diff --git a/bigchaindb/core.py b/bigchaindb/core.py
index 7e395614..805a6d16 100644
--- a/bigchaindb/core.py
+++ b/bigchaindb/core.py
@@ -6,11 +6,12 @@ from time import time
 from itertools import compress
 from bigchaindb_common import crypto, exceptions
 from bigchaindb_common.util import gen_timestamp, serialize
-from bigchaindb_common.transaction import TransactionLink
+from bigchaindb_common.transaction import TransactionLink, Metadata
 
 import rethinkdb as r
 
 import bigchaindb
+
 from bigchaindb.db.utils import Connection
 from bigchaindb import config_utils, util
 from bigchaindb.consensus import BaseConsensusRules
@@ -326,32 +327,52 @@ class Bigchain(object):
         else:
             return None
 
-    def get_tx_by_payload_uuid(self, payload_uuid):
-        """Retrieves transactions related to a digital asset.
+    def get_tx_by_metadata_id(self, metadata_id):
+        """Retrieves transactions related to a metadata.
 
-        When creating a transaction one of the optional arguments is the `payload`. The payload is a generic
-        dict that contains information about the digital asset.
+        When creating a transaction one of the optional arguments is the `metadata`. The metadata is a generic
+        dict that contains extra information that can be appended to the transaction.
 
-        To make it easy to query BigchainDB for that digital asset we create a UUID for the payload and
-        store it with the transaction. This makes it easy for developers to keep track of their digital
-        assets in bigchain.
+        To make it easy to query the bigchain for that particular metadata we create a UUID for the metadata and
+        store it with the transaction.
 
         Args:
-            payload_uuid (str): the UUID for this particular payload.
+            metadata_id (str): the id for this particular metadata.
 
         Returns:
-            A list of transactions containing that payload. If no transaction exists with that payload it
+            A list of transactions containing that metadata. If no transaction exists with that metadata it
             returns an empty list `[]`
         """
-        cursor = self.connection.run(
-                r.table('bigchain', read_mode=self.read_mode)
-                .get_all(payload_uuid, index='payload_uuid')
-                .concat_map(lambda block: block['block']['transactions'])
-                .filter(lambda transaction: transaction['transaction']['data']['uuid'] == payload_uuid))
+        cursor = r.table('bigchain', read_mode=self.read_mode) \
+            .get_all(metadata_id, index='metadata_id') \
+            .concat_map(lambda block: block['block']['transactions']) \
+            .filter(lambda transaction: transaction['transaction']['metadata']['id'] == metadata_id) \
+            .run(self.conn)
 
         transactions = list(cursor)
         return [Transaction.from_dict(tx) for tx in transactions]
 
+    def get_txs_by_asset_id(self, asset_id):
+        """Retrieves transactions related to a particular asset.
+
+        A digital asset in bigchaindb is identified by an uuid. This allows us to query all the transactions
+        related to a particular digital asset, knowing the id.
+
+        Args:
+            asset_id (str): the id for this particular metadata.
+
+        Returns:
+            A list of transactions containing related to the asset. If no transaction exists for that asset it
+            returns an empty list `[]`
+        """
+        cursor = self.connection.run(
+            r.table('bigchain', read_mode=self.read_mode)
+             .get_all(asset_id, index='asset_id')
+             .concat_map(lambda block: block['block']['transactions'])
+             .filter(lambda transaction: transaction['transaction']['asset']['id'] == asset_id))
+
+        return [Transaction.from_dict(tx) for tx in cursor]
+
     def get_spent(self, txid, cid):
         """Check if a `txid` was already used as an input.
 
@@ -536,8 +557,9 @@ class Bigchain(object):
     def prepare_genesis_block(self):
         """Prepare a genesis block."""
 
-        payload = {'message': 'Hello World from the BigchainDB'}
-        transaction = Transaction.create([self.me], [self.me], payload=payload)
+        metadata = {'message': 'Hello World from the BigchainDB'}
+        transaction = Transaction.create([self.me], [self.me],
+                                         metadata=metadata)
 
         # NOTE: The transaction model doesn't expose an API to generate a
         #       GENESIS transaction, as this is literally the only usage.
diff --git a/bigchaindb/db/utils.py b/bigchaindb/db/utils.py
index 0ed74471..0009b2c3 100644
--- a/bigchaindb/db/utils.py
+++ b/bigchaindb/db/utils.py
@@ -105,9 +105,14 @@ def create_bigchain_secondary_index(conn, dbname):
         .run(conn)
     # secondary index for payload data by UUID
     r.db(dbname).table('bigchain')\
-        .index_create('payload_uuid',
-                      r.row['block']['transactions']['transaction']['data']['uuid'], multi=True)\
+        .index_create('metadata_id',
+                      r.row['block']['transactions']['transaction']['metadata']['id'], multi=True)\
         .run(conn)
+    # secondary index for asset uuid
+    r.db(dbname).table('bigchain')\
+                .index_create('asset_id',
+                              r.row['block']['transactions']['transaction']['asset']['id'], multi=True)\
+                .run(conn)
 
