diff --git a/core/luajit/context.cc b/core/luajit/context.cc
index 0313e18..b975ff4 100644
--- a/core/luajit/context.cc
+++ b/core/luajit/context.cc
@@ -41,6 +41,7 @@ void TaskContext::Push(const nf7::Value& v) noexcept {
             v.is<nf7::Value::Real>()   ? "real":
             v.is<nf7::Value::Buffer>() ? "buffer":
             v.is<nf7::Value::Object>() ? "object":
+            v.is<nf7::Value::SharedData>() ? "data":
             "unknown");
         return 1;
       });
diff --git a/iface/common/value.hh b/iface/common/value.hh
index 43bb44e..2fde9c7 100644
--- a/iface/common/value.hh
+++ b/iface/common/value.hh
@@ -147,7 +147,13 @@ class Value final {
     std::shared_ptr<const Pair[]> pairs_;
   };
 
-  using Variant = std::variant<Null, Integer, Real, Buffer, Object>;
+  class Data {
+   public:
+    virtual ~Data() = default;
+  };
+  using SharedData = std::shared_ptr<Data>;
+
+  using Variant = std::variant<Null, Integer, Real, Buffer, Object, SharedData>;
 
  public:
   static Value MakeNull(Null v = {}) noexcept { return v; }
@@ -217,6 +223,14 @@ class Value final {
     return MakeArray(v.begin(), v.end());
   }
 
+  template <typename T, typename... Args>
+  static Value MakeSharedData(Args&&... args)
+  try {
+    return Value {std::make_shared<T>(std::forward<Args>(args)...)};
+  } catch (const std::bad_alloc&) {
+    throw MemoryException {};
+  }
+
  public:
   Value() noexcept : var_(Null {}) { }
   Value(Null v) noexcept : var_(v) { }
@@ -226,6 +240,8 @@ class Value final {
   Value(const Buffer& v) noexcept : var_(v) { }
   Value(Object&& v) noexcept : var_(std::move(v)) { }
   Value(const Object& v) noexcept : var_(v) { }
+  Value(SharedData&& v) noexcept : var_(std::move(v)) { }
+  Value(const SharedData& v) noexcept : var_(v) { }
 
  public:
   Value(const Value&) = default;
@@ -277,6 +293,16 @@ class Value final {
     throw Exception {"value is not a number", location};
   }
 
+  template <typename T>
+  std::shared_ptr<T> data(
+      std::source_location loc = std::source_location::current()) const {
+    static_assert(std::is_base_of_v<Data, T>);
+
+    const auto ret = std::dynamic_pointer_cast<T>(as<SharedData>(loc));
+    return nullptr != ret? ret:
+        throw Exception {"incompatible data type", loc};
+  }
+
  private:
   Variant var_;
 };
diff --git a/iface/common/value_test.cc b/iface/common/value_test.cc
index ef19794..84b728f 100644
--- a/iface/common/value_test.cc
+++ b/iface/common/value_test.cc
@@ -4,6 +4,14 @@
 #include <gtest/gtest.h>
 
 
+namespace {
+
+class CustomData1 : public nf7::Value::Data { };
+class CustomData2 : public nf7::Value::Data { };
+
+}  // namespace
+
+
 TEST(Value, NullAsNull) {
   const auto v = nf7::Value::MakeNull();
   EXPECT_TRUE(v.is<nf7::Value::Null>());
@@ -11,6 +19,7 @@ TEST(Value, NullAsNull) {
   EXPECT_FALSE(v.is<nf7::Value::Real>());
   EXPECT_FALSE(v.is<nf7::Value::Buffer>());
   EXPECT_FALSE(v.is<nf7::Value::Object>());
+  EXPECT_FALSE(v.is<nf7::Value::SharedData>());
 }
 TEST(Value, NullAsInvalid) {
   const auto v = nf7::Value::MakeNull();
@@ -18,6 +27,7 @@ TEST(Value, NullAsInvalid) {
   EXPECT_THROW(v.as<nf7::Value::Real>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Buffer>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Object>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::SharedData>(), nf7::Exception);
 }
 TEST(Value, NullEqual) {
   EXPECT_EQ(nf7::Value::MakeNull(), nf7::Value::MakeNull());
@@ -27,6 +37,7 @@ TEST(Value, NullNotEqual) {
   EXPECT_NE(nf7::Value::MakeNull(), nf7::Value::MakeReal(0));
   EXPECT_NE(nf7::Value::MakeNull(), nf7::Value::MakeBuffer<uint8_t>({}));
   EXPECT_NE(nf7::Value::MakeNull(), nf7::Value::MakeObject({}));
+  EXPECT_NE(nf7::Value::MakeNull(), nf7::Value::MakeSharedData<CustomData1>());
 }
 
