diff --git a/Changes b/Changes
index dbea656..9ed843c 100644
--- a/Changes
+++ b/Changes
@@ -1,4 +1,4 @@
-0.58.0 2018-08-21
+0.58.0 2018-08-23
     - [feature] Implemented referencing cached collection (margaretha)
     - [feature] Implemented deserialization of collection with array values
       and cache option (margaretha)
@@ -15,6 +15,9 @@
     - [feature] Adding loading namedVC from gz (margaretha)
     - [bugfix] Fixed VC deserialization and double negations in 
       CollectionBuilder.group (margaretha)
+    - [cleanup] Move caching mechanism to toFilter() phase (diewald)
+    - [cleanup] Rewrite test suite for caching to be part of
+      regular test suite (diewald)
 
 0.57 2018-04-05
     - [feature] Support text queries in metadata
diff --git a/pom.xml b/pom.xml
index d73ed2c..a3e8b08 100644
--- a/pom.xml
+++ b/pom.xml
@@ -289,7 +289,6 @@
 						<exclude>**/TestWPDIndex.java</exclude>
 						<exclude>**/TestRealIndex.java</exclude>
 						<exclude>**/TestSampleIndex.java</exclude>
-						<exclude>**/TestVCCaching.java</exclude>
 					</excludes>
 				</configuration>
 			</plugin>
diff --git a/src/main/java/de/ids_mannheim/korap/KrillCollection.java b/src/main/java/de/ids_mannheim/korap/KrillCollection.java
index 33811a5..6cdcdca 100644
--- a/src/main/java/de/ids_mannheim/korap/KrillCollection.java
+++ b/src/main/java/de/ids_mannheim/korap/KrillCollection.java
@@ -67,6 +67,8 @@
     private CollectionBuilder cb = new CollectionBuilder();
     private CollectionBuilder.Interface cbi;
     private byte[] pl = new byte[4];
+
+	private Filter prefiltered = null;
     // private static ByteBuffer bb = ByteBuffer.allocate(4);
 
     // Logger
@@ -119,7 +121,7 @@
             }
             else {
                 this.addError(StatusCodes.MISSING_COLLECTION,
-                        "Collection is not found.");
+                        "Collection is not found");
                 this.fromBuilder(this.build().nothing());
             }
         }
@@ -160,6 +162,7 @@
      */
     public KrillCollection fromKoral (String jsonString) throws QueryException {
         ObjectMapper mapper = new ObjectMapper();
+		this.prefiltered = null;
         try {
             this.fromKoral((JsonNode) mapper.readTree(jsonString));
         }
@@ -172,6 +175,60 @@
     };
 
 
+	public KrillCollection fromCache (String ref) throws QueryException {
+        Properties prop = KrillProperties.loadDefaultProperties();
+		this.prefiltered = null;
+	
+        if (prop == null) {
+            this.addError(StatusCodes.MISSING_KRILL_PROPERTIES,
+						  "krill.properties is not found.");
+			return null;
+        }
+
+        String namedVCPath = prop.getProperty("krill.namedVC");
+
+		if (!namedVCPath.endsWith("/")) {
+            namedVCPath += "/";
+        };
+
+		String fileName = namedVCPath + ref + ".jsonld";
+		File file; 
+        String json = null;
+        if ((file= new File(fileName)).exists()) {
+            try (FileInputStream fis = new FileInputStream(file)) {
+                json = IOUtils.toString(fis,"utf-8");
+            }
+            catch (IOException e) {
+                this.addError(StatusCodes.READING_COLLECTION_FAILED,
+                        e.getMessage());
+				return this;
+            }
+        }
+        // slower than plain text, but save space
+        else if ((file = new File(fileName + ".gz")).exists()){
+            try (GZIPInputStream gzipInputStream =
+                    new GZIPInputStream(new FileInputStream(file));
+                    ByteArrayOutputStream bos =
+                            new ByteArrayOutputStream(512);) {
+                bos.write(gzipInputStream);
+                json = bos.toString("utf-8");
+            }
+            catch (IOException e) {
+                this.addError(StatusCodes.READING_COLLECTION_FAILED,
+                        e.getMessage());
+				return this;
+            }
+        }
+        else{
+            this.addError(StatusCodes.MISSING_COLLECTION,
+                    "Collection is not found " + fileName);
+			return this;
+        };
+
+        return this.fromKoral(json);
+	};
+
+
     /**
      * Import the "collection" part of a KoralQuery.
      * 
@@ -182,13 +239,18 @@
      */
     public KrillCollection fromKoral (JsonNode json) throws QueryException {
         this.json = json;
+		this.prefiltered = null;
         return this.fromBuilder(this._fromKoral(json));
     };
 
 
     // Create collection from KoralQuery
     private CollectionBuilder.Interface _fromKoral (JsonNode json)
-            throws QueryException {
+		throws QueryException {
+
+		if (json.has("collection")) {
+			return this._fromKoral(json.at("/collection"));
+		};
 
         if (!json.has("@type")) {
             throw new QueryException(701,
@@ -320,9 +382,7 @@
         }
 
         // nested group
-        else if (type.equals("koral:docGroup"))
-
-        {
+        else if (type.equals("koral:docGroup")) {
 
             if (!json.has("operands") || !json.get("operands").isArray())
                 throw new QueryException(842,
@@ -347,8 +407,10 @@
             };
             return group;
         }
+
         // vc reference
         else if (type.equals("koral:docGroupRef")) {
+			
             if (!json.has("ref")) {
                 throw new QueryException(StatusCodes.MISSING_VC_REFERENCE,
                         "ref is not found");
@@ -358,35 +420,9 @@
             if (ref.isEmpty()) {
                 throw new QueryException(StatusCodes.MISSING_VC_REFERENCE,
                         "ref is empty");
-            }
+            };
 
