14. A system for visualizing content change of a data collection over time, comprising: a processor; a document pre-processing module operable to execute on the processor, and further operable to extract text and associated meta data from a collection of documents; a topic summarization module operable to automatically extract a set of topics based on the extracted text and associated meta data; a topic segmentation module operable to split a topic in the set of topics into multiple, non-overlapping temporal segments, wherein content for visualization is generated; and a text visualization module operable to generate a time-based, interactive visual text summary based on the content, wherein the topic segmentation module is operable to generate temporal and visual constraints, the topic segmentation module further operable to derive from the collection of documents a set of document clusters that satisfy the temporal and visual constraints, a document cluster in the set of document clusters identified with a sub-topic, the topic segmentation module further operable to determine a temporal segment boundary associated with said document cluster, wherein the temporal segment boundary identifies a temporal segment for the sub-topic, the topic segmentation module further operable to select a set of representative keywords from the document cluster to summarize the temporal segment.
18. The system of claim 14 , wherein the topic segmentation module determines a temporal segment boundary by at least: sorting all documents in the set of document clusters on a timeline based on time stamps associated with the documents; employing a sliding window of size N to examine N documents at a time; identifying one or more documents from the examined documents whose cluster labels do not conform to a main cluster; and reassigning the identified one or more documents to the main cluster within the sliding window, wherein the temporal boundary is determined in response to identifying a change of cluster labels between two adjacent documents on the time line.