 TEST(Value, IntegerAsInteger) {
@@ -37,6 +48,7 @@ TEST(Value, IntegerAsInteger) {
   EXPECT_FALSE(v.is<nf7::Value::Real>());
   EXPECT_FALSE(v.is<nf7::Value::Buffer>());
   EXPECT_FALSE(v.is<nf7::Value::Object>());
+  EXPECT_FALSE(v.is<nf7::Value::SharedData>());
 
   EXPECT_EQ(v.as<nf7::Value::Integer>(), nf7::Value::Integer {777});
 }
@@ -46,6 +58,7 @@ TEST(Value, IntegerAsInvalid) {
   EXPECT_THROW(v.as<nf7::Value::Real>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Buffer>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Object>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::SharedData>(), nf7::Exception);
 }
 TEST(Value, IntegerAsValidNum) {
   const nf7::Value v = nf7::Value::MakeInteger(777);
@@ -66,6 +79,7 @@ TEST(Value, IntegerNotEqual) {
   EXPECT_NE(nf7::Value::MakeInteger(666), nf7::Value::MakeReal(0));
   EXPECT_NE(nf7::Value::MakeInteger(666), nf7::Value::MakeBuffer<uint8_t>({}));
   EXPECT_NE(nf7::Value::MakeInteger(666), nf7::Value::MakeObject({}));
+  EXPECT_NE(nf7::Value::MakeInteger(666), nf7::Value::MakeSharedData<CustomData1>());
 }
 
 TEST(Value, RealAsReal) {
@@ -76,6 +90,7 @@ TEST(Value, RealAsReal) {
   EXPECT_TRUE(v.is<nf7::Value::Real>());
   EXPECT_FALSE(v.is<nf7::Value::Buffer>());
   EXPECT_FALSE(v.is<nf7::Value::Object>());
+  EXPECT_FALSE(v.is<nf7::Value::SharedData>());
 
   EXPECT_EQ(v.as<nf7::Value::Real>(), nf7::Value::Real {777});
 }
@@ -85,6 +100,7 @@ TEST(Value, RealAsInvalid) {
   EXPECT_THROW(v.as<nf7::Value::Integer>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Buffer>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Object>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::SharedData>(), nf7::Exception);
 }
 TEST(Value, RealAsValidNum) {
   const auto v = nf7::Value::MakeReal(777);
@@ -105,6 +121,7 @@ TEST(Value, RealNotEqual) {
   EXPECT_NE(nf7::Value::MakeReal(1), nf7::Value::MakeInteger(1));
   EXPECT_NE(nf7::Value::MakeReal(1), nf7::Value::MakeBuffer<uint8_t>({}));
   EXPECT_NE(nf7::Value::MakeReal(1), nf7::Value::MakeObject({}));
+  EXPECT_NE(nf7::Value::MakeReal(1), nf7::Value::MakeSharedData<CustomData1>());
 }
 
 TEST(Value, BufferAsBuffer) {
@@ -114,6 +131,7 @@ TEST(Value, BufferAsBuffer) {
   EXPECT_FALSE(v.is<nf7::Value::Real>());
   EXPECT_TRUE(v.is<nf7::Value::Buffer>());
   EXPECT_FALSE(v.is<nf7::Value::Object>());
+  EXPECT_FALSE(v.is<nf7::Value::SharedData>());
 }
 TEST(Value, BufferAsInvalid) {
   const auto v = nf7::Value::MakeBuffer<uint8_t>({});
@@ -121,6 +139,7 @@ TEST(Value, BufferAsInvalid) {
   EXPECT_THROW(v.as<nf7::Value::Integer>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Real>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Object>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::SharedData>(), nf7::Exception);
 }
 TEST(Value, BufferEqual) {
   const auto v = nf7::Value::MakeBuffer<uint8_t>({});
@@ -133,6 +152,7 @@ TEST(Value, BufferNotEqual) {
   EXPECT_NE(nf7::Value::MakeBuffer<uint8_t>({}),
             nf7::Value::MakeBuffer<uint8_t>({}));
   EXPECT_NE(nf7::Value::MakeBuffer<uint8_t>({}), nf7::Value::MakeObject({}));
+  EXPECT_NE(nf7::Value::MakeBuffer<uint8_t>({}), nf7::Value::MakeSharedData<CustomData1>());
 }
 
