diff --git a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommender.java b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommender.java
index 6ea8b5a60f0..0a773f7680a 100644
--- a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommender.java
+++ b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommender.java
@@ -40,6 +40,8 @@
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
+import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
 
@@ -65,6 +67,7 @@
 import de.tudarmstadt.ukp.inception.recommendation.api.recommender.RecommenderContext.Key;
 import de.tudarmstadt.ukp.inception.recommendation.imls.stringmatch.span.gazeteer.GazeteerService;
 import de.tudarmstadt.ukp.inception.recommendation.imls.stringmatch.span.gazeteer.model.GazeteerEntry;
+import de.tudarmstadt.ukp.inception.recommendation.imls.stringmatch.span.trie.KeySanitizerFactory;
 import de.tudarmstadt.ukp.inception.recommendation.imls.stringmatch.span.trie.Trie;
 import de.tudarmstadt.ukp.inception.recommendation.imls.stringmatch.span.trie.WhitespaceNormalizingSanitizer;
 import de.tudarmstadt.ukp.inception.rendering.model.Range;
@@ -87,6 +90,11 @@ public class StringMatchingRecommender
 
     private final GazeteerService gazeteerService;
 
+    private final KeySanitizerFactory keySanitizerFactory;
+
+    private Pattern excludePattern;
+    private String excludePatternError;
+
     public StringMatchingRecommender(Recommender aRecommender,
             StringMatchingRecommenderTraits aTraits)
     {
@@ -100,6 +108,19 @@ public StringMatchingRecommender(Recommender aRecommender,
 
         traits = aTraits;
         gazeteerService = aGazeteerService;
+        keySanitizerFactory = WhitespaceNormalizingSanitizer.factory();
+
+        if (traits != null && traits.getExcludePattern() != null) {
+            try {
+                excludePattern = Pattern.compile(traits.getExcludePattern());
+            }
+            catch (PatternSyntaxException e) {
+                excludePatternError = e.getMessage();
+            }
+        }
+        else {
+            excludePattern = null;
+        }
     }
 
     @Override
@@ -136,7 +157,7 @@ public void pretrain(List<GazeteerEntry> aData, RecommenderContext aContext)
 
         if (aData != null) {
             for (var entry : aData) {
-                learn(dict, entry.text, entry.label);
+                learn(dict, entry.text, entry.label, true);
             }
 
             aContext.log(LogMessage.info(getRecommender().getName(),
@@ -148,12 +169,17 @@ public void pretrain(List<GazeteerEntry> aData, RecommenderContext aContext)
 
     private <T> Trie<T> createTrie()
     {
-        return new Trie<>(WhitespaceNormalizingSanitizer.factory());
+        return new Trie<>(keySanitizerFactory);
     }
 
     @Override
     public void train(RecommenderContext aContext, List<CAS> aCasses) throws RecommendationException
     {
+        if (excludePatternError != null) {
+            aContext.log(LogMessage.error(getRecommender().getName(),
+                    "Ignoring bad exclude pattern: %s", excludePatternError));
+        }
+
         // Pre-load the gazeteers into the model
         if (gazeteerService != null) {
             for (var gaz : gazeteerService.listGazeteers(recommender)) {
@@ -185,13 +211,13 @@ public void train(RecommenderContext aContext, List<CAS> aCasses) throws Recomme
                     var labels = FSUtil.getFeature(ann, predictedFeature, String[].class);
                     if (labels != null) {
                         for (var label : labels) {
-                            learn(dict, ann.getCoveredText(), label);
+                            learn(dict, ann.getCoveredText(), label, false);
                         }
                     }
                 }
                 else {
-                    learn(dict, ann.getCoveredText(),
-                            ann.getFeatureValueAsString(predictedFeature));
+                    learn(dict, ann.getCoveredText(), ann.getFeatureValueAsString(predictedFeature),
+                            false);
                 }
             }
         }
@@ -356,7 +382,7 @@ public EvaluationResult evaluate(List<CAS> aCasses, DataSplitter aDataSplitter)
         Trie<DictEntry> dict = createTrie();
         for (var sample : trainingSet) {
             for (var span : sample.getSpans()) {
-                learn(dict, span.text(), span.label());
+                learn(dict, span.text(), span.label(), false);
             }
         }
 
@@ -391,12 +417,22 @@ public EvaluationResult evaluate(List<CAS> aCasses, DataSplitter aDataSplitter)
                 SAMPLE_UNIT.getSimpleName(), trainingSetSize, testSetSize, trainRatio, NO_LABEL));
     }
 
