diff --git a/Changes b/Changes
index bac3b68..ed0ba02 100644
--- a/Changes
+++ b/Changes
@@ -17,7 +17,8 @@
 	  renamed /analysis to /model,
 	  renamed shrink() to focus(),
 	  removed KorapPrimaryData,
-          fixed a lot of wrong tests for WithinSpans (diewald)
+          fixed a lot of wrong tests for WithinSpans,
+	  renamed KorapFilter to /collection/CollectionBuilder (diewald)
         - [feature] Improved deserialization of SpanSubSpanQueries
           (margaretha)
 	- [feature] Introducing the potential need for resorting queries
diff --git a/src/main/java/de/ids_mannheim/korap/KorapCollection.java b/src/main/java/de/ids_mannheim/korap/KorapCollection.java
index 6e4ad8e..232b5bb 100644
--- a/src/main/java/de/ids_mannheim/korap/KorapCollection.java
+++ b/src/main/java/de/ids_mannheim/korap/KorapCollection.java
@@ -8,6 +8,7 @@
 import de.ids_mannheim.korap.util.QueryException;
 import de.ids_mannheim.korap.collection.BooleanFilter;
 import de.ids_mannheim.korap.collection.FilterOperation;
+import de.ids_mannheim.korap.collection.CollectionBuilder;
 import de.ids_mannheim.korap.response.Notifications;
 
 import org.apache.lucene.search.spans.SpanQuery;
@@ -26,28 +27,32 @@
 import org.slf4j.LoggerFactory;
 
 /**
- * That's a pretty ugly API to
- * create virtual collections.
- * It works - so I got that going for
- * me, which is nice.
+ * Create a Virtual Collection of documents by means of a KoralQuery
+ * or by applying manual filters and extensions on Lucene fields.
+ *
+ * <blockquote><pre>
+ *   KorapCollection kc = new KorapCollection(json);
+ *   kc.filterUIDS("a1", "a2", "a3");
+ * </pre></blockquote>
+ *
+ * <strong>Warning</strong>: This API is deprecated and will
+ * be replaced in future versions. It supports legacy versions of
+ * KoralQuery.
  *
  * @author diewald
  */
-
-
-// TODO: Make a cache for the bits!!! DELETE IT IN CASE OF AN EXTENSION OR A FILTER!
-// TODO: Maybe use randomaccessfilterstrategy
-// TODO: Maybe a constantScoreQuery can make things faster?
-
-// THIS MAY CHANGE for stuff like combining virtual collections
-// See http://mail-archives.apache.org/mod_mbox/lucene-java-user/
-//     200805.mbox/%3C17080852.post@talk.nabble.com%3E
-
+/*
+ * TODO: Make a cache for the bits
+ *       Delete it in case of an extension or a filter
+ * TODO: Maybe use randomaccessfilterstrategy
+ * TODO: Maybe a constantScoreQuery can make things faster?
+ * See http://mail-archives.apache.org/mod_mbox/lucene-java-user/
+ *     200805.mbox/%3C17080852.post@talk.nabble.com%3E
+ */
 public class KorapCollection extends Notifications {
     private KorapIndex index;
     private KorapDate created;
     private String id;
-    //    private String error;
     private ArrayList<FilterOperation> filter;
     private int filterCount = 0;
     
@@ -62,10 +67,13 @@
         this.filter = new ArrayList<FilterOperation>(5);
     };
 
+
     /**
-     * Construct a new KorapCollection by passing a JSON query.
-     * This supports collections with key "collection" and
+     * Construct a new KorapCollection by passing a KoralQuery.
+     * This supports collections with the key "collection" and
      * legacy collections with the key "collections".
+     *
+     * @param jsonString The virtual collection as a KoralQuery.
      */
     public KorapCollection (String jsonString) {
         ObjectMapper mapper = new ObjectMapper();
@@ -73,7 +81,8 @@
 
         try {
             JsonNode json = mapper.readTree(jsonString);
-
+            
+            // Deserialize from recent collections
             if (json.has("collection")) {
                 this.fromJSON(json.get("collection"));
             }
@@ -90,8 +99,9 @@
                 };
             };
         }
+        // Some exceptions ...
         catch (QueryException qe) {
-            this.addError(qe.getErrorCode(),qe.getMessage());
+            this.addError(qe.getErrorCode(), qe.getMessage());
         }
         catch (IOException e) {
             this.addError(
@@ -104,11 +114,20 @@
     };
 
 
+    /**
+     * Construct a new KorapCollection.
+     */
     public KorapCollection () {
         this.filter = new ArrayList<FilterOperation>(5);
     };
 
 
+    /**
+     * Import the "collection" part of a KoralQuery.
+     *
+     * @param jsonString The "collection" part of a KoralQuery.
+     * @throws QueryException
+     */
     public void fromJSON (String jsonString) throws QueryException {
         ObjectMapper mapper = new ObjectMapper();
         try {
@@ -120,14 +139,26 @@
     };
 
 
+    /**
+     * Import the "collection" part of a KoralQuery.
+     *
+     * @param json The "collection" part of a KoralQuery
+     *        as a {@link JsonNode} object.
+     * @throws QueryException
+     */
     public void fromJSON (JsonNode json) throws QueryException {
-        this.filter(new KorapFilter(json));
+        this.filter(new CollectionBuilder(json));
     };
 
