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From <Armin.Weg...@bka.bund.de>
Subject AW: HashMap as type feature
Date Thu, 17 Oct 2013 14:43:53 GMT
Hi Thomas,

thanks for your answer. Using HashMap, does the n-th element of keySet() always corresponds
to the n-th element of values()? Is this a defined behavior in Java?


-----Urspr√ľngliche Nachricht-----
Von: Thomas Ginter [mailto:thomas.ginter@utah.edu] 
Gesendet: Mittwoch, 16. Oktober 2013 18:53
An: <user@uima.apache.org>
Betreff: Re: HashMap as type feature


Our team does this with an annotation type designed to store feature vectors for Machine Learning
applications.  In this case we use a StringArray feature for the keys and a StringArray feature
for the values.  The StringArrays are pulled from a HashMap<String, String> vector variable
and inserted into the features with the following code:

int size = vector.size();
StringArray keys = new StringArray(jcas, size); StringArray values = new StringArray(jcas,
size); keys.copyFromArray(vector.keySet().toArray(new String[size]), 0, 0, size); values.copyFromArray(vector.values().toArray(new
String[size]), 0, 0, size);

Retrieving the values is fairly straightforward.  If you are using a static annotation type
it can be as simple as:

StringArray keys = vector.getKeysArray();

If you parameterize our annotation type in the annotator you can use the name of the feature
to get a Feature object reference then pull the StringArrays like so:

Type annotationTypeObj = aJCas.getRequiredType("com.my.Annotation"); //parameter is the canonized
name of the Annotation type Feature keyFeature = annotationTypeObj.getFeatureByBaseName("keyFeatureName");
//the actual name of the feature storing the key StringArray reference Feature valuesFeature
= annotationTypeObj.getFeatureByBaseName("valuesFeatureName"); //the name of the values feature

//Get a list of the annotation objects in the CAS then iterate through the list, for each
annotation 'a' do the following to retrieve the keys and values

StringArray keys = (StringArray) vector.getFeatureValue(keysFeature);
StringArray values = (StringArray) vector.getFeatureValue(valuesFeature);

If necessary you can retrieve a String[] from the StringArray FeatureStructure by calling
the .toArray() method such as:

String[] keysArray = keys.toArray();

Let me know if you have any questions.


Thomas Ginter

On Oct 16, 2013, at 9:55 AM, Dr. Armin Wegner <arminwegner@googlemail.com<mailto:arminwegner@googlemail.com>>


I'd like to have a type feature that is a list of key-value pairs. The number of pairs is
unknown. What's best for this? Is it even possible?


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