 TEST(Value, ObjectAsObject) {
@@ -142,6 +162,7 @@ TEST(Value, ObjectAsObject) {
   EXPECT_FALSE(v.is<nf7::Value::Real>());
   EXPECT_FALSE(v.is<nf7::Value::Buffer>());
   EXPECT_TRUE(v.is<nf7::Value::Object>());
+  EXPECT_FALSE(v.is<nf7::Value::SharedData>());
 }
 TEST(Value, ObjectAsInvalid) {
   const auto v = nf7::Value::MakeObject({});
@@ -149,6 +170,7 @@ TEST(Value, ObjectAsInvalid) {
   EXPECT_THROW(v.as<nf7::Value::Integer>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Real>(), nf7::Exception);
   EXPECT_THROW(v.as<nf7::Value::Buffer>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::SharedData>(), nf7::Exception);
 }
 TEST(Value, ObjectEqual) {
   const auto v = nf7::Value::MakeObject({});
@@ -160,6 +182,53 @@ TEST(Value, ObjectNotEqual) {
   EXPECT_NE(nf7::Value::MakeObject({}), nf7::Value::MakeReal(0));
   EXPECT_NE(nf7::Value::MakeObject({}), nf7::Value::MakeBuffer<uint8_t>({}));
   EXPECT_NE(nf7::Value::MakeObject({}), nf7::Value::MakeObject({}));
+  EXPECT_NE(nf7::Value::MakeObject({}), nf7::Value::MakeSharedData<CustomData1>());
+}
+
+TEST(Value, DataAsCompatibleData) {
+  const auto v = nf7::Value::MakeSharedData<CustomData1>();
+  EXPECT_FALSE(v.is<nf7::Value::Null>());
+  EXPECT_FALSE(v.is<nf7::Value::Integer>());
+  EXPECT_FALSE(v.is<nf7::Value::Real>());
+  EXPECT_FALSE(v.is<nf7::Value::Buffer>());
+  EXPECT_FALSE(v.is<nf7::Value::Object>());
+  EXPECT_TRUE(v.is<nf7::Value::SharedData>());
+
+  EXPECT_NE(v.data<CustomData1>(), nullptr);
+}
+TEST(Value, DataAsIncompatibleData) {
+  const auto v = nf7::Value::MakeSharedData<CustomData1>();
+  EXPECT_THROW(v.data<CustomData2>(), nf7::Exception);
+}
+TEST(Value, DataAsInvalid) {
+  const auto v = nf7::Value::MakeSharedData<CustomData1>();
+  EXPECT_THROW(v.as<nf7::Value::Null>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Integer>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Real>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Buffer>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Object>(), nf7::Exception);
+}
+TEST(Value, DataAsIncompatibleType) {
+  const auto v = nf7::Value::MakeSharedData<CustomData1>();
+  EXPECT_THROW(v.as<nf7::Value::Null>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Integer>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Real>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Buffer>(), nf7::Exception);
+  EXPECT_THROW(v.as<nf7::Value::Object>(), nf7::Exception);
+}
+TEST(Value, DataEqual) {
+  const auto v = nf7::Value::MakeSharedData<CustomData1>();
+  EXPECT_EQ(v, v);
+}
+TEST(Value, DataNotEqual) {
+  const auto v = nf7::Value::MakeSharedData<CustomData1>();
+  EXPECT_NE(v, nf7::Value::MakeNull());
+  EXPECT_NE(v, nf7::Value::MakeInteger(0));
+  EXPECT_NE(v, nf7::Value::MakeReal(0));
+  EXPECT_NE(v, nf7::Value::MakeBuffer<uint8_t>({}));
+  EXPECT_NE(v, nf7::Value::MakeObject({}));
+  EXPECT_NE(v, nf7::Value::MakeSharedData<CustomData1>());
+  EXPECT_NE(v, nf7::Value::MakeSharedData<CustomData2>());
 }
 
 TEST(ValueBuffer, Make) {