Methods for Information Extraction, Search, and Structured Representation of Text Data

System and methods for creating structured or semi-structured representations of information extracted from unstructured text data sources are described. In some embodiments, without requiring a predefined target data structure, the methods identify the grammatical and semantic attributes and context information in a text content, and create object-properties association data as knowledge and information extracted from the unstructured data, and represent such information in a structured or semi-structured format to facilitate search and trend analysis. In some other embodiments, the methods identify the types of information contained in the unstructured data, and for a pre-defined target information type, the methods identify the context and content of the portion of the text that represents the target information type, and extract the text, attach a tag or label to the extracted text, and store or display the data in a database table format or xml format for further pattern and trend analysis. Applications of the present system and methods include effectively analyzing user-generated contents such as customer feedback, reviews, comments, technical support forum messages, resume or job description documents, and other types of text contents.