SOLR and Natural Language Parsing - Can I use it?

You can actually configure Solr to use NLP algorithms both when indexing documents and at search time. The first phase (indexing time) can be done using/writing Solr UpdateRequestProcessor plugins for analyzing fields texts while the second phase can be implemented writing a custom QParserPlugin which analyzes the query hit by the user. I've presented an approach for implementing natural language search in Solr at Lucene Eurocon 2011 which takes advantage of Apache UIMA for running (open source) NLP algorithms. You can take a look at the slides and at the video of the talk. Hope this helps. Tommaso

I guess you can use Solr and combine it with other tools. Tokenization, stop word removal, stemming, and even synonyms come out of the box with Solr. If you need named entity recognition or base noun-phrase extraction, you need to use OpenNLP or an equivalent tool as a pre-processing stage. You will probably need term vectors for your retrieval purposes. Integrating Apache Mahout with Apache Lucene and Solr may be useful as it discusses Lucene and Solr integration with a machine learning (including recommendation) engine. Other then that, feel free to ask further more specific questions.