     # wait for rethinkdb to finish creating secondary indexes
     r.db(dbname).table('bigchain').index_wait().run(conn)
diff --git a/bigchaindb/models.py b/bigchaindb/models.py
index e31d1a5d..342d6443 100644
--- a/bigchaindb/models.py
+++ b/bigchaindb/models.py
@@ -2,11 +2,42 @@ from bigchaindb_common.crypto import hash_data, VerifyingKey, SigningKey
 from bigchaindb_common.exceptions import (InvalidHash, InvalidSignature,
                                           OperationError, DoubleSpend,
                                           TransactionDoesNotExist,
-                                          FulfillmentNotInValidBlock)
-from bigchaindb_common.transaction import Transaction
+                                          FulfillmentNotInValidBlock,
+                                          AssetIdMismatch)
+from bigchaindb_common.transaction import Transaction, Asset
 from bigchaindb_common.util import gen_timestamp, serialize
 
 
+class Asset(Asset):
+    @staticmethod
+    def get_asset_id(transactions):
+        """Get the asset id from a list of transaction ids.
+
+        This is useful when we want to check if the multiple inputs of a transaction
+        are related to the same asset id.
+
+        Args:
+            transactions (list): list of transaction usually inputs that should have a matching asset_id
+
+        Returns:
+            str: uuid of the asset.
+
+        Raises:
+            AssetIdMismatch: If the inputs are related to different assets.
+        """
+
+        if not isinstance(transactions, list):
+            transactions = [transactions]
+
+        # create a set of asset_ids
+        asset_ids = {tx.asset.data_id for tx in transactions}
+
+        # check that all the transasctions have the same asset_id
+        if len(asset_ids) > 1:
+            raise AssetIdMismatch("All inputs of a transaction need to have the same asset id.")
+        return asset_ids.pop()
+
+
 class Transaction(Transaction):
     def validate(self, bigchain):
         """Validate a transaction.
@@ -36,13 +67,18 @@ class Transaction(Transaction):
         inputs_defined = all([ffill.tx_input for ffill in self.fulfillments])
 
         if self.operation in (Transaction.CREATE, Transaction.GENESIS):
+            # validate inputs
             if inputs_defined:
                 raise ValueError('A CREATE operation has no inputs')
+            # validate asset
+            self.asset._validate_asset()
         elif self.operation == Transaction.TRANSFER:
             if not inputs_defined:
                 raise ValueError('Only `CREATE` transactions can have null '
                                  'inputs')
-
+            # check inputs
+            # store the inputs so that we can check if the asset ids match
+            input_txs = []
             for ffill in self.fulfillments:
                 input_txid = ffill.tx_input.txid
                 input_cid = ffill.tx_input.cid
@@ -64,6 +100,12 @@ class Transaction(Transaction):
                                       .format(input_txid))
 
                 input_conditions.append(input_tx.conditions[input_cid])
+                input_txs.append(input_tx)
+
+            # validate asset id
+            asset_id = Asset.get_asset_id(input_txs)
+            if asset_id != self.asset.data_id:
+                raise AssetIdMismatch('The asset id of the input does not match the asset id of the transaction')
         else:
             allowed_operations = ', '.join(Transaction.ALLOWED_OPERATIONS)
             raise TypeError('`operation`: `{}` must be either {}.'
diff --git a/bigchaindb/util.py b/bigchaindb/util.py
index 3e84b4ba..007d8f7e 100644
--- a/bigchaindb/util.py
+++ b/bigchaindb/util.py
@@ -1,20 +1,10 @@
-import time
 import contextlib
-from copy import deepcopy
 import threading
 import queue
 import multiprocessing as mp
-import uuid
 
-import rapidjson
-
-from bigchaindb_common import crypto, exceptions
+from bigchaindb_common import crypto
 from bigchaindb_common.util import serialize
-import cryptoconditions as cc
-from cryptoconditions.exceptions import ParsingError
-
-import bigchaindb
-from bigchaindb.models import Transaction
 
