diff --git a/Core/Core.csproj b/Core/Core.csproj
index e36b53d..cad1790 100644
--- a/Core/Core.csproj
+++ b/Core/Core.csproj
@@ -47,6 +47,23 @@
   <ItemGroup>
     <Compile Include="Config.cs" />
     <Compile Include="DataObject.cs" />
+    <Compile Include="DB\conditions\AbstractCondition.cs" />
+    <Compile Include="DB\ColumnOrValue.cs" />
+    <Compile Include="DB\ColumnSpec.cs" />
+    <Compile Include="DB\conditions\ComparisonCondition.cs" />
+    <Compile Include="DB\conditions\ComparisonType.cs" />
+    <Compile Include="DB\conditions\ComplexCondition.cs" />
+    <Compile Include="DB\conditions\ConditionsJoinType.cs" />
+    <Compile Include="DB\conditions\IsNullCondition.cs" />
+    <Compile Include="DB\conditions\MultiValueCondition.cs" />
+    <Compile Include="DB\conditions\NotIsNullCondition.cs" />
+    <Compile Include="DB\conditions\SimpleCondition.cs" />
+    <Compile Include="DB\Diapasone.cs" />
+    <Compile Include="DB\IDBConnection.cs" />
+    <Compile Include="DB\ILock.cs" />
+    <Compile Include="DB\ITableSpec.cs" />
+    <Compile Include="DB\JoinSpec.cs" />
+    <Compile Include="DB\SortSpec.cs" />
     <Compile Include="delegates\Lazy.cs" />
     <Compile Include="delegates\Predicate.cs" />
     <Compile Include="exceptions\CriticalException.cs" />
diff --git a/Core/DB/ColumnOrValue.cs b/Core/DB/ColumnOrValue.cs
new file mode 100644
index 0000000..9893d71
--- /dev/null
+++ b/Core/DB/ColumnOrValue.cs
@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	class ColumnOrValue {
+
+		private bool _isColumn;
+
+		private ColumnSpec _column;
+
+		private string _value;
+
+		private ColumnOrValue() { }
+
+		public static ColumnOrValue createColumn(ColumnSpec column) {
+			return new ColumnOrValue{_isColumn = true, _column = column};
+		}
+
+		public static ColumnOrValue createValue(string value) {
+			return new ColumnOrValue{_isColumn = false, _value = value};
+		}
+
+		public bool isColumn {
+			get {
+				return this._isColumn;
+			}
+		}
+
+		public ColumnSpec column {
+			get {
+				if(!this.isColumn) throw new CriticalException("Not a column");
+				return this._column;
+			}
+		}
+
+		public string value {
+			get {
+				if(this.isColumn) throw new CriticalException("not a value");
+				return this._value;
+			}
+		}
+
+	}
+}
diff --git a/Core/DB/ColumnSpec.cs b/Core/DB/ColumnSpec.cs
new file mode 100644
index 0000000..328c1cc
--- /dev/null
+++ b/Core/DB/ColumnSpec.cs
@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	public class ColumnSpec {
+
+		public readonly ITableSpec table;
+
+		public readonly string name;
+
+		public ColumnSpec(ITableSpec table, string name) {
+			this.table = table;
+			this.name = name;
+		}
+
+	}
+}
diff --git a/Core/DB/Diapasone.cs b/Core/DB/Diapasone.cs
new file mode 100644
index 0000000..b04cf6c
--- /dev/null
+++ b/Core/DB/Diapasone.cs
@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	class Diapasone {
+
+		public readonly int start;
+		public readonly int count;
+		public int total {
+			get;
+			private set;
+		}
+
+		public Diapasone(int start, int count) {
+			this.start = start;
+			this.count = count;
+		}
+
+	}
+}
diff --git a/Core/DB/IDBConnection.cs b/Core/DB/IDBConnection.cs
new file mode 100644
index 0000000..9e844a8
--- /dev/null
+++ b/Core/DB/IDBConnection.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	interface IDBConnection {
+
+		Dictionary<string, string> LoadById(ITableSpec table, int id);
+		Dictionary<string, string>[] LoadByIds(ITableSpec table, int[] ids);
+
+		int[] LoadIdsByConditions(ITableSpec table, conditions.AbstractCondition conditions, Diapasone diapasone, JoinSpec[] joins, SortSpec[] sorts);
+
+		ILock lockTable(ITableSpec table);
+
+		ILock lockRow(ITableSpec table, int id);
+
+		void update(ITableSpec table, int id, Dictionary<string, string> data);
+
+		void delete(ITableSpec table, int id); //do we really need this?
