diff --git a/src/main/java/org/aksw/gerbil/dataset/impl/wsdm/WSDMDataset.java b/src/main/java/org/aksw/gerbil/dataset/impl/wsdm/WSDMDataset.java
index 60def5a4b..a23ca3fb8 100644
--- a/src/main/java/org/aksw/gerbil/dataset/impl/wsdm/WSDMDataset.java
+++ b/src/main/java/org/aksw/gerbil/dataset/impl/wsdm/WSDMDataset.java
@@ -19,6 +19,7 @@
 import org.aksw.gerbil.transfer.nif.Marking;
 import org.aksw.gerbil.transfer.nif.data.Annotation;
 import org.aksw.gerbil.transfer.nif.data.DocumentImpl;
+import org.aksw.gerbil.transfer.nif.data.NamedEntity;
 import org.aksw.gerbil.utils.WikipediaHelper;
 import org.json.JSONObject;
 import org.slf4j.Logger;
@@ -62,7 +63,7 @@ private List<Document> loadDocuments(File annotations, File tweets)
 		String documentUriPrefix = "http://" + getName() + "/";
 		//its json per line 
 		try (BufferedReader bReader = new BufferedReader(new InputStreamReader(
-				new FileInputStream(tweetsFile), Charset.forName("UTF-8")))) {
+				new FileInputStream(tweets), Charset.forName("UTF-8")))) {
 			String line;
 			List<Marking> markings;
 			while ((line = bReader.readLine()) != null) {
@@ -90,7 +91,6 @@ protected static List<Marking> findMarkings(Set<String> lines, String text) {
 
 			String uri = WikipediaHelper.getWikipediaUri(WIKIPEDIA_DOMAIN , annotation[2]);
 			markings.add(new Annotation(uri));
-
 		}
 
 		return markings;
diff --git a/src/main/java/org/aksw/gerbil/web/config/AnnotatorsConfig.java b/src/main/java/org/aksw/gerbil/web/config/AnnotatorsConfig.java
index cbaacbdb9..253d81e0a 100644
--- a/src/main/java/org/aksw/gerbil/web/config/AnnotatorsConfig.java
+++ b/src/main/java/org/aksw/gerbil/web/config/AnnotatorsConfig.java
@@ -29,6 +29,7 @@
 import org.aksw.gerbil.annotator.SingletonAnnotatorConfigImpl;
 import org.aksw.gerbil.config.GerbilConfiguration;
 import org.aksw.gerbil.datatypes.ExperimentType;
+import org.aksw.gerbil.web.config.check.Checker;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.context.annotation.Bean;
@@ -46,6 +47,9 @@ public class AnnotatorsConfig {
     public static final String ANNOTATOR_EXPERIMENT_TYPE_SUFFIX = "experimentType";
     public static final String ANNOTATOR_NAME_SUFFIX = "name";
     public static final String ANNOTATOR_SINGLETON_FLAG_SUFFIX = "singleton";
+    
+    public static final String ANNOTATOR_CHECK_CLASS_SUFFIX = "check.class";
+    public static final String ANNOTATOR_CHECK_ARGS_SUFFIX = "check.args";
 