 
 class ProcessGroup(object):
diff --git a/setup.py b/setup.py
index b003abbe..16258344 100644
--- a/setup.py
+++ b/setup.py
@@ -103,7 +103,7 @@ setup(
         'requests~=2.9',
         'gunicorn~=19.0',
         'multipipes~=0.1.0',
-        'bigchaindb-common>=0.0.2',
+        'bigchaindb-common>=0.0.4',
     ],
     setup_requires=['pytest-runner'],
     tests_require=tests_require,
diff --git a/tests/assets/__init__.py b/tests/assets/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/assets/conftest.py b/tests/assets/conftest.py
new file mode 100644
index 00000000..1a3a77e2
--- /dev/null
+++ b/tests/assets/conftest.py
@@ -0,0 +1,19 @@
+import pytest
+from ..db import conftest
+
+
+@pytest.fixture(autouse=True)
+def restore_config(request, node_config):
+    from bigchaindb import config_utils
+    config_utils.set_config(node_config)
+
+
+@pytest.fixture(scope='module', autouse=True)
+def setup_database(request, node_config):
+    conftest.setup_database(request, node_config)
+
+
+@pytest.fixture(scope='function', autouse=True)
+def cleanup_tables(request, node_config):
+    conftest.cleanup_tables(request, node_config)
+
diff --git a/tests/assets/test_digital_assets.py b/tests/assets/test_digital_assets.py
new file mode 100644
index 00000000..64da4c11
--- /dev/null
+++ b/tests/assets/test_digital_assets.py
@@ -0,0 +1,163 @@
+import pytest
+from ..db.conftest import inputs
+
+
+@pytest.mark.usefixtures('inputs')
+def test_asset_transfer(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+
+    tx_input = b.get_owned_ids(user_vk).pop()
+    tx_create = b.get_transaction(tx_input.txid)
+
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_vk],
+                                       tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert tx_transfer_signed.asset.data_id == tx_create.asset.data_id
+
+
+def test_validate_bad_asset_creation(b, user_vk):
+    from bigchaindb.models import Transaction
+
+    # `divisible` needs to be a boolean
+    tx = Transaction.create([b.me], [user_vk])
+    tx.asset.divisible = 1
+    tx_signed = tx.sign([b.me_private])
+    with pytest.raises(TypeError):
+        tx_signed.validate(b)
+
+    # `refillable` needs to be a boolean
+    tx = Transaction.create([b.me], [user_vk])
+    tx.asset.refillable = 1
+    tx_signed = tx.sign([b.me_private])
+    with pytest.raises(TypeError):
+        b.validate_transaction(tx_signed)
+
+    # `updatable` needs to be a boolean
+    tx = Transaction.create([b.me], [user_vk])
+    tx.asset.updatable = 1
+    tx_signed = tx.sign([b.me_private])
+    with pytest.raises(TypeError):
+        b.validate_transaction(tx_signed)
+
+    # `data` needs to be a dictionary
+    tx = Transaction.create([b.me], [user_vk])
+    tx.asset.data = 'a'
+    tx_signed = tx.sign([b.me_private])
+    with pytest.raises(TypeError):
+        b.validate_transaction(tx_signed)
+
+    # TODO: Check where to test for the amount
+    """
+    tx = b.create_transaction(b.me, user_vk, None, 'CREATE')
+    tx['transaction']['conditions'][0]['amount'] = 'a'
+    tx['id'] = get_hash_data(tx['transaction'])
+    tx_signed = b.sign_transaction(tx, b.me_private)
+    with pytest.raises(TypeError):
+        b.validate_transaction(tx_signed)
+
+    tx = b.create_transaction(b.me, user_vk, None, 'CREATE')
+    tx['transaction']['conditions'][0]['amount'] = 2
+    tx['transaction']['asset'].update({'divisible': False})
+    tx['id'] = get_hash_data(tx['transaction'])
+    tx_signed = b.sign_transaction(tx, b.me_private)
+    with pytest.raises(AmountError):
+        b.validate_transaction(tx_signed)
+
+    tx = b.create_transaction(b.me, user_vk, None, 'CREATE')
+    tx['transaction']['conditions'][0]['amount'] = 0
+    tx['id'] = get_hash_data(tx['transaction'])
+    tx_signed = b.sign_transaction(tx, b.me_private)
+    with pytest.raises(AmountError):
+        b.validate_transaction(tx_signed)
+    """
+
+
+@pytest.mark.usefixtures('inputs')
+def test_validate_transfer_asset_id_mismatch(b, user_vk, user_sk):
+    from bigchaindb_common.exceptions import AssetIdMismatch
+    from bigchaindb.models import Transaction
+
+    tx_create = b.get_owned_ids(user_vk).pop()
+    tx_create = b.get_transaction(tx_create.txid)
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_vk],
+                                       tx_create.asset)
+    tx_transfer.asset.data_id = 'aaa'
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+    with pytest.raises(AssetIdMismatch):
+        tx_transfer_signed.validate(b)
+
+
+def test_get_asset_id_create_transaction(b, user_vk):
+    from bigchaindb.models import Transaction, Asset
+
+    tx_create = Transaction.create([b.me], [user_vk])
+    asset_id = Asset.get_asset_id(tx_create)
+