+
+	}
+
+	static class IDBConnectionExtensions {
+
+		public static int[] LoadIdsByConditions(this IDBConnection connection, ITableSpec table, conditions.AbstractCondition conditions, Diapasone diapasone, params JoinSpec[] joins) {
+			return connection.LoadIdsByConditions(table, conditions, diapasone, joins, new SortSpec[] { new SortSpec(table.getIdSpec(), true) });
+		}
+
+	}
+
+}
diff --git a/Core/DB/ILock.cs b/Core/DB/ILock.cs
new file mode 100644
index 0000000..99769a9
--- /dev/null
+++ b/Core/DB/ILock.cs
@@ -0,0 +1,9 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	public interface ILock : IDisposable {
+	}
+}
diff --git a/Core/DB/ITableSpec.cs b/Core/DB/ITableSpec.cs
new file mode 100644
index 0000000..8b4eac3
--- /dev/null
+++ b/Core/DB/ITableSpec.cs
@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	public interface ITableSpec {
+		string name {
+			get;
+		}
+
+		string idName {
+			get;
+		}
+
+	}
+
+	public static class ITableSpecExtensions {
+
+		public static ColumnSpec getIdSpec(this ITableSpec table) {
+			return new ColumnSpec(table, table.idName);
+		}
+
+	}
+
+}
diff --git a/Core/DB/JoinSpec.cs b/Core/DB/JoinSpec.cs
new file mode 100644
index 0000000..80ed097
--- /dev/null
+++ b/Core/DB/JoinSpec.cs
@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	class JoinSpec {
+
+		public readonly ColumnSpec mainColumn;
+
+		public readonly ITableSpec additionalTable;
+
+		public JoinSpec(ColumnSpec mainColumn, ITableSpec additionalTable) {
+			this.mainColumn = mainColumn;
+			this.additionalTable = additionalTable;
+		}
+
+	}
+}
diff --git a/Core/DB/SortSpec.cs b/Core/DB/SortSpec.cs
new file mode 100644
index 0000000..c1379c7
--- /dev/null
+++ b/Core/DB/SortSpec.cs
@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB {
+	class SortSpec {
+
+		public readonly ColumnSpec column;
+	
+		public readonly bool ascending;
+
+		public SortSpec(ColumnSpec column, bool ascending) {
+			this.column = column;
+			this.ascending = ascending;
+		}
+
+	}
+}
diff --git a/Core/DB/conditions/AbstractCondition.cs b/Core/DB/conditions/AbstractCondition.cs
new file mode 100644
index 0000000..5f05ff1
--- /dev/null
+++ b/Core/DB/conditions/AbstractCondition.cs
@@ -0,0 +1,10 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	public abstract class AbstractCondition {
+
+	}
+}
diff --git a/Core/DB/conditions/ComparisonCondition.cs b/Core/DB/conditions/ComparisonCondition.cs
new file mode 100644
index 0000000..5442116
--- /dev/null
+++ b/Core/DB/conditions/ComparisonCondition.cs
@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	class ComparisonCondition : SimpleCondition {
+
+		public readonly ColumnSpec left;
+		public readonly ComparisonType comparison;
+		public readonly ColumnOrValue right;
+
+		public ComparisonCondition(ColumnSpec left, ComparisonType comparison, ColumnSpec right) {
+			this.left = left;
+			this.comparison = comparison;
+			this.right = ColumnOrValue.createColumn(right);
+		}
+
+		public ComparisonCondition(ColumnSpec left, ComparisonType comparison, string right) {
+			this.left = left;
+			this.comparison = comparison;
+			this.right = ColumnOrValue.createValue(right);
+		}
+
+	}
+}