 
     /**
-     * Legacy API for collection filters.
+     * Import the "collections" part of a KoralQuery.
+     * This method is deprecated and will vanish in future versions.
+     *
+     * @param jsonString The "collections" part of a KoralQuery.
+     * @throws QueryException
      */
+    @Deprecated
     public void fromJSONLegacy (String jsonString) throws QueryException {
         ObjectMapper mapper = new ObjectMapper();
         try {
@@ -140,7 +171,12 @@
 
 
     /**
-     * Legacy API for collection filters.
+     * Import the "collections" part of a KoralQuery.
+     * This method is deprecated and will vanish in future versions.
+     *
+     * @param json The "collections" part of a KoralQuery
+     *        as a {@link JsonNode} object.
+     * @throws QueryException
      */
     public void fromJSONLegacy (JsonNode json) throws QueryException {
         if (!json.has("@type"))
@@ -151,14 +187,17 @@
 
         String type = json.get("@type").asText();
 
-        KorapFilter kf = new KorapFilter();
+        CollectionBuilder kf = new CollectionBuilder();
         kf.setBooleanFilter(kf.fromJSONLegacy(json.get("@value"), "tokens"));
+
+        // Filter the collection
         if (type.equals("korap:meta-filter")) {
             if (DEBUG)
                 log.trace("Add Filter LEGACY");
             this.filter(kf);
         }
-
+        
+        // Extend the collection
         else if (type.equals("korap:meta-extend")) {
             if (DEBUG)
                 log.trace("Add Extend LEGACY");
@@ -166,15 +205,27 @@
         };
     };
 
-    public int getCount() {
-        return this.filterCount;
+
+    /**
+     * Set the {@link KorapIndex} the virtual collection refers to.
+     *
+     * @param index The {@link KorapIndex} the virtual collection refers to.
+     */
+    public void setIndex (KorapIndex index) {
+        this.index = index;
     };
 
-    public void setIndex (KorapIndex ki) {
-        this.index = ki;
-    };
 
-    // The checks asre not necessary
+    /**
+     * Add a filter by means of a {@link BooleanFilter}.
+     *
+     * <strong>Warning</strong>: Filters are part of the collections
+     * legacy API and may vanish without warning.
+     *
+     * @param filter The filter to add to the collection.
+     * @return The {@link KorapCollection} object for chaining.
+     */
+    // TODO: The checks may not be necessary
     public KorapCollection filter (BooleanFilter filter) {
         if (DEBUG)
             log.trace("Added filter: {}", filter.toString());
@@ -199,7 +250,68 @@
         return this;
     };
 
-    // Filter based on UIDs
+
+    /**
+     * Add a filter by means of a {@link CollectionBuilder} object.
+     *
+     * <strong>Warning</strong>: Filters are part of the collections
+     * legacy API and may vanish without warning.
+     *
+     * @param filter The filter to add to the collection.
+     * @return The {@link KorapCollection} object for chaining.
+     */
+    public KorapCollection filter (CollectionBuilder filter) {
+        return this.filter(filter.getBooleanFilter());
+    };
+
+
+    /**
+     * Add an extension by means of a {@link BooleanFilter}.
+     *
+     * <strong>Warning</strong>: Extensions are part of the collections
+     * legacy API and may vanish without warning.
+     *
+     * @param extension The extension to add to the collection.
+     * @return The {@link KorapCollection} object for chaining.
+     */
+    public KorapCollection extend (BooleanFilter extension) {
+        if (DEBUG)
+            log.trace("Added extension: {}", extension.toString());
+
+        this.filter.add(
+            new FilterOperation(
+                (Filter) new QueryWrapperFilter(extension.toQuery()),
+                true
+            )
+        );
+        this.filterCount++;
+        return this;
+    };
+
+
+    /**
+     * Add an extension by means of a {@link CollectionBuilder} object.
+     *
+     * <strong>Warning</strong>: Extensions are part of the collections
+     * legacy API and may vanish without warning.
+     *
+     * @param extension The extension to add to the collection.
+     * @return The {@link KorapCollection} object for chaining.
+     */
+    public KorapCollection extend (CollectionBuilder extension) {
+        return this.extend(extension.getBooleanFilter());
+    };
+
+
+    /**
+     * Add a filter based on a list of unique document identifiers.
+     * UIDs may be indexed in the field "UID".
+     *
+     * This filter is not part of the legacy API!
+     *
+     * @param uids The list of unique document identifier.
+     * @return The {@link KorapCollection} object for chaining.
+     */
     public KorapCollection filterUIDs (String ... uids) {
         BooleanFilter filter = new BooleanFilter();
         filter.or("UID", uids);
@@ -209,38 +321,55 @@
     };
 
 
-    public KorapCollection filter (KorapFilter filter) {
-        return this.filter(filter.getBooleanFilter());
-    };
-
-
-    public KorapCollection extend (BooleanFilter filter) {
-        if (DEBUG)
-            log.trace("Added extension: {}", filter.toString());
-        this.filter.add(
-            new FilterOperation(
-                (Filter) new QueryWrapperFilter(filter.toQuery()),
-                true
-            )
-        );
-        this.filterCount++;
-        return this;
-    };
-
-    public KorapCollection extend (KorapFilter filter) {
-        return this.extend(filter.getBooleanFilter());
-    };
-
-    
-    public ArrayList<FilterOperation> getFilters () {
+    /**
+     * Get the list of filters constructing the collection.
+     *
+     * <strong>Warning</strong>: This is part of the collections
+     * legacy API and may vanish without warning.
+     *
+     * @return The list of filters.
+     */
+    public List<FilterOperation> getFilters () {
         return this.filter;
     };
 