-            Element element = KrillCollection.cache.get(ref);
-            if (element == null) {
-                String corpusQuery = loadVCFile(ref);
-                if (corpusQuery == null){
-                    return this.build().nothing();
-                }
-                else{
-                    JsonNode node;
-                    try {
-                        node = mapper.readTree(corpusQuery);
-                    }
-                    catch (IOException e) {
-                        throw new QueryException(StatusCodes.INVALID_QUERY, 
-                                "Failed parsing collection query to JsonNode.");
-                    }
-                    if (!node.has("collection")){
-                        this.addError(StatusCodes.MISSING_COLLECTION,
-                                "KoralQuery does not contain a collection.");
-                        return this.build().nothing();
-                    }
-                    return cb.toCacheVC(ref, this._fromKoral(node.at("/collection")));
-                }
-            }
-            else {
-                CachedVCData cc = (CachedVCData) element.getObjectValue();
-                return cb.namedVC(cc);
-            }
+			return this.cb.referTo(ref);
         }
 
 
@@ -394,52 +430,6 @@
         throw new QueryException(813, "Collection type is not supported");
     };
 
-    
-    private String loadVCFile (String ref) {
-        Properties prop = KrillProperties.loadDefaultProperties();
-        if (prop == null) {
-            this.addError(StatusCodes.MISSING_KRILL_PROPERTIES,
-                    "krill.properties is not found.");
-            return null;
-        }
-
-        String namedVCPath = prop.getProperty("krill.namedVC");
-        if (!namedVCPath.endsWith("/")) {
-            namedVCPath += "/";
-        }
-        File file; 
-        String json = null;
-        if ((file= new File(namedVCPath + ref + ".jsonld")).exists()) {
-            try (FileInputStream fis = new FileInputStream(file)) {
-                json = IOUtils.toString(fis,"utf-8");
-            }
-            catch (IOException e) {
-                this.addError(StatusCodes.READING_COLLECTION_FAILED,
-                        e.getMessage());
-            }
-        }
-        // slower than plain text, but save space
-        else if ((file = new File(namedVCPath + ref + ".jsonld.gz")).exists()){
-            try (GZIPInputStream gzipInputStream =
-                    new GZIPInputStream(new FileInputStream(file));
-                    ByteArrayOutputStream bos =
-                            new ByteArrayOutputStream(512);) {
-                bos.write(gzipInputStream);
-                json = bos.toString("utf-8");
-            }
-            catch (IOException e) {
-                this.addError(StatusCodes.READING_COLLECTION_FAILED,
-                        e.getMessage());
-            }
-        }
-        else{
-            this.addError(StatusCodes.MISSING_COLLECTION,
-                    "Collection is not found.");
-        }
-
-        return json;
-    }
-
     /**
      * Set the collection from a {@link CollectionBuilder} object.
      * 
@@ -447,6 +437,7 @@
      *            The CollectionBuilder object.
      */
     public KrillCollection fromBuilder (CollectionBuilder.Interface cbi) {
+		this.prefiltered = null;
         this.cbi = cbi;
         return this;
     };
@@ -485,6 +476,7 @@
      * @return The {@link KrillCollection} object for chaining.
      */
     public KrillCollection filterUIDs (String ... uids) {
+		this.prefiltered = null;
         CollectionBuilder.Group cbg = this.cb.orGroup();
         for (String uid : uids) {
             cbg.with(this.cb.term("UID", uid));
@@ -496,10 +488,15 @@
     /**
      * Serialize collection to a {@link Filter} object.
      */
-    public Filter toFilter () {
-        if (this.cbi == null) return null;
-
-        return this.cbi.toFilter();
+    public Filter toFilter () throws QueryException {
+        if (this.cbi == null)
+			return null;
+	
+		if (this.prefiltered != null)
+			return this.prefiltered;
+		
+		this.prefiltered = this.cbi.toFilter();
+		return this.prefiltered;
     };
 
 
@@ -515,7 +512,7 @@
 
 
     /**
-     * Generate a string representatio of the virtual collection.
+     * Generate a string representation of the virtual collection.
      * 
      * <strong>Warning</strong>: This currently does not generate a
      * valid
@@ -524,10 +521,15 @@
      * @return A string representation of the virtual collection.
      */
     public String toString () {
-        Filter filter = this.toFilter();
-        if (filter == null) return "";
-
-        return (this.isNegative() ? "-" : "") + filter.toString();
+		try {
+			Filter filter = this.toFilter();
+			if (filter == null) return "";
+			return (this.isNegative() ? "-" : "") + filter.toString();
+		}
+		catch (QueryException qe) {
+            log.warn(qe.getLocalizedMessage());
+		};
+		return "";
     };
 
 
@@ -557,7 +559,7 @@
      *         virtual collection.
      * @throws IOException
      */
-    public FixedBitSet bits (LeafReaderContext atomic) throws IOException {
+    public FixedBitSet bits (LeafReaderContext atomic) throws IOException, QueryException {
 
         LeafReader r = atomic.reader();
         FixedBitSet bitset = new FixedBitSet(r.maxDoc());
@@ -590,46 +592,45 @@
      * @throws IOException
      */
     public DocIdSet getDocIdSet (LeafReaderContext atomic, Bits acceptDocs)
-            throws IOException {
+		throws IOException, QueryException {
 
         int maxDoc = atomic.reader().maxDoc();
         FixedBitSet bitset = new FixedBitSet(maxDoc);
 