+    assert asset_id == tx_create.asset.data_id
+
+
+@pytest.mark.usefixtures('inputs')
+def test_get_asset_id_transfer_transaction(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction, Asset
+
+    tx_create = b.get_owned_ids(user_vk).pop()
+    tx_create = b.get_transaction(tx_create.txid)
+    # create a transfer transaction
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_vk],
+                                       tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+    # create a block
+    block = b.create_block([tx_transfer_signed])
+    b.write_block(block, durability='hard')
+    # vote the block valid
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+    asset_id = Asset.get_asset_id(tx_transfer)
+
+    assert asset_id == tx_transfer.asset.data_id
+
+
+def test_asset_id_mismatch(b, user_vk):
+    from bigchaindb.models import Transaction, Asset
+    from bigchaindb_common.exceptions import AssetIdMismatch
+
+    tx1 = Transaction.create([b.me], [user_vk])
+    tx2 = Transaction.create([b.me], [user_vk])
+
+    with pytest.raises(AssetIdMismatch):
+        Asset.get_asset_id([tx1, tx2])
+
+
+@pytest.mark.usefixtures('inputs')
+def test_get_txs_by_asset_id(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+
+    tx_create = b.get_owned_ids(user_vk).pop()
+    tx_create = b.get_transaction(tx_create.txid)
+    asset_id = tx_create.asset.data_id
+    txs = b.get_txs_by_asset_id(asset_id)
+
+    assert len(txs) == 1
+    assert txs[0].id == tx_create.id
+    assert txs[0].asset.data_id == asset_id
+
+    # create a transfer transaction
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_vk],
+                                       tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+    # create the block
+    block = b.create_block([tx_transfer_signed])
+    b.write_block(block, durability='hard')
+    # vote the block valid
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    txs = b.get_txs_by_asset_id(asset_id)
+
+    assert len(txs) == 2
+    assert tx_create.id in [t.id for t in txs]
+    assert tx_transfer.id in [t.id for t in txs]
+    assert asset_id == txs[0].asset.data_id
+    assert asset_id == txs[1].asset.data_id
diff --git a/tests/conftest.py b/tests/conftest.py
index 73bd025f..58178b7f 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -84,5 +84,5 @@ def signed_create_tx(b, create_tx):
 def signed_transfer_tx(signed_create_tx, user_vk, user_sk):
     from bigchaindb.models import Transaction
     inputs = signed_create_tx.to_inputs()
-    tx = Transaction.transfer(inputs, [user_vk])
+    tx = Transaction.transfer(inputs, [user_vk], signed_create_tx.asset)
     return tx.sign([user_sk])
diff --git a/tests/db/conftest.py b/tests/db/conftest.py
index 3cd9ae49..ec4afc9b 100644
--- a/tests/db/conftest.py
+++ b/tests/db/conftest.py
@@ -51,8 +51,8 @@ def setup_database(request, node_config):
     r.db(db_name).table('backlog').index_create('transaction_timestamp', r.row['transaction']['timestamp']).run()
     # to query by payload uuid
     r.db(db_name).table('bigchain').index_create(
-        'payload_uuid',
-        r.row['block']['transactions']['transaction']['data']['uuid'],
+        'metadata_id',
+        r.row['block']['transactions']['transaction']['metadata']['id'],
         multi=True,
     ).run()
     # compound index to read transactions from the backlog per assignee
@@ -62,6 +62,11 @@ def setup_database(request, node_config):
     # compound index to order votes by block id and node
     r.db(db_name).table('votes').index_create('block_and_voter',
                                               [r.row['vote']['voting_for_block'], r.row['node_pubkey']]).run()
+    # secondary index for asset uuid
+    r.db(db_name).table('bigchain')\
+                .index_create('asset_id',
+                              r.row['block']['transactions']['transaction']['asset']['id'], multi=True)\
+                .run()
     # order transactions by id
     r.db(db_name).table('bigchain').index_create('transaction_id', r.row['block']['transactions']['id'],
                                                  multi=True).run()
@@ -114,8 +119,7 @@ def inputs(user_vk):
     prev_block_id = g.id
     for block in range(4):
         transactions = [
-            Transaction.create(
-                [b.me], [user_vk], payload={'i': i}).sign([b.me_private])
+            Transaction.create([b.me], [user_vk]).sign([b.me_private])
             for i in range(10)
         ]
         block = b.create_block(transactions)
diff --git a/tests/db/test_bigchain_api.py b/tests/db/test_bigchain_api.py
index 7b57049c..d056cbfe 100644
--- a/tests/db/test_bigchain_api.py
+++ b/tests/db/test_bigchain_api.py
@@ -88,6 +88,11 @@ class TestBigchainApi(object):
 