-    private void learn(Trie<DictEntry> aDict, String aText, String aLabel)
+    private void learn(Trie<DictEntry> aDict, String aText, String aLabel, boolean aBypassLimits)
     {
         if (isBlank(aText)) {
             return;
         }
 
+        if (!aBypassLimits && traits != null) {
+            if (excludePattern != null && excludePattern.matcher(aText).matches()) {
+                return;
+            }
+
+            if (keySanitizerFactory.create().sanitize(aText).length() < traits.getMinLength()) {
+                return;
+            }
+        }
+
         var label = isBlank(aLabel) ? BLANK_LABEL : aLabel;
 
         var text = aText;
diff --git a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommenderTraits.java b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommenderTraits.java
index b5ddca27da7..8694915c8f6 100644
--- a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommenderTraits.java
+++ b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/StringMatchingRecommenderTraits.java
@@ -29,10 +29,16 @@
 public class StringMatchingRecommenderTraits
     implements Serializable
 {
-    private static final long serialVersionUID = -7433406243352691789L;
+    private static final long serialVersionUID = -7329491581513178640L;
 
     private boolean ignoreCase;
 
+    private String excludePattern;
+
+    private int minLength = 3;
+
+    // private int maxLength = 255;
+
     public boolean isIgnoreCase()
     {
         return ignoreCase;
@@ -42,4 +48,35 @@ public void setIgnoreCase(boolean aIgnoreCase)
     {
         ignoreCase = aIgnoreCase;
     }
+
+    public int getMinLength()
+    {
+        return minLength;
+    }
+
+    public void setMinLength(int aMinLength)
+    {
+        minLength = aMinLength;
+    }
+
+    public String getExcludePattern()
+    {
+        return excludePattern;
+    }
+
+    public void setExcludePattern(String aExcludePattern)
+    {
+        excludePattern = aExcludePattern;
+    }
+
+    // public int getMaxLength()
+    // {
+    // return maxLength;
+    // }
+    //
+    // public void setMaxLength(int aMaxLength)
+    // {
+    // maxLength = aMaxLength;
+    // }
+
 }
diff --git a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.html b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.html
index e943b960989..f689fb93730 100644
--- a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.html
+++ b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.html
@@ -21,7 +21,7 @@
     <form wicket:id="form">
       <div class="row form-row" wicket:enclosure="ignoreCase">
         <div class="offset-sm-3 col-sm-9">
-          <div class="form-check">
+          <div class="form-check form-switch">
             <input wicket:id="ignoreCase" class="form-check-input" type="checkbox"/>
             <label wicket:for="ignoreCase" class="form-check-label">
               <wicket:label key="ignoreCase"/>
@@ -29,6 +29,31 @@
           </div>
         </div>
       </div>
+      <div class="row form-row" wicket:enclosure="excludePattern">
+        <label wicket:for="excludePattern" class="col-sm-3 col-form-label">
+          <wicket:label key="excludePattern"/>
+        </label>
+        <div class="col-sm-9">
+          <div class="input-group">
+            <input wicket:id="excludePattern" class="form-control"/>
+            <span class="input-group-text">(.*)</span>
+          </div>
+          <div class="form-text">
+            Regular expression that controls what can be added to the dictionary.
+          </div>
+        </div>
+      </div>
+      <div class="row form-row" wicket:enclosure="minLength">
+        <label wicket:for="minLength" class="col-sm-3 col-form-label">
+          <wicket:label key="minLength"/>
+        </label>
+        <div class="col-sm-9">
+          <input wicket:id="minLength" type="number" class="form-control"/>
+          <div class="form-text">
+            Minimum length for dictionary entries. Shorter entries will not be added.
+          </div>
+        </div>
+      </div>
     </form>
     <wicket:remove>
       <!-- 
diff --git a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.java b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.java
index 4a90ce73941..84cfead6a6e 100644
--- a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.java
+++ b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.java
@@ -37,6 +37,8 @@
 import org.apache.wicket.markup.html.basic.Label;
 import org.apache.wicket.markup.html.form.CheckBox;
 import org.apache.wicket.markup.html.form.Form;
+import org.apache.wicket.markup.html.form.NumberTextField;
+import org.apache.wicket.markup.html.form.TextField;
 import org.apache.wicket.markup.html.link.DownloadLink;
 import org.apache.wicket.markup.html.list.ListItem;
 import org.apache.wicket.markup.html.list.ListView;
@@ -51,7 +53,7 @@
 