         Filter filter;
-        if (this.cbi == null || (filter = this.cbi.toFilter()) == null) {
-            if (acceptDocs == null) return null;
+		if (this.cbi == null || (filter = this.toFilter()) == null) {
+			if (acceptDocs == null) return null;
+			bitset.set(0, maxDoc);
+		}
+		else {
 
-            bitset.set(0, maxDoc);
-        }
-        else {
+			// Init vector
+			DocIdSet docids = filter.getDocIdSet(atomic, null);
+			DocIdSetIterator filterIter =
+				(docids == null) ? null : docids.iterator();
+				
+			if (filterIter == null) {
+				if (!this.cbi.isNegative()) return null;
 
-            // Init vector
-            DocIdSet docids = filter.getDocIdSet(atomic, null);
-            DocIdSetIterator filterIter =
-                    (docids == null) ? null : docids.iterator();
+				bitset.set(0, maxDoc);
+			}
+			else {
+				// Or bit set
+				bitset.or(filterIter);
+					
+				// Revert for negation
+				if (this.cbi.isNegative()) bitset.flip(0, maxDoc);
+			};
+		};
 
-            if (filterIter == null) {
-                if (!this.cbi.isNegative()) return null;
-
-                bitset.set(0, maxDoc);
-            }
-            else {
-                // Or bit set
-                bitset.or(filterIter);
-
-                // Revert for negation
-                if (this.cbi.isNegative()) bitset.flip(0, maxDoc);
-            };
-        };
-
-        if (DEBUG) {
-            log.debug("Bit set is  {}", _bits(bitset));
-            log.debug("Livedocs is {}", _bits(acceptDocs));
+		if (DEBUG) {
+			log.debug("Bit set is  {}", _bits(bitset));
+			log.debug("Livedocs is {}", _bits(acceptDocs));
         };
 
         // Remove deleted docs
         return (DocIdSet) BitsFilteredDocIdSet
-                .wrap((DocIdSet) new BitDocIdSet(bitset), acceptDocs);
+			.wrap((DocIdSet) new BitDocIdSet(bitset), acceptDocs);
     };
 
 
@@ -694,7 +695,12 @@
 
         // Something went wrong
         catch (IOException e) {
-            log.warn(e.getMessage());
+            log.warn(e.getLocalizedMessage());
+		}
+
+		// E.g. reference corpus not found
+        catch (QueryException e) {
+            log.warn(e.getLocalizedMessage());
         };
 
         return occurrences;
@@ -792,6 +798,9 @@
         }
         catch (IOException e) {
             log.warn(e.getLocalizedMessage());
+		}
+        catch (QueryException e) {
+            log.warn(e.getLocalizedMessage());
         };
         return docCount;
     };
@@ -806,7 +815,7 @@
     };
 
 
-    public void storeInCache (String cacheKey) throws IOException {
+    public void storeInCache (String cacheKey) throws IOException, QueryException {
         if (cacheKey ==null || cacheKey.isEmpty()) {
             this.addError(StatusCodes.MISSING_ID,
                     "Collection name is required for caching.");
@@ -826,7 +835,7 @@
 
         CachedVCData cc = new CachedVCData(docIdMap);
         cache.put(new Element(cacheKey, cc));
-        this.cbi = cb.namedVC(cc);
+        this.cbi = cb.namedVC(cacheKey, cc);
     }
     
     /*
diff --git a/src/main/java/de/ids_mannheim/korap/KrillIndex.java b/src/main/java/de/ids_mannheim/korap/KrillIndex.java
index dfcea3a..e47589e 100644
--- a/src/main/java/de/ids_mannheim/korap/KrillIndex.java
+++ b/src/main/java/de/ids_mannheim/korap/KrillIndex.java
@@ -1577,7 +1577,12 @@
         catch (IOException e) {
             kr.addError(600, "Unable to read index", e.getLocalizedMessage());
             log.warn(e.getLocalizedMessage());
-        };
+		}
+
+		catch (QueryException e) {
+            kr.addError(e.getErrorCode(),e.getLocalizedMessage());
+            log.warn(e.getLocalizedMessage());			
+		};
 
         // Stop timer thread
         tthread.stopTimer();
@@ -1763,7 +1768,11 @@
         catch (IOException e) {
             mc.addError(600, "Unable to read index", e.getLocalizedMessage());
             log.warn(e.getLocalizedMessage());
-        };
+		}
+		catch (QueryException e) {
+            mc.addError(e.getErrorCode(),e.getLocalizedMessage());
+            log.warn(e.getLocalizedMessage());			
+		};
 
         mc.close();
         return mc;
diff --git a/src/main/java/de/ids_mannheim/korap/collection/CachedVCData.java b/src/main/java/de/ids_mannheim/korap/collection/CachedVCData.java
index 8b73a45..ca97d52 100644
--- a/src/main/java/de/ids_mannheim/korap/collection/CachedVCData.java
+++ b/src/main/java/de/ids_mannheim/korap/collection/CachedVCData.java
@@ -70,4 +70,8 @@
         }
         return map;
     }
+
+	public String toString () {
+		return this.docIdMap.toString();
+	}
 }
diff --git a/src/main/java/de/ids_mannheim/korap/collection/CachedVCFilter.java b/src/main/java/de/ids_mannheim/korap/collection/CachedVCFilter.java
index 24ce0b0..1c35233 100644
--- a/src/main/java/de/ids_mannheim/korap/collection/CachedVCFilter.java
+++ b/src/main/java/de/ids_mannheim/korap/collection/CachedVCFilter.java
@@ -16,8 +16,10 @@
 public class CachedVCFilter extends Filter {
 
     private CachedVCData cachedCollection;
+	private String cacheKey;
 