         assert b.has_previous_vote(block.id, block.voters) is True
 
+
+    def test_get_transactions_for_metadata_mismatch(self, b):
+        matches = b.get_tx_by_metadata_id('missing')
+        assert not matches
+
     def test_get_spent_with_double_spend(self, b, monkeypatch):
         from bigchaindb_common.exceptions import DoubleSpend
         from bigchaindb.models import Transaction
@@ -102,13 +107,13 @@ class TestBigchainApi(object):
         b.write_block(block1, durability='hard')
 
         monkeypatch.setattr('time.time', lambda: 2)
-        transfer_tx = Transaction.transfer(tx.to_inputs(), [b.me])
+        transfer_tx = Transaction.transfer(tx.to_inputs(), [b.me], tx.asset)
         transfer_tx = transfer_tx.sign([b.me_private])
         block2 = b.create_block([transfer_tx])
         b.write_block(block2, durability='hard')
 
         monkeypatch.setattr('time.time', lambda: 3)
-        transfer_tx2 = Transaction.transfer(tx.to_inputs(), [b.me])
+        transfer_tx2 = Transaction.transfer(tx.to_inputs(), [b.me], tx.asset)
         transfer_tx2 = transfer_tx2.sign([b.me_private])
         block3 = b.create_block([transfer_tx2])
         b.write_block(block3, durability='hard')
@@ -173,24 +178,24 @@ class TestBigchainApi(object):
         vote = b.vote(block2.id, b.get_last_voted_block().id, True)
         b.write_vote(vote)
 
-        assert b.get_transaction(tx1.id) == None
+        assert b.get_transaction(tx1.id) is None
         assert b.get_transaction(tx2.id) == tx2
 
-    def test_get_transactions_for_payload(self, b, user_vk):
+    def test_get_transactions_for_metadata(self, b, user_vk):
         from bigchaindb.models import Transaction
 
-        payload = {'msg': 'Hello BigchainDB!'}
-        tx = Transaction.create([b.me], [user_vk], payload=payload)
+        metadata = {'msg': 'Hello BigchainDB!'}
+        tx = Transaction.create([b.me], [user_vk], metadata=metadata)
 
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
 
-        matches = b.get_tx_by_payload_uuid(tx.data.payload_id)
+        matches = b.get_tx_by_payload_uuid(tx.metadata.data_id)
         assert len(matches) == 1
         assert matches[0].id == tx.id
 
-    def test_get_transactions_for_payload_mismatch(self, b, user_vk):
-        matches = b.get_tx_by_payload_uuid('missing')
+    def test_get_transactions_for_metadata(self, b, user_vk):
+        matches = b.get_tx_by_metadata_id('missing')
         assert not matches
 
     @pytest.mark.usefixtures('inputs')
@@ -200,7 +205,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_vk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_vk])
+        tx = Transaction.transfer(inputs, [user_vk], input_tx.asset)
         tx = tx.sign([user_sk])
         response = b.write_transaction(tx)
 
@@ -218,7 +223,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_vk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_vk])
+        tx = Transaction.transfer(inputs, [user_vk], input_tx.asset)
         tx = tx.sign([user_sk])
         b.write_transaction(tx)
 
@@ -238,7 +243,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_vk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_vk])
+        tx = Transaction.transfer(inputs, [user_vk], input_tx.asset)
         tx = tx.sign([user_sk])
         b.write_transaction(tx)
 
@@ -480,7 +485,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_vk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_vk])
+        tx = Transaction.transfer(inputs, [user_vk], input_tx.asset)
         tx = tx.sign([user_sk])
         b.write_transaction(tx)
 
@@ -505,7 +510,7 @@ class TestBigchainApi(object):
             input_tx = b.get_owned_ids(user_vk).pop()
             input_tx = b.get_transaction(input_tx.txid)
             inputs = input_tx.to_inputs()
-            tx = Transaction.transfer(inputs, [user_vk])
+            tx = Transaction.transfer(inputs, [user_vk], input_tx.asset)
             tx = tx.sign([user_sk])
             b.write_transaction(tx)
 
@@ -516,6 +521,25 @@ class TestBigchainApi(object):
             assert response['assignee'] in b.nodes_except_me
 
