diff --git a/xos/tosca/resources/serviceinstance.py b/xos/tosca/resources/serviceinstance.py
new file mode 100644
index 0000000..7b0babf
--- /dev/null
+++ b/xos/tosca/resources/serviceinstance.py
@@ -0,0 +1,68 @@
+
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from core.models import User, ServiceInstanceLink, Service, ServiceInstance
+
+from xosresource import XOSResource
+
+class XOSServiceInstance(XOSResource):
+    provides = ["tosca.nodes.Tenant", "tosca.nodes.ServiceInstance"]
+    xos_model = ServiceInstance
+    copyin_props = ["service_specific_id"]
+
+    def get_xos_args(self, throw_exception=True):
+        args = super(XOSServiceInstance, self).get_xos_args()
+
+        provider_name = self.get_requirement("tosca.relationships.MemberOfService", throw_exception=throw_exception)
+        if provider_name:
+            args["owner"] = self.get_xos_object(Service, throw_exception=throw_exception, name=provider_name)
+
+        return args
+
+    def get_existing_objs(self):
+        args = self.get_xos_args(throw_exception=False)
+        provider_service = args.get("owner", None)
+        service_specific_id = args.get("service_specific_id", None)
+        if (provider_service) and (service_specific_id):
+            existing_obj = self.get_xos_object(ServiceInstance, owner=provider_service, service_specific_id=service_specific_id, throw_exception=False)
+            if existing_obj:
+                return [ existing_obj ]
+        return []
+
+    def postprocess(self, obj):
+        subscriber_name = self.get_requirement("tosca.relationships.BelongsToSubscriber")
+        if subscriber_name:
+            subscriber = self.get_xos_object(ServiceInstance, throw_exception=True, name=subscriber_name)
+
+            links = ServiceInstanceLink.objects.filter(provider_service_instance = obj,
+                                                       subscriber_service_instance = subscriber)
+            if not links:
+                link = ServiceInstanceLink(provider_service_instance = obj, subscriber_service_instance = subscriber)
+                link.save()
+
+        tenant_name = self.get_requirement("tosca.relationships.BelongsToTenant")
+        if tenant_name:
+            tenant = self.get_xos_object(ServiceInstance, throw_exception=True, name=tenant_name)
+            links = ServiceInstanceLink.objects.filter(provider_service_instance = obj,
+                                                       subscriber_service_instance = tenant)
+            if not links:
+                link = ServiceInstanceLink(provider_service_instance = obj, subscriber_service_instance = tenant)
+                link.save()
+
+
+
+    def can_delete(self, obj):
+        return super(XOSServiceInstance, self).can_delete(obj)