-    public CachedVCFilter (CachedVCData cachedCollection) {
+    public CachedVCFilter (String cacheKey, CachedVCData cachedCollection) {
+		this.cacheKey = cacheKey;
         this.cachedCollection = cachedCollection;
     }
 
@@ -26,6 +28,7 @@
             throws IOException {
         DocBits docBits =
                 cachedCollection.getDocIdMap().get(context.hashCode());
+
         if (docBits == null) {
             // does not exist in the cache
             return null;
@@ -33,4 +36,8 @@
         return docBits.createBitDocIdSet();
     }
 
+	@Override
+    public String toString () {
+		return "referTo(cached:" + this.cacheKey + ")";
+    };
 }
diff --git a/src/main/java/de/ids_mannheim/korap/collection/CollectionBuilder.java b/src/main/java/de/ids_mannheim/korap/collection/CollectionBuilder.java
index 3e231bc..3abc0e4 100644
--- a/src/main/java/de/ids_mannheim/korap/collection/CollectionBuilder.java
+++ b/src/main/java/de/ids_mannheim/korap/collection/CollectionBuilder.java
@@ -5,6 +5,9 @@
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Properties;
+import java.io.File;
+import java.io.FileInputStream;
 
 import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
 import org.apache.lucene.queries.TermsFilter;
@@ -17,9 +20,22 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import org.apache.commons.io.IOUtils;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
 import de.ids_mannheim.korap.KrillCollection;
 import de.ids_mannheim.korap.index.TextPrependedTokenStream;
 import de.ids_mannheim.korap.util.KrillDate;
+import de.ids_mannheim.korap.util.QueryException;
+import de.ids_mannheim.korap.util.StatusCodes;
+import de.ids_mannheim.korap.util.KrillProperties;
+
+import net.sf.ehcache.Cache;
+import net.sf.ehcache.CacheManager;
+import net.sf.ehcache.Element;
+
 
 /*
  * TODO: Optimize!
@@ -33,6 +49,10 @@
 
 public class CollectionBuilder {
 
+    public final static CacheManager cacheManager = CacheManager.newInstance();
+    public final static Cache cache = cacheManager.getCache("named_vc");
+
+	
     // Logger
     private final static Logger log = LoggerFactory
             .getLogger(KrillCollection.class);
@@ -124,6 +144,10 @@
                 dateDF.ceil());
     };
 
+	public CollectionBuilder.Interface referTo (String reference) {
+        return new CollectionBuilder.Reference(reference);
+    };
+
 
     public CollectionBuilder.Group andGroup () {
         return new CollectionBuilder.Group(false);
@@ -138,7 +162,7 @@
         public String toString ();
 
 
-        public Filter toFilter ();
+        public Filter toFilter () throws QueryException;
 
 
         public boolean isNegative ();
@@ -214,7 +238,7 @@
 
 		// TODO:
 		//   Currently this treatment is language specific and
-		//    does too mzch, I guess.
+		//    does too much, I guess.
         public Filter toFilter () {
 			PhraseQuery pq = new PhraseQuery();
 			int pos = 0;
@@ -257,6 +281,95 @@
         };
     };
 
+
+    public class Reference implements CollectionBuilder.Interface {
+        private boolean isNegative = false;
+        private String reference;
+		private Map<Integer, DocBits> docIdMap =
+			new HashMap<Integer, DocBits>();
+
+        public Reference (String reference) {
+            this.reference = reference;
+        };
+
+        public Filter toFilter () throws QueryException {
+			ObjectMapper mapper = new ObjectMapper();
+
+			Element element = KrillCollection.cache.get(this.reference);
+            if (element == null) {
+
+                KrillCollection kc = new KrillCollection();
+
+				kc.fromCache(this.reference);
+
+				if (kc.hasErrors()) {
+					throw new QueryException(
+						kc.getError(0).getCode(),
+						kc.getError(0).getMessage()
+						);
+				};
+
+				return new ToCacheVCFilter(
+					this.reference,
+					docIdMap,
+					kc.getBuilder(),
+					kc.toFilter()
+					);
+			}
+            else {
+                CachedVCData cc = (CachedVCData) element.getObjectValue();
+                return new CachedVCFilter(this.reference, cc);
+            }
+        };
+
+
+        public String toString () {
+			return "referTo(" + this.reference + ")";
+        };
+
+
+        public boolean isNegative () {
+            return this.isNegative;
+        };
+
+
+        public CollectionBuilder.Interface not () {
+            this.isNegative = true;
+            return this;
+        };
+
+		private String loadVCFile (String ref) {
+			Properties prop = KrillProperties.loadDefaultProperties();
+			if (prop == null){
+				/*
+				  this.addError(StatusCodes.MISSING_KRILL_PROPERTIES,
+							  "krill.properties is not found.");
+				*/
+				return null;
+			}
+			
+			String namedVCPath = prop.getProperty("krill.namedVC");
+			if (!namedVCPath.endsWith("/")){
+				namedVCPath += "/";
+			}
+			File file = new File(namedVCPath+ref+".jsonld");
+			
+			String json = null;
+			try {
+				FileInputStream fis = new FileInputStream(file);
+				json = IOUtils.toString(fis);
+			}
+			catch (IOException e) {
+				/*
+				this.addError(StatusCodes.MISSING_COLLECTION,
+							  "Collection is not found.");
+				*/
+				return null;
+			}
+			return json;
+		}	
+    };
+	
 	
     public class Group implements CollectionBuilder.Interface {
         private boolean isOptional = false;
@@ -300,7 +413,7 @@
         };
 
