diff --git a/FKala.Core/KalaQl/KalaQuery.cs b/FKala.Core/KalaQl/KalaQuery.cs
index 622ac55..2654ccc 100644
--- a/FKala.Core/KalaQl/KalaQuery.cs
+++ b/FKala.Core/KalaQl/KalaQuery.cs
@@ -149,7 +149,7 @@ public KalaQuery FromQuery(string queryText)
                 case "Insert":
                     return new Op_Insert(line, fields[1].Trim(':'), fields[2], fields[3]);
                 case "Expr":
-                    return new Op_Expresso(line, fields[1].Trim(':'), fields[2]);
+                    return new Op_Expresso(line, fields[1].Trim(':'), fields[2].Replace('\'', '"'));
                 case "Publ":
                     return new Op_Publish(line, fields[1].Split(",", StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries).ToList(), ParsePublishMode(fields[2]));
                 case "Mgmt":
diff --git a/FKala.Core/KalaQl/Op_BaseQuery.cs b/FKala.Core/KalaQl/Op_BaseQuery.cs
index d42743a..954dc56 100644
--- a/FKala.Core/KalaQl/Op_BaseQuery.cs
+++ b/FKala.Core/KalaQl/Op_BaseQuery.cs
@@ -37,12 +37,8 @@ public override bool CanExecute(KalaQlContext context)
 
         public override void Execute(KalaQlContext context)
         {
-            //var result = context.DataLayer.LoadData(this.Measurement, this.StartTime, this.EndTime, CacheResolution, NewestOnly, DoSortRawFiles);
+            var result = context.DataLayer.LoadData(this.Measurement, this.StartTime, this.EndTime, CacheResolution, NewestOnly, context, DontInvalidateCache_ForUseWhileCacheRebuild).ToList();
 
-//TODODODODODODDODODO REBUILD IST SOMIT DEFEKT            
-            // bei ForceRebuild auch ohne Ausgabe etc. den Rebuild durchführen, ..was erst geschieht beim Materialisieren                        
-            //if (CacheResolution.ForceRebuild) result = result.ToList();
-            
             context.IntermediateDatasources.Add(
                 new ResultPromise()
                 {
@@ -52,11 +48,24 @@ public override void Execute(KalaQlContext context)
                     Creator = this,
                     ResultsetFactory = () =>
                     {
-                        var result = context.DataLayer.LoadData(this.Measurement, this.StartTime, this.EndTime, CacheResolution, NewestOnly, context, DontInvalidateCache_ForUseWhileCacheRebuild);
-                        return result;
+                        // source file streaming
+                        //var result = context.DataLayer.LoadData(this.Measurement, this.StartTime, this.EndTime, CacheResolution, NewestOnly, context, DontInvalidateCache_ForUseWhileCacheRebuild);
+                        //return result;
+
+                        //in-mem copy
+                        return Clone(result);
                     }
                 });
             this.hasExecuted = true;
         }
+
+
+        private IEnumerable<DataPoint> Clone(IEnumerable<DataPoint> input)
+        {
+            foreach(var dp in input)
+            {
+                yield return dp.Clone();
+            }
+        }
     }
 }
diff --git a/FKala.Core/KalaQl/Op_Expresso.cs b/FKala.Core/KalaQl/Op_Expresso.cs
index 47b3dd8..c0fd08a 100644
--- a/FKala.Core/KalaQl/Op_Expresso.cs
+++ b/FKala.Core/KalaQl/Op_Expresso.cs
@@ -8,6 +8,7 @@
 using Newtonsoft.Json.Linq;
 using System;
 using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics.Arm;
 
 namespace FKala.Core.KalaQl
 {
@@ -30,7 +31,17 @@ public Op_Expresso(string? line, string name, string expresso) : base(line)
             UnknownIdInfo = Interpreter.DetectIdentifiers(Expresso);
             var parameters = UnknownIdInfo.UnknownIdentifiers
                 .Order()
-                .Select(identifier => new Parameter(identifier, typeof(DataPoint)));
+                .Select(identifier => {
+                    if (identifier == "previousInput")
+                    {
+                        return new Parameter(identifier, typeof(Dictionary<string, DataPoint>));
+                    } 
+                    else
+                    {
+                        return new Parameter(identifier, typeof(DataPoint));
+                    }
+                    
+                });
 
