A method and system are disclosed that enable a user to search a large collection of structured and unstructured documents using semantic concepts that the system provides to them, to search the most relevant business activity first, and then using one of the business activities as the additional context to search for specific document or documents that are most relevant. One aspect of the invention provides a methodology to perform concept-based structured search over document collections to obtain search results as business activities and associated relevant documents using the business activity context. The document collections are obtained by aggregating documents corresponding to a business activity. The instances are extracted from the document collections together with any concept-relationship specific heuristics in that domain. Another aspect of the invention enables the enterprise user to enter concepts and instances that define the search parameters using a structured user interface.