Auto-Tagging Content with Open Calais

Calais is a free web service from Clearforest, a Reuters company, that can perform semantic analysis on any English text. It uses natural language processing to extract concepts and relationships from the text. It’s been around for a few months, but there’s been very little developer activity around it, and even fewer completed applications using the technology.

Not finding any other work to build on, I wrote my own PHP class for extracting tags from content with Open Calais’ API. You can get the source and read more here. This class takes a block of text or HTML, sends it to Open Calais or parsing, and extracts all of the entities (things like peoples’ names, companies, technologies, etc.). It returns a multidimensional array organized by entity type.

There’s more Open Calais can do, but I hope this class contributes something to those PHP developers that’d like to start using it but had no place to start with the lightweight documentation and eerily quiet official forums. I plan on putting this class to work as an auto-tagging plugin for WordPress posts. I still need some time to figure out how to integrate that into the new authoring interface of WP 2.5, which this blog is now running on.

Posted on April 7, 2008 in Programming

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  • http://www.alistercameron.com/ Alister Cameron // Blogologist

    Dan,

    BRILLIANT!

    I have been waiting for someone to do this.

    Thanks SO much.

    Whatever else you can do with it… go for it!

    I think OC is one of the new gems of the Semantic Web and I can see it being so useful to WordPress in various ways.

    Thanks for getting the ball rolling :)

    -A

    PS. Did you win the money?!

  • http://www.dangrossman.info Dan

    Glad you like it! No, I didn’t enter the bounty program, so I wrote these plugins for free.

  • Clara

    I’m using WPMU
    I got message error like it..

    Parse error: syntax error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or ‘}’ in /home/XXX/public_html/wp-content/plugins/calais-auto-tagger/opencalais.php on line 17

    Hope you can make this plugin compatible with WPmu.

    Thx

  • http://www.hedgehogs.net Sam

    Hi Dan,

    we are using your opencalais PHP code.

    OpenCalais have upgraded their service and the code requires a little modification. We are initially just changing the URL and will carry out some investigation into the new categories.

    I just thought I would let you know.

    Cheers,

    Sam.

  • http://www.neerajkumar.name/ Neeraj Kumar

    google sent me here. this seems interesting. I am gonna try it out. will write about it if i find it useful :)