 
+    @pytest.mark.usefixtures('inputs')
+    def test_non_create_input_not_found(self, b, user_vk):
+        from cryptoconditions import Ed25519Fulfillment
+        from bigchaindb_common.exceptions import TransactionDoesNotExist
+        from bigchaindb_common.transaction import (Fulfillment, Asset,
+                                                   TransactionLink)
+        from bigchaindb.models import Transaction
+        from bigchaindb import Bigchain
+
+        # Create a fulfillment for a non existing transaction
+        fulfillment = Fulfillment(Ed25519Fulfillment(public_key=user_vk),
+                                  [user_vk],
+                                  TransactionLink('somethingsomething', 0))
+        tx = Transaction.transfer([fulfillment], [user_vk], Asset())
+
+        with pytest.raises(TransactionDoesNotExist) as excinfo:
+            tx.validate(Bigchain())
+
+
 class TestTransactionValidation(object):
     def test_create_operation_with_inputs(self, b, user_vk, create_tx):
         from bigchaindb_common.transaction import TransactionLink
@@ -550,9 +574,11 @@ class TestTransactionValidation(object):
         from bigchaindb.models import Transaction
 
         input_tx = b.get_owned_ids(user_vk).pop()
+        input_transaction = b.get_transaction(input_tx.txid)
         sk, vk = generate_key_pair()
         tx = Transaction.create([vk], [user_vk])
         tx.operation = 'TRANSFER'
+        tx.asset = input_transaction.asset
         tx.fulfillments[0].tx_input = input_tx
 
         with pytest.raises(InvalidSignature):
@@ -594,7 +620,7 @@ class TestTransactionValidation(object):
         input_tx = b.get_owned_ids(user_vk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        transfer_tx = Transaction.transfer(inputs, [user_vk])
+        transfer_tx = Transaction.transfer(inputs, [user_vk], input_tx.asset)
         transfer_tx = transfer_tx.sign([user_sk])
 
         assert transfer_tx == b.validate_transaction(transfer_tx)
@@ -618,7 +644,7 @@ class TestTransactionValidation(object):
         inputs = input_tx.to_inputs()
 
         # create a transaction that's valid but not in a voted valid block
-        transfer_tx = Transaction.transfer(inputs, [user_vk])
+        transfer_tx = Transaction.transfer(inputs, [user_vk], input_tx.asset)
         transfer_tx = transfer_tx.sign([user_sk])
 
         assert transfer_tx == b.validate_transaction(transfer_tx)
@@ -628,7 +654,8 @@ class TestTransactionValidation(object):
         b.write_block(block, durability='hard')
 
         # create transaction with the undecided input
-        tx_invalid = Transaction.transfer(transfer_tx.to_inputs(), [user_vk])
+        tx_invalid = Transaction.transfer(transfer_tx.to_inputs(), [user_vk],
+                                         transfer_tx.asset)
         tx_invalid = tx_invalid.sign([user_sk])
 
         with pytest.raises(FulfillmentNotInValidBlock):
@@ -726,7 +753,7 @@ class TestMultipleInputs(object):
         tx_link = b.get_owned_ids(user_vk).pop()
         input_tx = b.get_transaction(tx_link.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user2_vk])
+        tx = Transaction.transfer(inputs, [user2_vk], input_tx.asset)
         tx = tx.sign([user_sk])
 
         # validate transaction
@@ -734,6 +761,9 @@ class TestMultipleInputs(object):
         assert len(tx.fulfillments) == 1
         assert len(tx.conditions) == 1
 
+    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
+                                'same asset. Remove this after implementing ',
+                                'multiple assets'))
     @pytest.mark.usefixtures('inputs')
     def test_transfer_single_owners_multiple_inputs(self, b, user_sk, user_vk):
         from bigchaindb_common import crypto
@@ -752,6 +782,9 @@ class TestMultipleInputs(object):
         assert len(tx.fulfillments) == len(inputs)
         assert len(tx.conditions) == len(inputs)
 
+    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
+                                'same asset. Remove this after implementing ',
+                                'multiple assets'))
     @pytest.mark.usefixtures('inputs')
     def test_transfer_single_owners_single_input_from_multiple_outputs(self, b,
                                                                        user_sk,
@@ -779,7 +812,7 @@ class TestMultipleInputs(object):
 
         # get inputs from user2
         owned_inputs = b.get_owned_ids(user2_vk)
-        assert len(owned_inputs) == len(inputs) 
+        assert len(owned_inputs) == len(inputs)
 
         # create a transaction with a single input from a multiple output transaction
         tx_link = owned_inputs.pop()
@@ -803,14 +836,17 @@ class TestMultipleInputs(object):
 
         owned_inputs = b.get_owned_ids(user_vk)
         tx_link = owned_inputs.pop()
-        inputs = b.get_transaction(tx_link.txid).to_inputs()
-        tx = Transaction.transfer(inputs, [[user2_vk, user3_vk]])
+        input_tx = b.get_transaction(tx_link.txid)
+        tx = Transaction.transfer(input_tx.to_inputs(), [[user2_vk, user3_vk]], input_tx.asset)
         tx = tx.sign([user_sk])
 
         assert b.is_valid_transaction(tx) == tx
         assert len(tx.fulfillments) == 1
         assert len(tx.conditions) == 1
 