-    public FilterOperation getFilter (int i) {
-        return this.filter.get(i);
+
+    /**
+     * Get a certain {@link FilterOperation} from the list of filters
+     * constructing the collection by its numerical index.
+     *
+     * <strong>Warning</strong>: This is part of the collections
+     * legacy API and may vanish without warning.
+     *
+     * @param index The index position of the requested {@link FilterOperation}.
+     * @return The {@link FilterOperation} at the certain list position.
+     */
+    public FilterOperation getFilter (int index) {
+        return this.filter.get(index);
     };
 
 
+    /**
+     * Get the number of filter operations constructing this collection.
+     *
+     * <strong>Warning</strong>: This is part of the collections
+     * legacy API and may vanish without warning.
+     *
+     * @return The number of filter operations constructing this collection.
+     */
+    public int getCount() {
+        return this.filterCount;
+    };
+
+
+    /**
+     * Generate a string representatio of the virtual collection.
+     *
+     * <strong>Warning</strong>: This currently does not generate a valid
+     * KoralQuery string, so this may change in a future version.
+     *
+     * @return A string representation of the virtual collection.
+     */
     public String toString () {
         StringBuilder sb = new StringBuilder();
         for (FilterOperation fo : this.filter) {
@@ -249,9 +378,19 @@
         return sb.toString();
     };
 
+
     /**
-     * Search in the virtual collection. This is just used for
-     * testing purposes and not recommended for serious usage. 
+     * Search in the virtual collection.
+     * This is mostly used for testing purposes
+     * and <strong>is not recommended</strong>
+     * as a common search API.
+     *
+     * Please use {@link KorapQuery#run} instead.
+     *
+     * @param query a {@link SpanQuery} to apply on the
+     *        virtual collection.
+     * @return A {@link KorapResult} object representing the search's
+     *         result.
      */
     public KorapResult search (SpanQuery query) {
         return this.index.search(
@@ -264,37 +403,47 @@
         );
     };
 
+
+    /**
+     * Create a bit vector representing the live documents of the
+     * virtual collection to be used in searches.
+     *
+     * @param The {@link AtomicReaderContext} to search in.
+     * @return A bit vector representing the live documents of the
+     *         virtual collection.
+     * @throws IOException
+     */
     public FixedBitSet bits (AtomicReaderContext atomic) throws IOException  {
-        /*
-          Use Bits.MatchAllBits(int len)
-        */
+        // TODO: Probably use Bits.MatchAllBits(int len)
         boolean noDoc = true;
         FixedBitSet bitset;
-
+        
+        // There are filters set
         if (this.filterCount > 0) {
             bitset = new FixedBitSet(atomic.reader().maxDoc());
 
-            ArrayList<FilterOperation> filters = (ArrayList<FilterOperation>) this.filter.clone();
+            ArrayList<FilterOperation> filters =
+                (ArrayList<FilterOperation>) this.filter.clone();
 
             FilterOperation kcInit = filters.remove(0);
             if (DEBUG)
                 log.trace("FILTER: {}", kcInit);
-
+            
             // Init vector
             DocIdSet docids = kcInit.filter.getDocIdSet(atomic, null);
 
             DocIdSetIterator filterIter = docids.iterator();
-
+            
+            // The filter has an effect
             if (filterIter != null) {
-                if (DEBUG)
-                    log.trace("InitFilter has effect");
+                if (DEBUG) log.trace("InitFilter has effect");
                 bitset.or(filterIter);
                 noDoc = false;
             };
-
+            
+            // Apply all filters sequentially
             for (FilterOperation kc : filters) {
-                if (DEBUG)
-                    log.trace("FILTER: {}", kc);
+                if (DEBUG) log.trace("FILTER: {}", kc);
 
                 // TODO: BUG???
                 docids = kc.filter.getDocIdSet(atomic, kc.isExtension() ? null : bitset);
@@ -310,22 +459,16 @@
                     };
                     continue;
                 };
-                if (kc.isExtension()) {
-                    // System.err.println("Term found!");
-                    // System.err.println("Old Card:" + bitset.cardinality());
+                if (kc.isExtension())
                     bitset.or(filterIter);
-                    // System.err.println("New Card:" + bitset.cardinality());
-                }
-                else {
+                else
                     bitset.and(filterIter);
-                };
             };
 
             if (!noDoc) {
                 FixedBitSet livedocs = (FixedBitSet) atomic.reader().getLiveDocs();
-                if (livedocs != null) {
+                if (livedocs != null)
                     bitset.and(livedocs);
-                };
             };
         }
         else {
@@ -335,13 +478,39 @@
         return bitset;
     };
 
-    public long numberOf (String foundry, String type) throws IOException {
+
+    /**
+     * Search for the number of occurrences of different types,
+     * e.g. <i>documents</i>, <i>sentences</i> etc. in the virtual
+     * collection.
+     *
+     * @param field The field containing the textual data and the
+     *        annotations as a string.
+     * @param type The type of meta information,
+     *        e.g. <i>documents</i> or <i>sentences</i> as a string.
+     * @return The number of the occurrences.
+     * @throws IOException
+     * @see KorapIndex#numberOf
+     */
+    public long numberOf (String field, String type) throws IOException {
         if (this.index == null)
             return (long) -1;
 
