to produce at least one sequence representing a text-based pattern of the context string; determine at least one semantic sequence signature for the context string from the at least one sequence which identifies the context string; and thereupon use the at least one semantic sequence signature to automatically group semantically similar context strings of the text corpus.