 import de.agilecoders.wicket.extensions.markup.html.bootstrap.form.fileinput.FileInputConfig;
 import de.tudarmstadt.ukp.clarin.webanno.model.AnnotationFeature;
-import de.tudarmstadt.ukp.inception.bootstrap.BootstrapFileInput;
+import de.tudarmstadt.ukp.inception.bootstrap.BootstrapFileInputField;
 import de.tudarmstadt.ukp.inception.recommendation.api.model.Recommender;
 import de.tudarmstadt.ukp.inception.recommendation.api.recommender.DefaultTrainableRecommenderTraitsEditor;
 import de.tudarmstadt.ukp.inception.recommendation.api.recommender.RecommendationEngineFactory;
@@ -76,7 +78,7 @@ public class StringMatchingRecommenderTraitsEditor
     private final StringMatchingRecommenderTraits traits;
 
     private GazeteerList gazeteers;
-    private BootstrapFileInput uploadField;
+    private BootstrapFileInputField uploadField;
 
     public StringMatchingRecommenderTraitsEditor(String aId, IModel<Recommender> aRecommender)
     {
@@ -87,7 +89,7 @@ public StringMatchingRecommenderTraitsEditor(String aId, IModel<Recommender> aRe
         var form = new Form<StringMatchingRecommenderTraits>(MID_FORM,
                 CompoundPropertyModel.of(Model.of(traits)))
         {
-            private static final long serialVersionUID = -3109239605742291123L;
+            private static final long serialVersionUID = -1L;
 
             @Override
             protected void onSubmit()
@@ -96,6 +98,7 @@ protected void onSubmit()
                 toolFactory.writeTraits(aRecommender.getObject(), traits);
             }
         };
+        add(form);
 
         var ignoreCase = new CheckBox("ignoreCase");
         ignoreCase.setOutputMarkupId(true);
@@ -103,7 +106,13 @@ protected void onSubmit()
                 .map(Recommender::getFeature) //
                 .map(this::isStringBasedFeature)));
         form.add(ignoreCase);
-        add(form);
+
+        form.add(new NumberTextField<>("minLength", Integer.class) //
+                .setMinimum(1) //
+                .setMaximum(500) //
+                .setStep(1));
+
+        form.add(new TextField<>("excludePattern", String.class));
 
         gazeteers = new GazeteerList("gazeteers", LoadableDetachableModel.of(this::listGazeteers));
         gazeteers.add(visibleWhen(getModel().map(Recommender::getId).isPresent()));
@@ -114,9 +123,9 @@ protected void onSubmit()
         config.allowedFileExtensions(asList("txt"));
         config.showPreview(false);
         config.showUpload(true);
-        uploadField = new BootstrapFileInput("upload", new ListModel<>(), config)
+        uploadField = new BootstrapFileInputField("upload", new ListModel<>(), config)
         {
-            private static final long serialVersionUID = -7072183979425490246L;
+            private static final long serialVersionUID = -1L;
 
             @Override
             protected void onSubmit(AjaxRequestTarget aTarget)
@@ -195,7 +204,7 @@ private List<Gazeteer> listGazeteers()
     public class GazeteerList
         extends WebMarkupContainer
     {
-        private static final long serialVersionUID = -2049981253344229438L;
+        private static final long serialVersionUID = -1L;
 
         private ListView<Gazeteer> gazeteerList;
 
@@ -207,7 +216,7 @@ public GazeteerList(String aId, IModel<? extends List<Gazeteer>> aChoices)
 
             gazeteerList = new ListView<Gazeteer>("gazeteer", aChoices)
             {
-                private static final long serialVersionUID = 2827701590781214260L;
+                private static final long serialVersionUID = -1L;
 
                 @Override
                 protected void populateItem(ListItem<Gazeteer> aItem)
diff --git a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.properties b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.properties
index f25aac3d2e8..e54f08acf37 100644
--- a/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.properties
+++ b/inception/inception-imls-stringmatch/src/main/java/de/tudarmstadt/ukp/inception/recommendation/imls/stringmatch/span/settings/StringMatchingRecommenderTraitsEditor.properties
@@ -15,3 +15,5 @@
 # limitations under the License.
 gazeteers=Gazeteers
 ignoreCase=Case insensitive
+excludePattern=Exclude pattern
+minLength=Minimum length