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Chalk

Author: Jason Baldridge (jasonbaldridge@gmail.com)

Introduction

Chalk is a library for natural language processing (NLP). The present version (1.0) is pretty much an exact copy of Apache OpenNLP v1.5.3 (opennlp.apache.org), except that "chalk" has been substituted for "opennlp" in the package names, and SBT is used to configure and build the project. Why do this? Basically, I would like to be able to change and extend OpenNLP using Scala and Akka, and I wanted to release the first version as essentially unchanged from OpenNLP. That makes the history of changes easier to track, and it might provide some useful examples for making Java-to-Scala transitions. Ultimately, I see this diverging substantatially from OpenNLP, and no attempt for compatibility will be made as of this breaking point. (I think the OpenNLP team is great and as one of the co-creators of OpenNLP, I am still very much interested in seeing OpenNLP evolve and improve. However, I really want to explore some ideas using Scala and Akka and figured this was the most straightforward and nimble way to move forward on it.)

I've called this Chalk because my son has a stuffed elephant that he named Chalk. "Chalk" obviously has a great connection to writing (and thus text processing). Of course, it also follows the what-your-kid-called-his-elephant naming convention precedent established with Hadoop. :)

In addition to OpenNLP, there are two other related projects. One is Scalabha (https://github.com/utcompling/Scalabha), which I started as a package for teaching Scala in computational linguistics projects, and which I may pilfer as Chalk develops. The other is Breeze, which is a Scala-based machine learning and NLP project that I've been peripherally involved with. It's a great and very general library; ultimately, I expect to bring Breeze in as a dependency and then Chalk will in some respects be an example of building an NLP library on top of the core capabilities provided by Breeze.

Using Chalk

In SBT:

libraryDependencies += "com.jasonbaldridge" % "chalk" % "1.0"

In Maven:

<dependency>
   <groupId>com.jasonbaldridge</groupId>
   <artifactId>chalk</artifactId>
   <version>1.0</version>
</dependency>

Requirements

Configuring your environment variables

The easiest thing to do is to set the environment variables JAVA_HOME and CHALK_DIR to the relevant locations on your system. Set JAVA_HOME to match the top level directory containing the Java installation you want to use.

Next, add the directory CHALK_DIR/bin to your path. For example, you can set the path in your .bashrc file as follows:

export PATH=$PATH:$CHALK_DIR/bin

Once you have taken care of these three things, you should be able to build and use Chalk.

Building the system from source

Chalk uses SBT (Simple Build Tool) with a standard directory structure. To build Chalk, type (in the $CHALK_DIR directory):

$ ./build update compile

This will compile the source files and put them in ./target/classes. If this is your first time running it, you will see messages about Scala being downloaded -- this is fine and expected. Once that is over, the Chalk code will be compiled.

To try out other build targets, do:

$ ./build

This will drop you into the SBT interface. To see the actions that are possible, hit the TAB key. (In general, you can do auto-completion on any command prefix in SBT, hurrah!)

To make sure all the tests pass, do:

$ ./build test

Documentation for SBT is at http://www.scala-sbt.org/

Note: if you have SBT already installed on your system, you can also just call it directly with "sbt" in CHALK_DIR.

Trying it out

Assuming you have completed all of the above steps, including running the "compile" action in SBT, you should now be able to try out some examples. There is no documentation specific to Chalk at this time, but you should be able to follow the OpenNLP documentation:

http://opennlp.apache.org/documentation/1.5.2-incubating/manual/opennlp.html

However, you'll need to substitute 'chalk cli' for 'opennlp' in that manual. Here's an example to do sentence detection.

    $ echo "Pierre Vinken, 61 years old, will join the board as a nonexecutive director Nov. 29. Mr. Vinken is chairman of Elsevier N.V., the Dutch publishing group. Rudolph Agnew, 55 years old and former chairman of Consolidated Gold Fields PLC, was named a director of this British industrial conglomerate." > input.txt

    $ wget http://opennlp.sourceforge.net/models-1.5/en-sent.bin

    $ chalk cli SentenceDetector en-sent.bin < input.txt 
    Loading Sentence Detector model ... done (0.099s)
    Pierre Vinken, 61 years old, will join the board as a nonexecutive director Nov. 29.
    Mr. Vinken is chairman of Elsevier N.V., the Dutch publishing group.
    Rudolph Agnew, 55 years old and former chairman of Consolidated Gold Fields PLC, was named a director of this British industrial conglomerate.



    Average: 1500.0 sent/s 
    Total: 3 sent
    Runtime: 0.0020s

Questions or suggestions?

Email Jason Baldridge: jasonbaldridge@gmail.com

Or, create an issue: https://github.com/jasonbaldridge/chalk/issues

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