Abstract: A method for searching for documents may include receiving information for a source document, the information including at least one topic and a weight for each topic, where the topic relates to content of the source document, and the weight represents how strongly the topic is associated with the source document, accessing an index containing topics and references to documents containing those topics and selecting a set of documents, where each document in the set is associated with at least one of the topics in the source document, generating similarity scores based on the weight of a topic in the source document and a weight of the same topic in each document within the set of documents having that topic, and selecting a subset of documents from the set of documents based on the similarity scores.

Abstract: A method for indexing documents may include receiving a first set of topics relating to a text of a document and a weight for each topic in the first set, where the weight represents how strongly the topic is associated with the document, and generating an update to an index by inserting a reference to the document for each of the topics in the first set. A second set of topics relating to the text of the document and a weight for each topic in the second set may be received. An update to the index may be generated by inserting the reference to the document for topics in the second set that are not in the first set and removing the reference to the document for topics in the first set that are not in the second set.