diff --git a/contrib/xos/common.proto b/contrib/xos/common.proto
new file mode 100644
index 0000000..5f82f7d
--- /dev/null
+++ b/contrib/xos/common.proto
@@ -0,0 +1,39 @@
+syntax = "proto3";
+
+package xos;
+
+message ID {
+    int32 id = 1;
+}
+
+message QueryElement {
+    enum QueryOperator {
+        EQUAL = 0;
+        GREATER_THAN = 1;
+        LESS_THAN = 2;
+        GREATER_THAN_OR_EQUAL = 3;
+        LESS_THAN_OR_EQUAL = 4;
+        IEXACT = 5;
+    }
+    QueryOperator operator = 1;
+    bool invert = 2;
+    string name = 3;
+    oneof value {
+        string sValue = 4;
+        int32 iValue = 5;
+    }
+};
+
+message Query {
+    enum QueryKind {
+        DEFAULT=0;
+        ALL=1;
+        SYNCHRONIZER_DIRTY_OBJECTS = 2;
+        SYNCHRONIZER_DELETED_OBJECTS = 3;
+        SYNCHRONIZER_DIRTY_POLICIES = 4;
+        SYNCHRONIZER_DELETED_POLICIES = 5;
+    }
+    QueryKind kind = 1;
+    repeated QueryElement elements = 2;
+};
+