-        return this.index.numberOf(this, foundry, type);
+        return this.index.numberOf(this, field, type);
     };
 
+
+    /**
+     * Search for the number of occurrences of different types,
+     * e.g. <i>documents</i>, <i>sentences</i> etc. in the virtual
+     * collection, in the <i>base</i> foundry.
+     *
+     * @param type The type of meta information,
+     *        e.g. <i>documents</i> or <i>sentences</i> as a string.
+     * @return The number of the occurrences.
+     * @throws IOException
+     * @see KorapIndex#numberOf
+     */
     public long numberOf (String type) throws IOException {
         if (this.index == null)
             return (long) -1;
@@ -349,9 +518,9 @@
         return this.index.numberOf(this, "tokens", type);
     };
 
-    // This is only for testing purposes!
+
     @Deprecated
-    public HashMap getTermRelation(String field) throws Exception {
+    public HashMap getTermRelation (String field) throws Exception {
         if (this.index == null) {
             HashMap<String,Long> map = new HashMap<>(1);
             map.put("-docs", (long) 0);
@@ -361,8 +530,9 @@
         return this.index.getTermRelation(this, field);
     };
 
+
     @Deprecated
-    public String getTermRelationJSON(String field) throws IOException {
+    public String getTermRelationJSON (String field) throws IOException {
         ObjectMapper mapper = new ObjectMapper();
         StringWriter sw = new StringWriter();
         sw.append("{\"field\":");
diff --git a/src/main/java/de/ids_mannheim/korap/KorapIndex.java b/src/main/java/de/ids_mannheim/korap/KorapIndex.java
index 17ffb03..d64fd7f 100644
--- a/src/main/java/de/ids_mannheim/korap/KorapIndex.java
+++ b/src/main/java/de/ids_mannheim/korap/KorapIndex.java
@@ -36,6 +36,24 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+/**
+ * KorapIndex implements a simple API for searching in and writing to a
+ * Lucene index and requesting several information about the index' nature.
+ * <br />
+ *
+ * <blockquote><pre>
+ *   KorapIndex ki = new KorapIndex(
+ *       new MMapDirectory(new File("/myindex"))
+ *   );
+ * </pre></blockquote>
+ *
+ * Properties can be stored in a properies file called 'index.properties'.
+ * Relevant properties are <code>lucene.version</code> and
+ * <code>lucene.name</code>.
+ *
+ * @author diewald
+ */
+
 /*
   TODO: Add word count as a meta data field!
   TODO: Validate document import!
@@ -61,25 +79,6 @@
   -> search for frequencies of VVFIN/gehen
   -> c:VVFIN:[^:]*?:gehen:past:...
 */
-
-/**
- *
- * KorapIndex implements a simple API for searching in and writing to a
- * Lucene index and requesting several information about the index' nature.
- * <br />
- *
- * <pre>
- *   KorapIndex ki = new KorapIndex(
- *       new MMapDirectory(new File("/myindex"))
- *   );
- * </pre>
- *
- * Properties can be stored in a properies file called 'index.properties'.
- * Relevant properties are <code>lucene.version</code> and
- * <code>lucene.name</code>.
- *
- * @author diewald
- */
 public class KorapIndex {
 
     // Todo: Use configuration
@@ -468,6 +467,7 @@
      * @param type The type of meta information,
      *        e.g. <i>documents</i> or <i>sentences</i> as a string.
      * @return The number of the occurrences.
+     * @see KorapCollection#numberOf
      */
     public long numberOf (KorapCollection collection,
                           String field,
@@ -524,7 +524,17 @@
     };
 
 
-
+    /**
+     * Search for the number of occurrences of different types,
+     * e.g. <i>documents</i>, <i>sentences</i> etc.
+     *
+     * @param field The field containing the textual data and the
+     *        annotations as a string.
+     * @param type The type of meta information,
+     *        e.g. <i>documents</i> or <i>sentences</i> as a string.
+     * @return The number of the occurrences.
+     * @see KorapCollection#numberOf
+     */
     public long numberOf (String field, String type) {
         return this.numberOf(new KorapCollection(this), field, type);
     };
@@ -538,6 +548,7 @@
      * @param type The type of meta information,
      *        e.g. <i>documents</i> or <i>sentences</i> as a string.
      * @return The number of the occurrences.
+     * @see KorapCollection#numberOf
      */
     public long numberOf (String type) {
         return this.numberOf("tokens", type);
diff --git a/src/main/java/de/ids_mannheim/korap/collection/BooleanFilter.java b/src/main/java/de/ids_mannheim/korap/collection/BooleanFilter.java
index 1d755dd..2388729 100644
--- a/src/main/java/de/ids_mannheim/korap/collection/BooleanFilter.java
+++ b/src/main/java/de/ids_mannheim/korap/collection/BooleanFilter.java
@@ -12,8 +12,7 @@
 import org.apache.lucene.search.NumericRangeQuery;
 
 import de.ids_mannheim.korap.util.KorapDate;
-import de.ids_mannheim.korap.KorapFilter;
-
+import de.ids_mannheim.korap.KorapCollection;
 import de.ids_mannheim.korap.util.QueryException;
 
 import org.slf4j.Logger;
@@ -35,7 +34,7 @@
     private String type;
 
