5 The Recommender Controller

5.1 Web-based Recommenders' Evaluator

By access to http://localhost:8080/<yourApplication>/recommender/evaluator in your browser, you will see a screen similar to the following image:

Start running the evaluation process by click on "Run Evaluator" link.

5.2 Web-based Recommender

By access to http://localhost:8080/<yourApplication>/recommender/settings in your browser, you will see a screen similar to the following image:

After fill-in all required fields, click on "Submit" button to see the recommendations.

You can checked the check box of "Enabled debug?" to see the recommendation results with more debugging information.

Recommendations Without Debug-enabled

Recommendations With Debug-enabled

5.2.1 REST Support

XML Recommended Items

http://localhost:8080/<yourApplication>/recommender.xml?userID=1&howMany=20&
r=1&p=true&s=PearsonCorrelation&w=true&n=4

You will see XML message similar to the below display in your browser

<recommendedItems>
  <item>
    <value>5.0</value>
    <id>104</id>
  </item>
  <item>
    <value>4.0</value>
    <id>106</id>
  </item>
</recommendedItems>

If some error occur, you will see XML message similar to the following:

<error>
  <message>Recommender cannot be blank.</message>
</error>

JSON Recommended Items

http://localhost:8080/<yourApplication>/recommender.json?userID=1&howMany=20&
r=1&p=true&s=PearsonCorrelation&w=true&n=4

The URL above is identical to the XML request, except it invoke to recommender.json instead of recommender.xml.

You will see JSON message similar to the below display in your browser

{"recommendedItems":[{"value":5,"id":104},{"value":4,"id":106}]}

If some error occur, you will see JSON message similar to the following:

{"error":{"message":"Recommender cannot be blank."}}

Usage

http://localhost:8080/<yourApplication>/recommender.[json|xml]?
userID=[Long]&howMany=[Integer]&r=[1|2|3]&p=[true|false]&
s=[PearsonCorrelation|EuclideanDistance|LogLikelihood|TanimotoCoefficient]&
w=[true|false]&n=[Integer|Double]

1. File extension: recommender.xml for XML request, recommender.json for JSON request.
2. userID: Specify user ID. in numeric value as java.lang.Long type.
3. howMany: Specify expected number of recommendations return in numeric value as java.lang.Integer type.
4. r: Specify recommender. Valid values: 1, 2 or 3 (1. user-based, 2. item-based or 3. slope-one).
5. p: Specify "has preference value". Valid values: true or false.
6. s: Specify similarity metric. Valid values: PearsonCorrelation, EuclideanDistance, LogLikelihood or TanimotoCoefficient.
7. w: Specify whether weighting is enabled. Valid values: true or false. Applicable to 'PearsonCorrelation' or 'EuclideanDistance' similarity metric or Slope-one recommender only.
8. n: Specify whether fix-size neighborhood or threshold-based neighborhood when user-based recommender is selected in r above. Integer value for fix-size neighborhood such as 4 and Double value (< 1.0) for threshold-based neighborhood such as 0.5.

Item 4 to 8 above need to be specified only when mahout.recommender.mode = 'input' in Config.groovy file.