     public static void main(String[] args) {
         annotators();
@@ -95,7 +99,7 @@ private static AnnotatorConfiguration getConfiguration(String annotatorKey)
         org.apache.commons.configuration.Configuration config = GerbilConfiguration.getInstance();
         StringBuilder keyBuilder = new StringBuilder();
         String key;
-
+        
         key = buildKey(keyBuilder, annotatorKey, ANNOTATOR_NAME_SUFFIX);
         if (!config.containsKey(key)) {
             LOGGER.error("Couldn't get a name for the \"" + annotatorKey + "\" annotator.");
@@ -144,6 +148,36 @@ private static AnnotatorConfiguration getConfiguration(String annotatorKey)
             constructorArgClasses[i] = String.class;
         }
         Constructor<? extends Annotator> constructor = annotatorClass.getConstructor(constructorArgClasses);
+        
+     // If a checker class has been defined
+        key = buildKey(keyBuilder, annotatorKey, ANNOTATOR_CHECK_CLASS_SUFFIX);
+        if (config.containsKey(key)) {
+            String checkerClassName = config.getString(key);
+            // If checker arguments have been defined
+            key = buildKey(keyBuilder, annotatorKey, ANNOTATOR_CHECK_ARGS_SUFFIX);
+            String checkerArgStrings[];
+            if (config.containsKey(key)) {
+                checkerArgStrings = config.getStringArray(key);
+            } else {
+                checkerArgStrings = new String[0];
+            }
+            Object checkerArgs[] = new Object[checkerArgStrings.length];
+            for (int i = 0; i < checkerArgs.length; ++i) {
+                checkerArgs[i] = checkerArgStrings[i];
+            }
+            try {
+                @SuppressWarnings("unchecked")
+                Class<? extends Checker> checkerClass = (Class<? extends Checker>) AnnotatorsConfig.class.getClassLoader()
+                        .loadClass(checkerClassName);
+                Checker checker = checkerClass.newInstance();
+                if (!checker.check(checkerArgs)) {
+                    LOGGER.info("Check for annotator \"{}\" failed. It won't be available.", name);
+                    return null;
+                }
+            } catch (Exception e) {
+                LOGGER.error("Error while trying to run check for annotator \"" + name + "\". Returning null.", e);
+            }
+        }
 
         if (isSingleton) {
             return new SingletonAnnotatorConfigImpl(name, cacheable, constructor, constructorArgs, type);
diff --git a/src/main/java/org/aksw/gerbil/web/config/check/AnnotatorChecker.java b/src/main/java/org/aksw/gerbil/web/config/check/AnnotatorChecker.java
new file mode 100644
index 000000000..007f5aff2
--- /dev/null
+++ b/src/main/java/org/aksw/gerbil/web/config/check/AnnotatorChecker.java
@@ -0,0 +1,30 @@
+package org.aksw.gerbil.web.config.check;
+
+import org.aksw.gerbil.config.GerbilConfiguration;
+import org.apache.commons.configuration.Configuration;
+
+/**
+ * A {@link Checker} that checks whether the given object(s) (interpreted as
+ * String) are defined properties.
+ * 
+ *
+ */
+public class AnnotatorChecker implements Checker{
+	private static Configuration config= GerbilConfiguration.getInstance();
+
+	@Override
+	public boolean check(Object... objects) {
+		
+		for(Object it: objects){
+			Object prop=config.getProperty(it.toString());
+			if(prop==null){
+				return false;
+			}
+			
+		}
+		
+		
+		return true;
+	}
+
+}
diff --git a/src/main/properties/annotators.properties b/src/main/properties/annotators.properties
index 679220673..de6ccac9b 100644
--- a/src/main/properties/annotators.properties
+++ b/src/main/properties/annotators.properties
@@ -73,6 +73,8 @@ org.aksw.gerbil.annotators.definition.EcEU.name=Entityclassifier.eu NER
 org.aksw.gerbil.annotators.definition.EcEU.experimentType=A2KB
 org.aksw.gerbil.annotators.definition.EcEU.cacheable=true
 org.aksw.gerbil.annotators.definition.EcEU.class=org.aksw.gerbil.annotator.impl.nif.NIFBasedAnnotatorWebservice
+org.aksw.gerbil.annotators.definition.EcEU.check.class=org.aksw.gerbil.web.config.check.AnnotatorChecker
+org.aksw.gerbil.annotators.definition.EcEU.check.args=org.aksw.gerbil.annotators.EntityclassifierEUConfig.apiKey
 org.aksw.gerbil.annotators.definition.EcEU.constructorArgs=${org.aksw.gerbil.annotators.EntityclassifierEUConfig.url}${org.aksw.gerbil.annotators.EntityclassifierEUConfig.apiKey}
 