     // Logger
-    private final static Logger log = LoggerFactory.getLogger(KorapFilter.class);
+    private final static Logger log = LoggerFactory.getLogger(KorapCollection.class);
 
     // This advices the java compiler to ignore all loggings
     public static final boolean DEBUG = false;
diff --git a/src/main/java/de/ids_mannheim/korap/KorapFilter.java b/src/main/java/de/ids_mannheim/korap/collection/CollectionBuilder.java
similarity index 87%
rename from src/main/java/de/ids_mannheim/korap/KorapFilter.java
rename to src/main/java/de/ids_mannheim/korap/collection/CollectionBuilder.java
index b567741..10a6b65 100644
--- a/src/main/java/de/ids_mannheim/korap/KorapFilter.java
+++ b/src/main/java/de/ids_mannheim/korap/collection/CollectionBuilder.java
@@ -1,4 +1,4 @@
-package de.ids_mannheim.korap;
+package de.ids_mannheim.korap.collection;
 
 import de.ids_mannheim.korap.collection.BooleanFilter;
 import de.ids_mannheim.korap.collection.RegexFilter;
@@ -13,37 +13,36 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-
-/*
-  Todo: WildCardFilter!
-  Support: delete boolean etc.
-  Support: supports foundries
-*/
-
 /**
- * @author diewald
- *
- * KorapFilter implements a simple API for creating meta queries
+ * CollectionBuilder implements a simple API for creating queries
  * constituing Virtual Collections.
+ *
+ * @author diewald
  */
-public class KorapFilter {
+/*
+ * Todo: WildCardFilter!
+ * Todo: Support delete boolean etc.
+ * Todo: Supports foundries
+ */
+public class CollectionBuilder {
     private BooleanFilter filter;
 
     // Logger
-    private final static Logger log = LoggerFactory.getLogger(KorapFilter.class);
+    private final static Logger log = LoggerFactory.getLogger(CollectionBuilder.class);
 
     // This advices the java compiler to ignore all loggings
     public static final boolean DEBUG = false;
     
-    public KorapFilter () {
+    public CollectionBuilder () {
         filter = new BooleanFilter();
     };
 
-    public KorapFilter (JsonNode json) throws QueryException {
+    public CollectionBuilder (JsonNode json) throws QueryException {
         filter = this.fromJSON(json, "tokens");
     };
 
-    protected BooleanFilter fromJSON (JsonNode json, String field) throws QueryException {
+
+    public BooleanFilter fromJSON (JsonNode json, String field) throws QueryException {
         BooleanFilter bfilter = new BooleanFilter();
 
         // TODO: THIS UNFORTUNATELY BREAKS TESTS
@@ -70,7 +69,7 @@
 
                 if (!json.has("value"))
                     throw new QueryException(612, "Dates require value fields");
-//-
+
                 String dateStr = json.get("value").asText();
                 if (json.has("match"))
                     match = json.get("match").asText();
@@ -87,18 +86,17 @@
                     bfilter.till(dateStr);
                     break;
                 };
-                /*
-                  No good reason for gt or lt
-                */
+                // No good reason for gt or lt
                 return bfilter;
             }
+
             else if (valtype.equals("type:string")) {
                 if (json.has("match"))
                     match = json.get("match").asText();
 
-                if (match.equals("match:eq")) {
+                if (match.equals("match:eq"))
                     bfilter.and(key, json.get("value").asText());
-                };
+
                 return bfilter;
             };
         }
@@ -106,7 +104,6 @@
         // nested group
         else if (type.equals("korap:docGroup")) {
             if (!json.has("operands") || !json.get("operands").isArray())
-//-
                 throw new QueryException(612, "Groups need operands");
 
             String operation = "operation:and";
@@ -116,30 +113,27 @@
             BooleanFilter group = new BooleanFilter();
 
             for (JsonNode operand : json.get("operands")) {
-                if (operation.equals("operation:and")) {
+                if (operation.equals("operation:and"))
                     group.and(this.fromJSON(operand, field));
-                }
-                else if (operation.equals("operation:or")) {
+
+                else if (operation.equals("operation:or"))
                     group.or(this.fromJSON(operand, field));
-                }
-                else {
+
+                else
                     throw new QueryException(613, "Unknown document group operation");
-                };
             };
             bfilter.and(group);
             return bfilter;
         }
 
         // Unknown type
-        else {
-// -
-            throw new QueryException(613, "Collection query type has to be doc or docGroup");
-        };
-
+        else throw new QueryException(613, "Collection query type has to be doc or docGroup");
+        
         return new BooleanFilter();
     };
-
-	/*
+    
+	
+    /*
       String type = json.get("@type").asText();
       String field = _getField(json);
 
@@ -153,13 +147,11 @@
 	    };
 	};
 	*/
-    //    };
     
-    protected BooleanFilter fromJSONLegacy (JsonNode json, String field)
+    public BooleanFilter fromJSONLegacy (JsonNode json, String field)
         throws QueryException {
         BooleanFilter bfilter = new BooleanFilter();
 
-//-
         if (!json.has("@type"))
             throw new QueryException(612, "JSON-LD group has no @type attribute");
 	