 
-        public Filter toFilter () {
+        public Filter toFilter () throws QueryException {
             if (this.operands == null || this.operands.isEmpty())
                 return null;
 
@@ -326,10 +439,16 @@
 
 
         public String toString () {
-            Filter filter = this.toFilter();
-            if (filter == null)
-                return "";
-            return filter.toString();
+			try {
+				Filter filter = this.toFilter();
+				if (filter == null)
+					return "";
+				return filter.toString();
+			}
+			catch (QueryException qe) {
+				log.warn(qe.getLocalizedMessage());
+			};
+			return "";
         };
 
 
@@ -384,16 +503,18 @@
      */
     public class CachedVC implements CollectionBuilder.Interface {
 
+        private String cacheKey;
         private CachedVCData cachedCollection;
         private boolean isNegative = false;
 
-        public CachedVC (CachedVCData cc) {
-            this.cachedCollection = cc;
+        public CachedVC (String vcRef, CachedVCData cc) {
+            this.cacheKey = vcRef;
+			this.cachedCollection = cc;
         }
 
         @Override
         public Filter toFilter () {
-            return new CachedVCFilter(cachedCollection);
+            return new CachedVCFilter(this.cacheKey, cachedCollection);
         }
 
         @Override
@@ -428,7 +549,7 @@
         }
 
         @Override
-        public Filter toFilter () {
+        public Filter toFilter () throws QueryException {
             return new ToCacheVCFilter(cacheKey,docIdMap, child, child.toFilter());
         }
 
@@ -443,9 +564,10 @@
             return this;
         }
     }
-    
-    public Interface namedVC (CachedVCData cc) {
-        return new CollectionBuilder.CachedVC(cc);
+
+	// Maybe irrelevant
+    public Interface namedVC (String vcRef, CachedVCData cc) {
+        return new CollectionBuilder.CachedVC(vcRef, cc);
     }
     
     public Interface toCacheVC (String vcRef, Interface cbi) {
diff --git a/src/main/java/de/ids_mannheim/korap/collection/ToCacheVCFilter.java b/src/main/java/de/ids_mannheim/korap/collection/ToCacheVCFilter.java
index 981d0ed..98d911e 100644
--- a/src/main/java/de/ids_mannheim/korap/collection/ToCacheVCFilter.java
+++ b/src/main/java/de/ids_mannheim/korap/collection/ToCacheVCFilter.java
@@ -21,8 +21,6 @@
  *
  */
 public class ToCacheVCFilter extends Filter {
-
-
     private Filter filter;
     private CollectionBuilder.Interface cbi;
     private String cacheKey;
@@ -66,7 +64,12 @@
 
         KrillCollection.cache.remove(cacheKey);
         KrillCollection.cache.put(new Element(cacheKey, cachedVCData));
+
         return docIdSet;
     }
 
+    @Override
+    public String toString () {
+		return "referTo(" + this.cacheKey + ")";
+    };
 }
diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestCollectionBuilder.java b/src/test/java/de/ids_mannheim/korap/collection/TestCollectionBuilder.java
index 213fb86..f923423 100644
--- a/src/test/java/de/ids_mannheim/korap/collection/TestCollectionBuilder.java
+++ b/src/test/java/de/ids_mannheim/korap/collection/TestCollectionBuilder.java
@@ -86,6 +86,14 @@
 
 
     @Test
+    public void builderReference () throws IOException {
+        CollectionBuilder kc = new CollectionBuilder();
+        assertEquals("referTo(ndiewald/myCorpus)",
+                kc.referTo("ndiewald/myCorpus").toString());
+    };
+	
+
+    @Test
     public void builderTill () throws IOException {
         CollectionBuilder kc = new CollectionBuilder();
         assertEquals("pubDate:[0 TO 20059999]",
diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java b/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java
index d874905..cb633ef 100644
--- a/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java
@@ -2,6 +2,8 @@
 
 import java.io.IOException;
 
+import java.util.Properties;
+
 import de.ids_mannheim.korap.KrillIndex;
 import de.ids_mannheim.korap.KrillCollection;
 import de.ids_mannheim.korap.collection.CollectionBuilder;
@@ -9,6 +11,8 @@
 import de.ids_mannheim.korap.response.Result;
 import de.ids_mannheim.korap.response.SearchContext;
 import de.ids_mannheim.korap.util.StatusCodes;
+import de.ids_mannheim.korap.util.QueryException;
+import de.ids_mannheim.korap.util.KrillProperties;
 import de.ids_mannheim.korap.Krill;
 import de.ids_mannheim.korap.query.QueryBuilder;
 
@@ -18,16 +22,21 @@
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.spans.SpanQuery;
 import org.apache.lucene.search.spans.SpanTermQuery;
+import static de.ids_mannheim.korap.TestSimple.*;
 
 import static org.junit.Assert.*;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
+import net.sf.ehcache.Element;
+
+
 @RunWith(JUnit4.class)
 public class TestKrillCollectionIndex {
     private KrillIndex ki;
 
+    final String path = "/queries/collections/";
 