 ### FRED
@@ -130,14 +132,21 @@ org.aksw.gerbil.annotators.definition.kea.experimentType=A2KB
 org.aksw.gerbil.annotators.definition.kea.cacheable=true
 #org.aksw.gerbil.annotators.definition.kea.singleton=true
 org.aksw.gerbil.annotators.definition.kea.class=org.aksw.gerbil.annotator.impl.nif.NIFBasedAnnotatorWebservice
+org.aksw.gerbil.annotators.definition.kea.check.class=org.aksw.gerbil.web.config.check.AnnotatorChecker
+org.aksw.gerbil.annotators.definition.kea.check.args=org.aksw.gerbil.annotators.KeaAnnotatorConfig.user
+org.aksw.gerbil.annotators.definition.kea.check.args=org.aksw.gerbil.annotators.KeaAnnotatorConfig.password
 org.aksw.gerbil.annotators.definition.kea.constructorArgs=http://${org.aksw.gerbil.annotators.KeaAnnotatorConfig.user}:${org.aksw.gerbil.annotators.KeaAnnotatorConfig.password}@${org.aksw.gerbil.annotators.KeaAnnotatorConfig.annotationUrl}
 org.aksw.gerbil.annotators.definition.kea2.name=Kea
 org.aksw.gerbil.annotators.definition.kea2.experimentType=D2KB
 org.aksw.gerbil.annotators.definition.kea2.cacheable=true
 #org.aksw.gerbil.annotators.definition.kea2.singleton=true
 org.aksw.gerbil.annotators.definition.kea2.class=org.aksw.gerbil.annotator.impl.nif.NIFBasedAnnotatorWebservice
+org.aksw.gerbil.annotators.definition.kea2.check.class=org.aksw.gerbil.web.config.check.AnnotatorChecker
+org.aksw.gerbil.annotators.definition.kea2.check.args=org.aksw.gerbil.annotators.KeaAnnotatorConfig.user
+org.aksw.gerbil.annotators.definition.kea2.check.args=org.aksw.gerbil.annotators.KeaAnnotatorConfig.password
 org.aksw.gerbil.annotators.definition.kea2.constructorArgs=http://${org.aksw.gerbil.annotators.KeaAnnotatorConfig.user}:${org.aksw.gerbil.annotators.KeaAnnotatorConfig.password}@${org.aksw.gerbil.annotators.KeaAnnotatorConfig.disambiguationUrl}
 
+
 ### NERD-ML
 #NERD endpoint
 org.aksw.gerbil.annotators.NERD.host=http://nerd.eurecom.fr/api/
@@ -147,6 +156,8 @@ org.aksw.gerbil.annotators.definition.NERD.name=NERD-ML
 org.aksw.gerbil.annotators.definition.NERD.experimentType=A2KB
 org.aksw.gerbil.annotators.definition.NERD.cacheable=true
 org.aksw.gerbil.annotators.definition.NERD.class=org.aksw.gerbil.annotator.impl.nerd.NERDAnnotator
+org.aksw.gerbil.annotators.definition.NERD.check.class=org.aksw.gerbil.web.config.check.AnnotatorChecker
+org.aksw.gerbil.annotators.definition.NERD.check.args=org.aksw.gerbil.annotators.nerd.Key
 org.aksw.gerbil.annotators.definition.NERD.constructorArgs=${org.aksw.gerbil.annotators.NERD.host}
 
 ### NERFGUN
@@ -170,6 +181,9 @@ org.aksw.gerbil.annotators.TagmeAnnotator.annotateUrl=https://tagme.d4science.or
 org.aksw.gerbil.annotators.TagmeAnnotator.spotUrl=https://tagme.d4science.org/tagme/spot
 #Use this property to set the TagMe key (moved this to the gerbil_keys.properties file)
 #org.aksw.gerbil.annotators.TagMe.key
+org.aksw.gerbil.annotators.definition.TagMe.check.class=org.aksw.gerbil.web.config.check.AnnotatorChecker
+org.aksw.gerbil.annotators.definition.TagMe.check.args=org.aksw.gerbil.annotators.TagMe.key
+
 org.aksw.gerbil.annotators.definition.TagMe.name=TagMe 2
 org.aksw.gerbil.annotators.definition.TagMe.experimentType=A2KB
 org.aksw.gerbil.annotators.definition.TagMe.cacheable=true