             Lambda = Interpreter.Parse(Expresso, parameters.ToArray());
         }
@@ -40,7 +51,10 @@ public class Skip { }
         public override bool CanExecute(KalaQlContext context)
         {
             var IdInfo = Interpreter.DetectIdentifiers(Expresso);
-            return IdInfo.UnknownIdentifiers.All(id => context.IntermediateDatasources.Any(res => res.Name == id));
+            var missingIdentifiers = IdInfo.UnknownIdentifiers.ToList();
+            missingIdentifiers.Remove("previousInput");
+            missingIdentifiers.Remove("previousOutput");
+            return missingIdentifiers.All(id => context.IntermediateDatasources.Any(res => res.Name == id));
         }
 
         public override void Execute(KalaQlContext context)
@@ -64,19 +78,34 @@ public override void Execute(KalaQlContext context)
             this.hasExecuted = true;
 
         }
-        DateTime firstStartTime;
+        
         public IEnumerable<DataPoint> ExecuteInternal(KalaQlContext context, IEnumerable<ResultPromise> datenquellen)
         {
+            Dictionary<string, DataPoint> previousInput = new Dictionary<string, DataPoint>();
+            foreach (string id in UnknownIdInfo.UnknownIdentifiers)
+            {
+                if (id == "previousInput") continue;
+                previousInput[id] = Pools.DataPoint.Get();
+                previousInput[id].Value = 0;
+            }
+           
+
+            var pInitial = Pools.DataPoint.Get();
+            pInitial.Value = 0;
+            DataPoint? previousOutput = pInitial;
             var combined = new List<(DateTime Timestamp, int ListIndex, ResultPromise Item)>();
-            bool isFirstStartTime = true;
             foreach (var timeSynchronizedItems in DatasetsCombiner2.CombineSynchronizedResults(datenquellen.ToList()))
             {
-                if (isFirstStartTime)
-                {
-                    firstStartTime = timeSynchronizedItems.First().DataPoint.StartTime;
-                }
+                
                 var missingIdentifiers = UnknownIdInfo.UnknownIdentifiers.ToList();
-                var paramValues = new List<Parameter>();
+                var paramValues = new List<Parameter>
+                {
+                    new Parameter("previousInput", previousInput),
+                    new Parameter("previousOutput", previousOutput)
+                };
+                missingIdentifiers.Remove("previousInput");
+                missingIdentifiers.Remove("previousOutput");
+
                 foreach (var si in timeSynchronizedItems)
                 {
                     paramValues.Add(new Parameter(si.Result.Name, si.DataPoint));
@@ -89,7 +118,12 @@ public IEnumerable<DataPoint> ExecuteInternal(KalaQlContext context, IEnumerable
                     localDps.Add(ldp);
                     paramValues.Add(new Parameter(mi, ldp));
                 }
-
+                var nextPreviousInput = new Dictionary<string, DataPoint>();
+                foreach (var pv in paramValues)
+                {
+                    if (pv.Name == "previousInput") continue;
+                    nextPreviousInput[pv.Name] = ((DataPoint)pv.Value).Clone();
+                }
                 object? result = Lambda.Invoke(paramValues);
                 if (result is Skip)
                 {
@@ -102,8 +136,17 @@ public IEnumerable<DataPoint> ExecuteInternal(KalaQlContext context, IEnumerable
                     currentDataPoint.StartTime = timeSynchronizedItems.Key.Item1;
                     currentDataPoint.EndTime = timeSynchronizedItems.Key.Item2;
                     currentDataPoint.Value = expressoResultValue;
+                    previousOutput.Value = expressoResultValue;
                     yield return currentDataPoint;
                 }
+                
+                //foreach (var item in previousInput.Values)
+                //{
+                //    Pools.DataPoint.Return(item);
+                //}
+                previousInput = nextPreviousInput;
+
+               
             }
         }
     }
diff --git a/FKala.Core/Model/DataPoint.cs b/FKala.Core/Model/DataPoint.cs
index f57ae13..3044a42 100644
--- a/FKala.Core/Model/DataPoint.cs
+++ b/FKala.Core/Model/DataPoint.cs
@@ -56,5 +56,16 @@ public string AsLineData(string measurement)
         {
             return $"{measurement} {StartTime.ToString("yyyy-MM-ddTHH:mm:ss.fffffff")} {Value?.ToString() ?? ValueText}";
         }
+
+        public DataPoint Clone()
+        {
+            var ret = Pools.DataPoint.Get();
+            ret.StartTime = new DateTime(StartTime.Ticks);
+            ret.EndTime = new DateTime(EndTime.Ticks);
+            ret.Value = Value;
+            ret.ValueText = ValueText;
+            ret.Source = Source;
+            return ret;
+        }
     }
 }
\ No newline at end of file