     @Test
     public void testKrillCollectionWithWrongJson () throws IOException {
@@ -396,7 +405,6 @@
 
         kcn.fromBuilder(cb.term("text", sv));
         assertEquals(1, kcn.docCount());
-
 	};
 
 	@Test
@@ -419,6 +427,133 @@
         assertEquals(1, kcn.docCount());
 	};
 
+	@Test
+    public void testUnknownVC () throws IOException {
+		ki = new KrillIndex();
+		ki.addDoc(createDoc1());
+		ki.commit();
+
+		// This test was adopted from TestVCCaching,
+		// But does not fail anymore for deserialization
+        String json = _getJSONString("unknown-vc-ref.jsonld");
+
+        KrillCollection kc = new KrillCollection(json);
+		assertEquals("referTo(https://korap.ids-mannheim.de/@ndiewald/MyCorpus)", kc.getBuilder().toString());
+
+		// Fails on filtering
+		assertEquals("", kc.toString());
+		
+        QueryBuilder kq = new QueryBuilder("field");
+		
+		Krill krill = new Krill(kq.seg("a").with("b"));
+		krill.setCollection(kc);
+		
+		Result result = krill.apply(ki);
+
+		assertEquals(StatusCodes.MISSING_COLLECTION, result.getError(0).getCode());
+	};
+
+    @Test
+    public void testCache () throws IOException {
+
+		Properties prop = KrillProperties.loadDefaultProperties();
+
+		String vcPath = getClass().getResource(path + "named-vcs").getFile();
+		String tempVC = prop.getProperty("krill.namedVC");
+		prop.setProperty("krill.namedVC", vcPath);
+
+		ki = new KrillIndex();
+		ki.addDoc(createDoc1());
+		ki.addDoc(createDoc2());
+		ki.commit();
+		
+        testManualAddToCache(ki, "named-vcs/named-vc1.jsonld", "named-vc1");
+        testManualAddToCache(ki, "named-vcs/named-vc2.jsonld", "named-vc2");
+        
+        Element element = KrillCollection.cache.get("named-vc1");
+        CachedVCData cc = (CachedVCData) element.getObjectValue();
+        assertTrue(cc.getDocIdMap().size() > 0);
+
+        element = KrillCollection.cache.get("named-vc2");
+        cc = (CachedVCData) element.getObjectValue();
+        assertTrue(cc.getDocIdMap().size() > 0);
+
+		// Check for cache location
+        assertFalse(KrillCollection.cache.isElementInMemory("named-vc1"));
+        assertTrue(KrillCollection.cache.isElementOnDisk("named-vc1"));
+        assertTrue(KrillCollection.cache.isElementInMemory("named-vc2"));
+        assertTrue(KrillCollection.cache.isElementOnDisk("named-vc2"));
+
+        // testSearchCachedVC();
+		String json = _getJSONString("query-with-vc-ref.jsonld");
+		// references named-vc1: ID eq ["doc-2","doc-3"]
+
+		Krill krill = new Krill(json);
+		// TODO: Better keep the reference
+		testManualAddToCache(ki, "named-vcs/named-vc1.jsonld", "named-vc1");
+		assertEquals("referTo(cached:named-vc1)", krill.getCollection().toString());
+
+		Result result = krill.apply(ki);
+		assertEquals("[[a]] c d", result.getMatch(0).getSnippetBrackets());
+		assertEquals(result.getMatch(0).getUID(), 2);
+		assertEquals(result.getMatches().size(), 1);
+		
+        // testAddDocToIndex();
+		ki.addDoc(createDoc3());
+		ki.commit();
+
+		// Cache is removed after index change
+        element = KrillCollection.cache.get("named-vc1");
+        assertNull(element);
+
+		// Restart search - this time it's not precached
+        krill = new Krill(json);
+		assertEquals("referTo(named-vc1)", krill.getCollection().toString());
+		result = krill.apply(ki);
+
+		assertEquals("[[a]] c d", result.getMatch(0).getSnippetBrackets());
+		assertEquals("[[a]] d e", result.getMatch(1).getSnippetBrackets());
+		assertEquals(result.getMatches().size(), 2);
+
+		// testAutoCachingMatch
+		// Check autocache
+		element = KrillCollection.cache.get("named-vc1");
+		cc = (CachedVCData) element.getObjectValue();
+        assertTrue(cc.getDocIdMap().size() > 0);
+		
+		// Because of autocaching, this should work now
+        krill = new Krill(json);
+		assertEquals("referTo(cached:named-vc1)", krill.getCollection().toString());
+		result = krill.apply(ki);
+		assertEquals("[[a]] c d", result.getMatch(0).getSnippetBrackets());
+		assertEquals("[[a]] d e", result.getMatch(1).getSnippetBrackets());
+		assertEquals(result.getMatches().size(), 2);
+
+		// Cache is removed on deletion
+		ki.addDoc(createDoc1());
+		ki.commit();
+
+		// Check cache
+		element = KrillCollection.cache.get("named-vc1");
+        assertNull(element);
+
+		// Rerun query
+        krill = new Krill(json);
+		assertEquals("referTo(named-vc1)", krill.getCollection().toString());
+		result = krill.apply(ki);
+		assertEquals("[[a]] c d", result.getMatch(0).getSnippetBrackets());
+		assertEquals("[[a]] d e", result.getMatch(1).getSnippetBrackets());
+		assertEquals(result.getMatches().size(), 2);
+		
+		prop.setProperty("krill.namedVC", tempVC);
+
+		// testClearCache
+		KrillCollection.cache.removeAll();
+
+        element = KrillCollection.cache.get("named-vc1");
+        assertNull(element);
+    };
+
 