@@ -177,21 +169,16 @@
             return bfilter;
         }
         else if (type.equals("korap:group")) {
-//-
             if (!json.has("relation"))
                 throw new QueryException(612, "Group needs relation");
 
             if (!json.has("operands"))
-//-
                 throw new QueryException(612, "Group needs operand list");
 
-		//return bfilter;
-
             String dateStr, till;
             JsonNode operands = json.get("operands");
 
             if (!operands.isArray())
-//-
                 throw new QueryException(612, "Group needs operand list");
 
             if (DEBUG)
@@ -226,7 +213,6 @@
                 break;
 
             case "and":
-//-
                 if (operands.size() < 1)
                     throw new QueryException(612, "Operation needs at least two operands");
 
@@ -237,7 +223,6 @@
                 break;
 
             case "or":
-//-
                 if (operands.size() < 1)
                     throw new QueryException(612, "Operation needs at least two operands");
 
@@ -247,7 +232,6 @@
                 bfilter.and(group);
                 break;
 
-//-
             default:
                 throw new QueryException(613, "Relation is not supported");
             };
@@ -295,8 +279,6 @@
     };
 
     public BooleanFilter or (String type, String ... terms) {
-        if (DEBUG)
-            log.debug("Got some terms here");
         BooleanFilter bf = new BooleanFilter();
         bf.or(type, terms);
         return bf;
@@ -342,7 +324,7 @@
         return new RegexFilter(regex);
     };
 
-    public BooleanFilter getBooleanFilter()  {
+    public BooleanFilter getBooleanFilter ()  {
         return this.filter;
     };
 
diff --git a/src/test/java/de/ids_mannheim/korap/benchmark/TestBenchmarkSpans.java b/src/test/java/de/ids_mannheim/korap/benchmark/TestBenchmarkSpans.java
index 213d11d..17dea33 100644
--- a/src/test/java/de/ids_mannheim/korap/benchmark/TestBenchmarkSpans.java
+++ b/src/test/java/de/ids_mannheim/korap/benchmark/TestBenchmarkSpans.java
@@ -6,7 +6,6 @@
 import de.ids_mannheim.korap.KorapIndex;
 import de.ids_mannheim.korap.index.FieldDocument;
 import de.ids_mannheim.korap.KorapCollection;
-import de.ids_mannheim.korap.KorapFilter;
 import de.ids_mannheim.korap.KorapSearch;
 import de.ids_mannheim.korap.KorapResult;
 import de.ids_mannheim.korap.KorapQuery;
diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestCollectionBuilder.java b/src/test/java/de/ids_mannheim/korap/collection/TestCollectionBuilder.java
new file mode 100644
index 0000000..18c8e57
--- /dev/null
+++ b/src/test/java/de/ids_mannheim/korap/collection/TestCollectionBuilder.java
@@ -0,0 +1,83 @@
+package de.ids_mannheim.korap.collection;
+
+import java.util.*;
+import java.io.*;
+
+import org.apache.lucene.util.Version;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.Bits;
+
+import static org.junit.Assert.*;
+import org.junit.Test;
+import org.junit.Ignore;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import de.ids_mannheim.korap.collection.CollectionBuilder;
+
+@RunWith(JUnit4.class)
+public class TestCollectionBuilder {
+
+    @Test
+    public void filterExample () throws IOException {
+        CollectionBuilder kf = new CollectionBuilder();
+
+        assertEquals("+textClass:tree", kf.and("textClass","tree").toString());
+        assertEquals("+textClass:tree +textClass:sport", kf.and("textClass","tree").and("textClass","sport").toString());
+        assertEquals("+textClass:tree +textClass:sport textClass:news", kf.and("textClass","tree").and("textClass","sport").or("textClass","news").toString());
+        assertEquals("+textClass:tree +textClass:sport +textClass:news", kf.and("textClass", "tree", "sport", "news").toString());
+