diff --git a/Core/DB/conditions/ComparisonType.cs b/Core/DB/conditions/ComparisonType.cs
new file mode 100644
index 0000000..3ce1397
--- /dev/null
+++ b/Core/DB/conditions/ComparisonType.cs
@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	enum ComparisonType {
+		EQUAL,
+		NOTEQUAL,
+		LESSTHAN,
+		GREATERTHAN,
+		LESSOREQUAL,
+		GREATEROREQUAL,
+	}
+}
diff --git a/Core/DB/conditions/ComplexCondition.cs b/Core/DB/conditions/ComplexCondition.cs
new file mode 100644
index 0000000..077c4ab
--- /dev/null
+++ b/Core/DB/conditions/ComplexCondition.cs
@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	class ComplexCondition : AbstractCondition {
+
+		public readonly ConditionsJoinType type;
+
+		public readonly List<AbstractCondition> innerConditions;
+
+		public ComplexCondition(ConditionsJoinType type, List<AbstractCondition> innerConditions) {
+			this.type = type;
+			this.innerConditions = innerConditions;
+		}
+
+	}
+}
diff --git a/Core/DB/conditions/ConditionsJoinType.cs b/Core/DB/conditions/ConditionsJoinType.cs
new file mode 100644
index 0000000..8514aec
--- /dev/null
+++ b/Core/DB/conditions/ConditionsJoinType.cs
@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	enum ConditionsJoinType {
+		AND,
+		OR,
+	}
+}
diff --git a/Core/DB/conditions/IsNullCondition.cs b/Core/DB/conditions/IsNullCondition.cs
new file mode 100644
index 0000000..c82d8a7
--- /dev/null
+++ b/Core/DB/conditions/IsNullCondition.cs
@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	public class IsNullCondition : SimpleCondition {
+
+		public readonly ColumnSpec column;
+
+		public IsNullCondition(ColumnSpec column) {
+			this.column = column;
+		}
+
+	}
+}
diff --git a/Core/DB/conditions/MultiValueCondition.cs b/Core/DB/conditions/MultiValueCondition.cs
new file mode 100644
index 0000000..492259f
--- /dev/null
+++ b/Core/DB/conditions/MultiValueCondition.cs
@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	class MultiValueCondition : SimpleCondition {
+
+		public readonly ColumnSpec column;
+
+		public readonly bool inclusive;
+
+		public readonly string[] values;
+
+		public MultiValueCondition(ColumnSpec column, string[] values, bool inclusive) {
+			this.column = column;
+			this.values = values;
+			this.inclusive = inclusive;
+		}
+
+		public MultiValueCondition(ColumnSpec column, string[] values) : this(column, values, true) {
+		}
+
+	}
+}
diff --git a/Core/DB/conditions/NotIsNullCondition.cs b/Core/DB/conditions/NotIsNullCondition.cs
new file mode 100644
index 0000000..27f26d0
--- /dev/null
+++ b/Core/DB/conditions/NotIsNullCondition.cs
@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	public class NotIsNullCondition : SimpleCondition {
+
+		public readonly ColumnSpec column;
+
+		public NotIsNullCondition(ColumnSpec column) {
+			this.column = column;
+		}
+
+	}
+}
diff --git a/Core/DB/conditions/SimpleCondition.cs b/Core/DB/conditions/SimpleCondition.cs
new file mode 100644
index 0000000..acadaca
--- /dev/null
+++ b/Core/DB/conditions/SimpleCondition.cs
@@ -0,0 +1,9 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace FLocal.Core.DB.conditions {
+	public abstract class SimpleCondition : AbstractCondition {
+	}
+}