+    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
+                                'same asset. Remove this after implementing ',
+                                'multiple assets'))
     @pytest.mark.usefixtures('inputs')
     def test_single_owner_before_multiple_owners_after_multiple_inputs(self, b,
                                                                        user_sk,
@@ -865,7 +901,7 @@ class TestMultipleInputs(object):
         input_tx = b.get_transaction(owned_input.txid)
         inputs = input_tx.to_inputs()
 
-        transfer_tx = Transaction.transfer(inputs, [user3_vk])
+        transfer_tx = Transaction.transfer(inputs, [user3_vk], input_tx.asset)
         transfer_tx = transfer_tx.sign([user_sk, user2_sk])
 
         # validate transaction
@@ -873,6 +909,9 @@ class TestMultipleInputs(object):
         assert len(transfer_tx.fulfillments) == 1
         assert len(transfer_tx.conditions) == 1
 
+    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
+                                'same asset. Remove this after implementing ',
+                                'multiple assets'))
     @pytest.mark.usefixtures('inputs_shared')
     def test_multiple_owners_before_single_owner_after_multiple_inputs(self, b,
                                           user_sk, user_vk, user2_vk, user2_sk):
@@ -915,15 +954,18 @@ class TestMultipleInputs(object):
 
         # get input
         tx_link = b.get_owned_ids(user_vk).pop()
-        tx_input = b.get_transaction(tx_link.txid).to_inputs()
+        tx_input = b.get_transaction(tx_link.txid)
 
-        tx = Transaction.transfer(tx_input, [[user3_vk, user4_vk]])
+        tx = Transaction.transfer(tx_input.to_inputs(), [[user3_vk, user4_vk]], tx_input.asset)
         tx = tx.sign([user_sk, user2_sk])
 
         assert b.is_valid_transaction(tx) == tx
         assert len(tx.fulfillments) == 1
         assert len(tx.conditions) == 1
 
+    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
+                                'same asset. Remove this after implementing ',
+                                'multiple assets'))
     @pytest.mark.usefixtures('inputs_shared')
     def test_multiple_owners_before_multiple_owners_after_multiple_inputs(self, b,
                                                                 user_sk, user_vk,
@@ -944,7 +986,7 @@ class TestMultipleInputs(object):
 
         assert b.is_valid_transaction(tx) == tx
         assert len(tx.fulfillments) == len(inputs)
-        assert len(tx.conditions) == len(inputs) 
+        assert len(tx.conditions) == len(inputs)
 
     def test_get_owned_ids_single_tx_single_output(self, b, user_sk, user_vk):
         from bigchaindb_common import crypto
@@ -963,7 +1005,7 @@ class TestMultipleInputs(object):
         assert owned_inputs_user1 == [TransactionLink(tx.id, 0)]
         assert owned_inputs_user2 == []
 
-        tx = Transaction.transfer(tx.to_inputs(), [user2_vk])
+        tx = Transaction.transfer(tx.to_inputs(), [user2_vk], tx.asset)
         tx = tx.sign([user_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -999,7 +1041,7 @@ class TestMultipleInputs(object):
 
         # NOTE: The transaction itself is valid, still will mark the block
         #       as invalid to mock the behavior.
-        tx_invalid = Transaction.transfer(tx.to_inputs(), [user2_vk])
+        tx_invalid = Transaction.transfer(tx.to_inputs(), [user2_vk], tx.asset)
         tx_invalid = tx_invalid.sign([user_sk])
         block = b.create_block([tx_invalid])
         b.write_block(block, durability='hard')
@@ -1015,6 +1057,9 @@ class TestMultipleInputs(object):
         assert owned_inputs_user1 == [TransactionLink(tx.id, 0)]
         assert owned_inputs_user2 == []
 
+    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
+                                'same asset. Remove this after implementing ',
+                                'multiple assets'))
     def test_get_owned_ids_single_tx_multiple_outputs(self, b, user_sk,
                                                       user_vk):
         import random
@@ -1074,7 +1119,7 @@ class TestMultipleInputs(object):
         assert owned_inputs_user1 == owned_inputs_user2
         assert owned_inputs_user1 == expected_owned_inputs_user1
 
-        tx = Transaction.transfer(tx.to_inputs(), [user3_vk])
+        tx = Transaction.transfer(tx.to_inputs(), [user3_vk], tx.asset)
         tx = tx.sign([user_sk, user2_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1104,7 +1149,7 @@ class TestMultipleInputs(object):
         assert spent_inputs_user1 is None
 
         # create a transaction and block
-        tx = Transaction.transfer(tx.to_inputs(), [user2_vk])
+        tx = Transaction.transfer(tx.to_inputs(), [user2_vk], tx.asset)
         tx = tx.sign([user_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1139,7 +1184,7 @@ class TestMultipleInputs(object):
         assert spent_inputs_user1 is None
 