     @Test
     public void filterExampleFromLegacy () throws Exception {
@@ -860,33 +995,59 @@
 
     private FieldDocument createDoc1 () {
         FieldDocument fd = new FieldDocument();
+        fd.addString("UID", "1");
         fd.addString("ID", "doc-1");
         fd.addString("author", "Frank");
         fd.addKeyword("textClass", "Nachricht Kultur Reisen");
         fd.addInt("pubDate", 20051210);
         fd.addText("text", "Der alte  Mann ging über die Straße");
+        fd.addTV("tokens", "a b c", "[(0-1)s:a|i:a|_0$<i>0<i>1|-:t$<i>3]"
+				 + "[(2-3)s:b|i:b|_1$<i>2<i>3]" + "[(4-5)s:c|i:c|_2$<i>4<i>5]");
         return fd;
     };
 
 
     private FieldDocument createDoc2 () {
         FieldDocument fd = new FieldDocument();
-        fd.addString("ID", "doc-2");
+        fd.addString("UID", "2");
+		fd.addString("ID", "doc-2");
         fd.addString("author", "Peter");
         fd.addKeyword("textClass", "Kultur Reisen");
         fd.addInt("pubDate", 20051207);
         fd.addText("text", "Der junge Mann hatte keine andere Wahl");
+        fd.addTV("tokens", "a c d", "[(0-1)s:a|i:a|_0$<i>0<i>1|-:t$<i>3]"
+				 + "[(2-3)s:c|i:c|_1$<i>2<i>3]" + "[(4-5)s:d|i:d|_2$<i>4<i>5]");
         return fd;
     };
 