+        assertEquals("corpusID:c-1 corpusID:c-2 corpusID:c-3", kf.or("corpusID", "c-1", "c-2", "c-3").toString());
+    };
+
+
+    @Test
+    public void rangeExample () throws IOException {
+        CollectionBuilder kf = new CollectionBuilder();
+        assertEquals("+pubDate:[20030604 TO 20030899]", kf.between("2003-06-04", "2003-08-99").toString());
+        assertEquals("+pubDate:[0 TO 20030604]", kf.till("2003-06-04").toString());
+        assertEquals("+pubDate:[20030604 TO 99999999]", kf.since("2003-06-04").toString());
+        assertEquals("+pubDate:20030604", kf.date("2003-06-04").toString());
+    };
+
+
+    @Test
+    public void rangeLimited () throws IOException {
+        CollectionBuilder kf = new CollectionBuilder();
+        assertEquals("+pubDate:[20050000 TO 20099999]", kf.between("2005", "2009").toString());
+       	assertEquals("+pubDate:[20051000 TO 20090899]", kf.between("200510", "200908").toString());
+        assertEquals("+pubDate:[20051000 TO 20090899]", kf.between("2005-10", "2009-08").toString());
+        assertEquals("+pubDate:[20051006 TO 20090803]", kf.between("2005-1006", "2009-0803").toString());
+        assertEquals("+pubDate:[20051006 TO 20090803]", kf.between("2005-10-06", "2009-08-03").toString());
+        
+        assertEquals("+pubDate:[0 TO 20059999]", kf.till("2005").toString());
+        assertEquals("+pubDate:[0 TO 20051099]", kf.till("200510").toString());
+        assertEquals("+pubDate:[0 TO 20051099]", kf.till("2005-10").toString());
+        assertEquals("+pubDate:[0 TO 20051006]", kf.till("2005-1006").toString());
+        assertEquals("+pubDate:[0 TO 20051006]", kf.till("2005-10-06").toString());
+
+        assertEquals("+pubDate:[20050000 TO 99999999]", kf.since("2005").toString());
+        assertEquals("+pubDate:[20051000 TO 99999999]", kf.since("200510").toString());
+        assertEquals("+pubDate:[20051000 TO 99999999]", kf.since("2005-10").toString());
+        assertEquals("+pubDate:[20051006 TO 99999999]", kf.since("2005-1006").toString());
+        assertEquals("+pubDate:[20051006 TO 99999999]", kf.since("2005-10-06").toString());
+        
+        assertEquals("+pubDate:[20050000 TO 20059999]", kf.date("2005").toString());
+        assertEquals("+pubDate:[20051000 TO 20051099]", kf.date("200510").toString());
+        assertEquals("+pubDate:[20051000 TO 20051099]", kf.date("2005-10").toString());
+        assertEquals("+pubDate:20051006", kf.date("2005-1006").toString());
+        assertEquals("+pubDate:20051006", kf.date("2005-10-06").toString());
+    };
+    
+    @Test
+    public void rangeFailure () throws IOException {
+        CollectionBuilder kf = new CollectionBuilder();
+        assertEquals("", kf.between("aaaa-bb-cc", "aaaabbcc").toString());
+        assertEquals("", kf.till("aaaa-bb-cc").toString());
+        assertEquals("", kf.since("aaaa-bb-cc").toString());
+        assertEquals("", kf.date("aaaa-bb-cc").toString());
+    };
+
+
+    // TODO: More extensive testing!
+};
diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestKorapCollectionLegacy.java b/src/test/java/de/ids_mannheim/korap/collection/TestKorapCollectionLegacy.java
index eb09d8a..514cb28 100644
--- a/src/test/java/de/ids_mannheim/korap/collection/TestKorapCollectionLegacy.java
+++ b/src/test/java/de/ids_mannheim/korap/collection/TestKorapCollectionLegacy.java
@@ -5,7 +5,6 @@
 import de.ids_mannheim.korap.KorapIndex;
 import de.ids_mannheim.korap.index.FieldDocument;
 import de.ids_mannheim.korap.KorapCollection;
-import de.ids_mannheim.korap.KorapFilter;
 import de.ids_mannheim.korap.KorapResult;
 import de.ids_mannheim.korap.KorapQuery;
 import de.ids_mannheim.korap.collection.BooleanFilter;
@@ -43,7 +42,7 @@
 	};
 	ki.commit();
 
