Friday 27 May 2011

Parsing the Enron email dataset using Tika and Hadoop

In order to parse a large collection of emails, such as the Enron Email Dataset, we might choose to use Apache Hadoop, a scalable computing framework, and Apache Tika, a content analysis toolkit. This can be done easily with Behemoth, an open source platform for large scale document analysis developed by DigitalPebble. For more details of Behemoth, see the Behemoth Tutorial.

Using the August 21, 2009 version of the dataset, the first step is to use Behemoth's CorpusGenerator to create a corpus of BehemothDocuments from the Enron Dataset in HDFS. A BehemothDocument is the native object used by Behemoth. At ingest, it contains the original document, its content type and URL. After processing by a Behemoth module, it also contains the extracted text, additional metadata and annotations created about the document.

Once the dataset has been ingested, the next step is to use the Behemoth Tika module to create a Hadoop Map/Reduce job to extract the contents of the emails and metadata about them. Using Apache Tika 0.9, 5% of the documents fail to parse correctly. However using the latest version of Tika (Tika-1.0-snapshot revision 825923) only 0.2% documents fail.

One way to investigate why parsing is failing is by looking at the user logs generated within Hadoop, which contain details of the exceptions causing the failing documents. An alternative way is to write a custom reducer that sorts the exceptions thrown by Tika, with the exception stack being used as a key and a document URL as values. With Tika revision 825923, four exceptions are thrown, caused by two underlying problems: excessive line lengths of over 10,000 characters, the current default in the Tika mail parser, and malformed dates. The first problem can be solved by increasing the maximum line length in a MimeEntityConfig object and then modifying TikaProcessor to pass it into the ParseContext.

As for the second problem, currently the mail parser in Tika performs strict parsing, i.e. parsing a document fails when parsing a field fails. Tika-667 contains a contribution that makes it possible to turn off strict parsing, so some data can still be extracted from the emails with the malformed dates. This can also be configured via MimeEntityConfig. When these changes are incorporated, all documents are processed correctly.

Saturday 7 May 2011

Nutch talk at Berlin Buzzwords 2011

I'll be giving a talk on Apache Nutch at Berlin Buzzwords.

This talk will give an overview of Apache Nutch. I will describe its main components and how it fits with other Apache projects such as Hadoop, Lucene, SOLR, Tika or HBase. The presentation will contain examples of real-case uses.

The second part of the presentation will be focused on the latest developments in Nutch and the changed introduces by the forthcoming version 2.0.

Tuesday 22 March 2011

Search for US properties with SOLR and Maptimize

Our clients 5k50 have recently opened a preview of their real-estate search system which is based on Apache SOLR and Maptimize. Maptimize is a very nice tool which which manages the display of data on Google Maps by merging markers which are geographically close together.

We initially audited the existing SOLR setup then redesigned it to add more functionalities and optimise the search speed.  The search itself is an interesting mix of map-driven filtering with SOLR queries and faceting. Any changes to the map (click on a cluster, zoom in/out) are reflected in the search results and facets and vice-versa.

Navia is a nice showcase for some of the most commonly used features of SOLR (i.e. faceting, more-like-this, autocompletion) and has a great identity thanks to its mix of geo and text search.  It is currently in beta mode so we can expect a few more improvements over the next few weeks.

And please feel free to give it a try so that we can get plenty of data on the performance :-)

Saturday 19 March 2011

DigitalPebble is hiring!

We are looking for a candidate with the following skills and expertise :
  • strong background in NLP and Java
  • GATE, experience of writing plugins and PRs, excellent knowledge of JAPE
  • IE, Linked Data, Ontologies
  • statistical approaches and machine learning
  • large scale computing with Hadoop
  • knowledge of the following technologies / tools : Lucene, SOLR, NoSQL, Tika, UIMA, Mahout
  • good social and presentation skills
  • good spoken and written English, knowledge of other languages would be a plus
  • taste for challenges and problem solving

    DigitalPebble is located in Bristol (UK) and specialises in open source solutions for text engineering.