 
     private FieldDocument createDoc3 () {
         FieldDocument fd = new FieldDocument();
-        fd.addString("ID", "doc-3");
+        fd.addString("UID", "3");
+		fd.addString("ID", "doc-3");
         fd.addString("author", "Sebastian");
         fd.addKeyword("textClass", "Reisen Finanzen");
         fd.addInt("pubDate", 20051216);
         fd.addText("text", "Die Frau und der Mann küssten sich");
+        fd.addTV("tokens", "a d e", "[(0-1)s:a|i:a|_0$<i>0<i>1|-:t$<i>3]"
+				 + "[(2-3)s:d|i:d|_1$<i>2<i>3]" + "[(4-5)s:e|i:e|_2$<i>4<i>5]");
         return fd;
     };
+
+    private void testManualAddToCache (KrillIndex index, String filename, String vcName) throws IOException {
+		String json = _getJSONString(filename);
+
+        KrillCollection kc = new KrillCollection(json);
+        kc.setIndex(index);
+		try {
+			kc.storeInCache(vcName);
+		}
+		catch (QueryException qe) {
+			System.err.println(qe.getLocalizedMessage());
+		};
+    };
+
+    private String _getJSONString (String file) {
+        return getJsonString(getClass().getResource(path + file).getFile());
+    };
 };
diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestVCCaching.java b/src/test/java/de/ids_mannheim/korap/collection/TestVCCaching.java
deleted file mode 100644
index a333f70..0000000
--- a/src/test/java/de/ids_mannheim/korap/collection/TestVCCaching.java
+++ /dev/null
@@ -1,140 +0,0 @@
-package de.ids_mannheim.korap.collection;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertTrue;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.nio.file.Paths;
-import java.util.List;
-
-import org.apache.commons.io.IOUtils;
-import org.apache.lucene.store.MMapDirectory;
-import org.junit.Test;
-
-import com.fasterxml.jackson.databind.JsonNode;
-import com.fasterxml.jackson.databind.ObjectMapper;
-
-import de.ids_mannheim.korap.Krill;
-import de.ids_mannheim.korap.KrillCollection;
-import de.ids_mannheim.korap.KrillIndex;
-import de.ids_mannheim.korap.index.FieldDocument;
-import de.ids_mannheim.korap.response.Message;
-import de.ids_mannheim.korap.util.StatusCodes;
-import net.sf.ehcache.Element;
-
-public class TestVCCaching {
-
-    public static final ObjectMapper mapper = new ObjectMapper();
-    
-    private KrillIndex getSampleIndex () throws IOException {
-        return new KrillIndex(new MMapDirectory(
-                Paths.get(getClass().getResource("/sample-index").getFile())));
-    }
-
-    private KrillIndex index;
-
-    public TestVCCaching () throws IOException {
-        index = getSampleIndex();
-    }
-
-    @Test
-    public void testUnknownVC () throws IOException {
-
-        InputStream is = getClass().getClassLoader()
-                .getResourceAsStream("collection/unknown-vc-ref.jsonld");
-        String json = IOUtils.toString(is,"utf-8");
-
-        KrillCollection kc = new KrillCollection(json);
-        List<Message> messages = kc.getErrors().getMessages();
-        assertEquals(1, messages.size());
-
-        assertEquals(StatusCodes.MISSING_COLLECTION, messages.get(0).getCode());
-    }
-    
-    @Test
-    public void testCache () throws IOException {
-        testManualAddToCache("named-vc/named-vc1.jsonld", "named-vc1");
-        testManualAddToCache("named-vc/named-vc2.jsonld", "named-vc2");
-        
-        Element element = KrillCollection.cache.get("named-vc1");
-        CachedVCData cc = (CachedVCData) element.getObjectValue();
-        assertTrue(cc.getDocIdMap().size() > 0);
-        
-        element = KrillCollection.cache.get("named-vc2");
-        cc = (CachedVCData) element.getObjectValue();
-        assertTrue(cc.getDocIdMap().size() > 0);
-        
-        assertFalse(KrillCollection.cache.isElementInMemory("named-vc1"));
-        assertTrue(KrillCollection.cache.isElementOnDisk("named-vc1"));
-        assertTrue(KrillCollection.cache.isElementInMemory("named-vc2"));
-        assertTrue(KrillCollection.cache.isElementOnDisk("named-vc2"));
-
-        testSearchCachedVC();
-        testAddDocToIndex();
-        testDelDocFromIndex();
-    }
-
-    private void testManualAddToCache (String filename, String vcName) throws IOException {
-        InputStream is = getClass().getClassLoader()
-                .getResourceAsStream(filename);
-        String json = IOUtils.toString(is,"utf-8");
-        is.close();
-
-        KrillCollection kc = new KrillCollection(json);
-        kc.setIndex(index);
-        kc.storeInCache(vcName);
-    }
-
-    private void testSearchCachedVC () throws IOException {
-        InputStream is = getClass().getClassLoader()
-                .getResourceAsStream("collection/query-with-vc-ref.jsonld");
-        String json = IOUtils.toString(is, "utf-8");
-
-        String result = new Krill(json).apply(this.index).toJsonString();
-        System.out.println(json);
-        JsonNode node = mapper.readTree(result);
-        assertTrue(node.at("/matches").size()>0);
-    }
-
-    private void testClearCache () {
-        KrillCollection.cache.removeAll();
-
-        Element element = KrillCollection.cache.get("named-vc1");
-        assertNull(element);
-    }
-
-    public void testAddDocToIndex () throws IOException {
-        testManualAddToCache("named-vc/named-vc1.jsonld", "named-vc1");
-
-        FieldDocument fd = new FieldDocument();
-        fd.addTV("base", "x  y", "[(0-3)s:x]" + // 1
-                "[(3-4)s:y]" // 2
-        );
-        index.addDoc(fd);
-        index.commit();
-        
-        Element element = KrillCollection.cache.get("named-vc1");
-        assertNull(element);
-    }
-    
-    public void testDelDocFromIndex () throws IOException {
-        testManualAddToCache("named-vc/named-vc1.jsonld", "named-vc1");
-
-        index.delDocs("textSigle", "GOE/AGF/00000");
-        index.commit();
-        
-        Element element = KrillCollection.cache.get("named-vc1");
-        assertNull(element);
-    }
-    
-    @Test
-    public void testAutoCachingMatchNe () throws IOException {
-        testSearchCachedVC();
-        // search from cache
-        testSearchCachedVC();
-        testClearCache();
-    }
-}
diff --git a/src/test/resources/named-vc/named-vc1.jsonld b/src/test/resources/named-vc/named-vc1.jsonld
deleted file mode 100644
index 1257134..0000000
--- a/src/test/resources/named-vc/named-vc1.jsonld
+++ /dev/null
@@ -1,10 +0,0 @@
-{"collection": {
-    "@type": "koral:doc",
-    "key": "textSigle",
-    "match": "match:ne",
-    "type" : "type:string",
-    "value": [
-        "GOE/AGF/00000",
-        "GOE/AGA/01784"
-    ]
-}}
diff --git a/src/test/resources/collection/availability-all.jsonld b/src/test/resources/queries/collections/availability-all.jsonld
similarity index 100%
rename from src/test/resources/collection/availability-all.jsonld
rename to src/test/resources/queries/collections/availability-all.jsonld
diff --git a/src/test/resources/queries/collections/named-vcs/named-vc1.jsonld b/src/test/resources/queries/collections/named-vcs/named-vc1.jsonld
new file mode 100644
index 0000000..ae2bc82
--- /dev/null
+++ b/src/test/resources/queries/collections/named-vcs/named-vc1.jsonld
@@ -0,0 +1,9 @@
+{"collection": {
+    "@type": "koral:doc",
+    "key": "UID",
+    "type" : "type:string",
+    "value": [
+        2,
+        3
+    ]
+}}
diff --git a/src/test/resources/named-vc/named-vc2.jsonld b/src/test/resources/queries/collections/named-vcs/named-vc2.jsonld
similarity index 100%
rename from src/test/resources/named-vc/named-vc2.jsonld
rename to src/test/resources/queries/collections/named-vcs/named-vc2.jsonld
diff --git a/src/test/resources/collection/query-with-vc-ref.jsonld b/src/test/resources/queries/collections/query-with-vc-ref.jsonld
similarity index 72%
rename from src/test/resources/collection/query-with-vc-ref.jsonld
rename to src/test/resources/queries/collections/query-with-vc-ref.jsonld
index ee0bb66..86547ac 100644
--- a/src/test/resources/collection/query-with-vc-ref.jsonld
+++ b/src/test/resources/queries/collections/query-with-vc-ref.jsonld
@@ -3,9 +3,8 @@
     "wrap":{
       "@type":"koral:term",
       "layer":"orth",
-      "key":"der",
-      "match":"match:eq",
-      "foundry":"opennlp"
+      "key":"a",
+      "match":"match:eq"
     }
   },
   "collection": {
diff --git a/src/test/resources/collection/unknown-vc-ref.jsonld b/src/test/resources/queries/collections/unknown-vc-ref.jsonld
similarity index 100%
rename from src/test/resources/collection/unknown-vc-ref.jsonld
rename to src/test/resources/queries/collections/unknown-vc-ref.jsonld