-	KorapFilter kf = new KorapFilter();
+	CollectionBuilder kf = new CollectionBuilder();
 
 	// Create Virtual collections:
 	KorapCollection kc = new KorapCollection(ki);
@@ -118,7 +117,7 @@
 	    ki.commit();
 	};
 
-	KorapFilter kf = new KorapFilter();
+	CollectionBuilder kf = new CollectionBuilder();
 
 	// Create Virtual collections:
 	KorapCollection kc = new KorapCollection(ki);
@@ -198,7 +197,7 @@
 
 	ki.commit();
 
-	KorapFilter kf = new KorapFilter();
+	CollectionBuilder kf = new CollectionBuilder();
 
 	// Create Virtual collections:
 	KorapCollection kc = new KorapCollection(ki);
diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestKorapFilter.java b/src/test/java/de/ids_mannheim/korap/collection/TestKorapFilter.java
deleted file mode 100644
index f89145f..0000000
--- a/src/test/java/de/ids_mannheim/korap/collection/TestKorapFilter.java
+++ /dev/null
@@ -1,88 +0,0 @@
-package de.ids_mannheim.korap.collection;
-
-import java.util.*;
-import java.io.*;
-
-import org.apache.lucene.util.Version;
-import org.apache.lucene.util.BytesRef;
-import org.apache.lucene.util.Bits;
-
-import static org.junit.Assert.*;
-import org.junit.Test;
-import org.junit.Ignore;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
-
-import de.ids_mannheim.korap.KorapFilter;
-
-@RunWith(JUnit4.class)
-public class TestKorapFilter {
-
-    @Test
-    public void filterExample () throws IOException {
-
-	KorapFilter kf = new KorapFilter();
-
-	assertEquals("+textClass:tree", kf.and("textClass","tree").toString());
-	assertEquals("+textClass:tree +textClass:sport", kf.and("textClass","tree").and("textClass","sport").toString());
-	assertEquals("+textClass:tree +textClass:sport textClass:news", kf.and("textClass","tree").and("textClass","sport").or("textClass","news").toString());
-	assertEquals("+textClass:tree +textClass:sport +textClass:news", kf.and("textClass", "tree", "sport", "news").toString());
-
-	assertEquals("corpusID:c-1 corpusID:c-2 corpusID:c-3", kf.or("corpusID", "c-1", "c-2", "c-3").toString());
-    };
-
-    @Test
-    public void rangeExample () throws IOException {
-
-	KorapFilter kf = new KorapFilter();
-
-	assertEquals("+pubDate:[20030604 TO 20030899]", kf.between("2003-06-04", "2003-08-99").toString());
-	assertEquals("+pubDate:[0 TO 20030604]", kf.till("2003-06-04").toString());
-	assertEquals("+pubDate:[20030604 TO 99999999]", kf.since("2003-06-04").toString());
-	assertEquals("+pubDate:20030604", kf.date("2003-06-04").toString());
-    };
-
-    @Test
-    public void rangeLimited () throws IOException {
-
-	KorapFilter kf = new KorapFilter();
-
-	assertEquals("+pubDate:[20050000 TO 20099999]", kf.between("2005", "2009").toString());
-       	assertEquals("+pubDate:[20051000 TO 20090899]", kf.between("200510", "200908").toString());
-	assertEquals("+pubDate:[20051000 TO 20090899]", kf.between("2005-10", "2009-08").toString());
-	assertEquals("+pubDate:[20051006 TO 20090803]", kf.between("2005-1006", "2009-0803").toString());
-	assertEquals("+pubDate:[20051006 TO 20090803]", kf.between("2005-10-06", "2009-08-03").toString());
-
-	assertEquals("+pubDate:[0 TO 20059999]", kf.till("2005").toString());
-	assertEquals("+pubDate:[0 TO 20051099]", kf.till("200510").toString());
-	assertEquals("+pubDate:[0 TO 20051099]", kf.till("2005-10").toString());
-	assertEquals("+pubDate:[0 TO 20051006]", kf.till("2005-1006").toString());
-	assertEquals("+pubDate:[0 TO 20051006]", kf.till("2005-10-06").toString());
-
-	assertEquals("+pubDate:[20050000 TO 99999999]", kf.since("2005").toString());
-	assertEquals("+pubDate:[20051000 TO 99999999]", kf.since("200510").toString());
-	assertEquals("+pubDate:[20051000 TO 99999999]", kf.since("2005-10").toString());
-	assertEquals("+pubDate:[20051006 TO 99999999]", kf.since("2005-1006").toString());
-	assertEquals("+pubDate:[20051006 TO 99999999]", kf.since("2005-10-06").toString());
-
-	assertEquals("+pubDate:[20050000 TO 20059999]", kf.date("2005").toString());
-	assertEquals("+pubDate:[20051000 TO 20051099]", kf.date("200510").toString());
-	assertEquals("+pubDate:[20051000 TO 20051099]", kf.date("2005-10").toString());
-	assertEquals("+pubDate:20051006", kf.date("2005-1006").toString());
-	assertEquals("+pubDate:20051006", kf.date("2005-10-06").toString());
-    };
-
-    @Test
-    public void rangeFailure () throws IOException {
-
-	KorapFilter kf = new KorapFilter();
-	assertEquals("", kf.between("aaaa-bb-cc", "aaaabbcc").toString());
-	assertEquals("", kf.till("aaaa-bb-cc").toString());
-	assertEquals("", kf.since("aaaa-bb-cc").toString());
-	assertEquals("", kf.date("aaaa-bb-cc").toString());
-    };
-
-
-    // TODO: More extensive testing!
-
-};
diff --git a/src/test/java/de/ids_mannheim/korap/search/TestKorapSearch.java b/src/test/java/de/ids_mannheim/korap/search/TestKorapSearch.java
index e1aae5e..b5f3dcf 100644
--- a/src/test/java/de/ids_mannheim/korap/search/TestKorapSearch.java
+++ b/src/test/java/de/ids_mannheim/korap/search/TestKorapSearch.java
@@ -11,7 +11,7 @@
 import de.ids_mannheim.korap.KorapIndex;
 import de.ids_mannheim.korap.index.FieldDocument;
 import de.ids_mannheim.korap.index.SearchContext;
-import de.ids_mannheim.korap.KorapFilter;
+import de.ids_mannheim.korap.collection.CollectionBuilder;
 import de.ids_mannheim.korap.KorapResult;
 import java.nio.file.Files;
 import java.nio.file.FileSystem;
@@ -97,7 +97,7 @@
 	        new KorapQuery("tokens").seg("s:Buchstaben")
         );
         ks.getCollection().filter(
-            new KorapFilter().and("textClass", "reisen")
+            new CollectionBuilder().and("textClass", "reisen")
         );
         ks.setCount(3);
         ks.setStartIndex(5);
@@ -913,7 +913,7 @@
         assertEquals(0, kc.numberOf("documents"));
 
         kc.extend(
-            new KorapFilter().or("corpusSigle", "BZK")
+            new CollectionBuilder().or("corpusSigle", "BZK")
         );
         ks.setCollection(kc);
         assertEquals(1, kc.numberOf("documents"));
diff --git a/src/test/java/de/ids_mannheim/korap/search/TestMetaFields.java b/src/test/java/de/ids_mannheim/korap/search/TestMetaFields.java
index 34b1f29..387b2cb 100644
--- a/src/test/java/de/ids_mannheim/korap/search/TestMetaFields.java
+++ b/src/test/java/de/ids_mannheim/korap/search/TestMetaFields.java
@@ -11,7 +11,6 @@
 import de.ids_mannheim.korap.KorapIndex;
 import de.ids_mannheim.korap.index.FieldDocument;
 import de.ids_mannheim.korap.index.SearchContext;
-import de.ids_mannheim.korap.KorapFilter;
 import de.ids_mannheim.korap.KorapResult;
 import java.nio.file.Files;
 import java.nio.file.FileSystem;