         # create a transaction and block
-        tx = Transaction.transfer(tx.to_inputs(), [user2_vk])
+        tx = Transaction.transfer(tx.to_inputs(), [user2_vk], tx.asset)
         tx = tx.sign([user_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1154,6 +1199,9 @@ class TestMultipleInputs(object):
         # Now there should be no spents (the block is invalid)
         assert spent_inputs_user1 is None
 
+    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
+                                'same asset. Remove this after implementing ',
+                                'multiple assets'))
     def test_get_spent_single_tx_multiple_outputs(self, b, user_sk, user_vk):
         import random
         from bigchaindb_common import crypto
@@ -1218,7 +1266,7 @@ class TestMultipleInputs(object):
             assert b.get_spent(input_tx.txid, input_tx.cid) is None
 
         # create a transaction
-        tx = Transaction.transfer(transactions[0].to_inputs(), [user3_vk])
+        tx = Transaction.transfer(transactions[0].to_inputs(), [user3_vk], transactions[0].asset)
         tx = tx.sign([user_sk, user2_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
diff --git a/tests/db/test_utils.py b/tests/db/test_utils.py
index f22bcd04..56f09ac5 100644
--- a/tests/db/test_utils.py
+++ b/tests/db/test_utils.py
@@ -79,7 +79,7 @@ def test_create_bigchain_secondary_index():
     assert r.db(dbname).table('bigchain').index_list().contains(
         'transaction_id').run(conn) is True
     assert r.db(dbname).table('bigchain').index_list().contains(
-        'payload_uuid').run(conn) is True
+        'metadata_id').run(conn) is True
 
 
 def test_create_backlog_table():
diff --git a/tests/pipelines/test_stale_monitor.py b/tests/pipelines/test_stale_monitor.py
index 511b0492..5045344b 100644
--- a/tests/pipelines/test_stale_monitor.py
+++ b/tests/pipelines/test_stale_monitor.py
@@ -83,10 +83,7 @@ def test_full_pipeline(user_vk):
     original_txc = []
 
     for i in range(100):
-        # FIXME Notice the payload. This is only to make sure that the
-        # transactions hashes are unique. See
-        # https://github.com/bigchaindb/bigchaindb-common/issues/21
-        tx = Transaction.create([b.me], [user_vk], payload={'i': i})
+        tx = Transaction.create([b.me], [user_vk])
         tx = tx.sign([b.me_private])
         original_txc.append(tx.to_dict())
 
diff --git a/tests/pipelines/test_vote.py b/tests/pipelines/test_vote.py
index 3ac431b7..09811b0d 100644
--- a/tests/pipelines/test_vote.py
+++ b/tests/pipelines/test_vote.py
@@ -274,7 +274,7 @@ def test_valid_block_voting_with_transfer_transactions(monkeypatch, b):
 
     # create a `TRANSFER` transaction
     test_user2_priv, test_user2_pub = crypto.generate_key_pair()
-    tx2 = Transaction.transfer(tx.to_inputs(), [test_user2_pub])
+    tx2 = Transaction.transfer(tx.to_inputs(), [test_user2_pub], tx.asset)
     tx2 = tx2.sign([test_user_priv])
 
     monkeypatch.setattr('time.time', lambda: 2)
diff --git a/tests/web/test_basic_views.py b/tests/web/test_basic_views.py
index 829374cd..b941011a 100644
--- a/tests/web/test_basic_views.py
+++ b/tests/web/test_basic_views.py
@@ -77,7 +77,7 @@ def test_post_transfer_transaction_endpoint(b, client, user_vk, user_sk):
 
     input_valid = b.get_owned_ids(user_vk).pop()
     create_tx = b.get_transaction(input_valid.txid)
-    transfer_tx = Transaction.transfer(create_tx.to_inputs(), [user_pub])
+    transfer_tx = Transaction.transfer(create_tx.to_inputs(), [user_pub], create_tx.asset)
     transfer_tx = transfer_tx.sign([user_sk])
 
     res = client.post(TX_ENDPOINT, data=json.dumps(transfer_tx.to_dict()))
@@ -94,7 +94,7 @@ def test_post_invalid_transfer_transaction_returns_400(b, client, user_vk, user_
 
     input_valid = b.get_owned_ids(user_vk).pop()
     create_tx = b.get_transaction(input_valid.txid)
-    transfer_tx = Transaction.transfer(create_tx.to_inputs(), [user_pub])
+    transfer_tx = Transaction.transfer(create_tx.to_inputs(), [user_pub], create_tx.asset)
 
     res = client.post(TX_ENDPOINT, data=json.dumps(transfer_tx.to_dict()))
     assert res.status_code == 400