    More details on our activities can be found on our website. We would consider candidates working remotely with occasional travel to Bristol and our clients in UK and Europe. Being located in or near Bristol would be a plus.

    This job is an opportunity to get involved in the growth of a small company, work on interesting projects and take part in various Apache related projects and events. Bristol is also a great place to live.

   Please send your CV and cover letter before the 15th April 2011 to

    Best regards,

    Julien Nioche

Monday 21 February 2011

Watson, the computer Behemoth in Jeopardy!

Alex Popescu's excellent blog mentioned the DeepQA project and IBM's supercomputer Watson. Watson's recent appearance on the US TV show Jeopardy!. Interestingly, DeepQA uses both Apache Hadoop and UIMA to analyse large volumes of documents to build DeepQA's knowledge-base.

As explained in
"To preprocess the corpus and create fast run-time indices we used Hadoop. UIMA annotators were easily deployed as mappers in the Hadoop map-reduce framework. Hadoop distributes the
content over the cluster to afford high CPU utilization and provides convenient tools for deploying, managing, and monitoring the corpus analysis process."
which is exactly what Behemoth does (how very reassuring!).

The article also mentions UIMA-AS and it is not entirely clear what part of the system uses what : is UIMA-AS used for the runtime analysis of the questions and Hadoop for the background learning?

Would be interesting to know what sort of UIMA annotators were used internally for the analysis of the text and, more importantly from Behemoth's point of view, whether it could have been used for this project and/or what features would have been required to get it to work on DeepQA.

Friday 21 January 2011

BerlinBuzzwords 2011

There is a CFP for BerlinBuzzwords 2011 which will be on 6/7 June. As the website says :

I presented Behemoth there last year and really enjoyed the conference. High quality talks, fantastic atmosphere and great exchanges with fellow open source committers. I really recommend it and will definitely try to go next year and probably give a short talk about Nutch 2.0, GORA or maybe give a quick update about Behemoth.

Tuesday 14 December 2010

Module management with IVY

I've just recently some massive changes to the way we manage the code in Behemoth. Prior to that, we had a single src directory containing the various resources for using Tika, GATE, UIMA or Nutch within Behemoth. That worked fine but had a few drawbacks, mostly that we ended up with an enormous job file containing all the dependencies for all the modules. In practice most people use Behemoth with only one type of resource but not more (e.g. UIMA vs GATE).

There was also a concept of Sandbox in Behemoth which I mentioned a couple of times. The idea was to allow external contributions based on Behemoth's core and keep them separated.

Before the change, Grant Ingersoll  (who has been using Behemoth to parse a large amount of documents with Tika) had made a contribution which allowed to generate a jar file for the Behemoth core classes only. In his case, he wanted to be able to play with the Behemoth output without having to deal with a mega large job file. The modularisation of the code allows to do just that but extends the principle to all the modules.

Here is how it now works. I split the code into several modules managed by Apache Ivy (by simply following the tutorials) e.g. core, uima, gate, tika, solr, etc... Most non-core modules have at least a dependency to core as well as the external jars that they require. All modules have the same ant targets and the main ant build script at the root of the project allows to resolve the dependencies, compile, test for each module. We now get separate jars file for each module (which Grant needed for the core) but also publish these jars locally via Ivy so that the other modules can rely on them.

Building a job file is done on a per-module basis, by going into a module's root directory and calling 'ant job'. The resulting job file should then contain all the dependencies for this module and can be used in Hadoop, as usual.

This new organisation of the code is definitely cleaner, leaner and easier to maintain or extend. If for instance a user want to build a process which combines the functionalities of two or more modules, it is just a matter of creating a new module with the right dependencies to the modules used (say for instance Tika + Gate + SOLR), write a custom Job and Mapreduce class and generate a job file as described above.

The concept of sandboxes is now deprecated, as they are now modules, just like everything else. The beauty being that - if the Behemoth modules are published and accessible publicly, one could simply point to them in the Ivy config of a local module and build a Behemoth application with a minimal amount of code.

Isn't that just fun!