diff --git a/lib/fog/compute/xen_server/models/blob.rb b/lib/fog/compute/xen_server/models/blob.rb
index f4d7518..4bbd305 100644
--- a/lib/fog/compute/xen_server/models/blob.rb
+++ b/lib/fog/compute/xen_server/models/blob.rb
@@ -7,6 +7,7 @@ class Blob < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=blob
 
           provider_class :blob
+          collection_name :blobs
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/bond.rb b/lib/fog/compute/xen_server/models/bond.rb
index be5b675..ac288d1 100644
--- a/lib/fog/compute/xen_server/models/bond.rb
+++ b/lib/fog/compute/xen_server/models/bond.rb
@@ -7,6 +7,7 @@ class Bond < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=Bond
 
           provider_class :Bond
+          collection_name :bonds
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/console.rb b/lib/fog/compute/xen_server/models/console.rb
index 2e92547..55882e1 100644
--- a/lib/fog/compute/xen_server/models/console.rb
+++ b/lib/fog/compute/xen_server/models/console.rb
@@ -7,6 +7,7 @@ class Console < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=console
 
           provider_class :console
+          collection_name :consoles
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/crash_dump.rb b/lib/fog/compute/xen_server/models/crash_dump.rb
index 13d60be..9aee184 100644
--- a/lib/fog/compute/xen_server/models/crash_dump.rb
+++ b/lib/fog/compute/xen_server/models/crash_dump.rb
@@ -7,6 +7,7 @@ class CrashDump < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=crashdump
 
           provider_class :crashdump
+          collection_name :crash_dumps
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/dr_task.rb b/lib/fog/compute/xen_server/models/dr_task.rb
index d81292e..b99b63c 100644
--- a/lib/fog/compute/xen_server/models/dr_task.rb
+++ b/lib/fog/compute/xen_server/models/dr_task.rb
@@ -7,6 +7,7 @@ class DrTask < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=DR_task
 
           provider_class :DR_task
+          collection_name :dr_tasks
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/gpu_group.rb b/lib/fog/compute/xen_server/models/gpu_group.rb
index a317973..97d859f 100644
--- a/lib/fog/compute/xen_server/models/gpu_group.rb
+++ b/lib/fog/compute/xen_server/models/gpu_group.rb
@@ -7,6 +7,7 @@ class GpuGroup < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=GPU_group
 
           provider_class :GPU_group
+          collection_name :gpu_groups
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/guest_metrics.rb b/lib/fog/compute/xen_server/models/guest_metrics.rb
index 6d82928..fabc5ca 100644
--- a/lib/fog/compute/xen_server/models/guest_metrics.rb
+++ b/lib/fog/compute/xen_server/models/guest_metrics.rb
@@ -7,6 +7,7 @@ class GuestMetrics < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VM_guest_metrics
 
           provider_class :VM_guest_metrics
+          collection_name :guests_metrics
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/host.rb b/lib/fog/compute/xen_server/models/host.rb
index 5a205ec..f9c202c 100644
--- a/lib/fog/compute/xen_server/models/host.rb
+++ b/lib/fog/compute/xen_server/models/host.rb
@@ -7,6 +7,7 @@ class Host < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=host
 
           provider_class :host
+          collection_name :hosts
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/host_cpu.rb b/lib/fog/compute/xen_server/models/host_cpu.rb
index bb3cc75..52acbe6 100644
--- a/lib/fog/compute/xen_server/models/host_cpu.rb
+++ b/lib/fog/compute/xen_server/models/host_cpu.rb
@@ -7,6 +7,7 @@ class HostCpu < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=host_cpu
 
           provider_class :host_cpu
+          collection_name :host_cpus
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/host_crash_dump.rb b/lib/fog/compute/xen_server/models/host_crash_dump.rb
index 5f68158..fdbba7a 100644
--- a/lib/fog/compute/xen_server/models/host_crash_dump.rb
+++ b/lib/fog/compute/xen_server/models/host_crash_dump.rb
@@ -7,6 +7,7 @@ class HostCrashDump < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=host_crashdump
 
           provider_class :host_crashdump
+          collection_name :host_crash_dumps
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/host_metrics.rb b/lib/fog/compute/xen_server/models/host_metrics.rb
index d34af21..ba62270 100644
--- a/lib/fog/compute/xen_server/models/host_metrics.rb
+++ b/lib/fog/compute/xen_server/models/host_metrics.rb
@@ -7,6 +7,7 @@ class HostMetrics < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=host_metrics
 
           provider_class :host_metrics
+          collection_name :hosts_metrics
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/host_patch.rb b/lib/fog/compute/xen_server/models/host_patch.rb
index b9addba..4fb3b47 100644
--- a/lib/fog/compute/xen_server/models/host_patch.rb
+++ b/lib/fog/compute/xen_server/models/host_patch.rb
@@ -7,6 +7,7 @@ class HostPatch < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=host_patch
 
           provider_class :host_patch
+          collection_name :host_patchs
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/network.rb b/lib/fog/compute/xen_server/models/network.rb
index f85067c..e44cdf6 100644
--- a/lib/fog/compute/xen_server/models/network.rb
+++ b/lib/fog/compute/xen_server/models/network.rb
@@ -7,6 +7,7 @@ class Network < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=network
 
           provider_class :network
+          collection_name :networks
 
           identity :reference
 
@@ -25,10 +26,12 @@ class Network < Fog::Model
           has_many :pifs,  :pifs,         :aliases => :PIFs
           has_many :vifs,  :vifs,         :aliases => :VIFs
 
+          require_before_save :name
+
           def save
-            requires :name
+            require_creation_attributes
             ref = service.create_network name, attributes
-            merge_attributes service.networks.get(ref).attributes
+            merge_attributes collection.get(ref).attributes
             true
           end
         end
diff --git a/lib/fog/compute/xen_server/models/pbd.rb b/lib/fog/compute/xen_server/models/pbd.rb
index fd6e35b..2f606dc 100644
--- a/lib/fog/compute/xen_server/models/pbd.rb
+++ b/lib/fog/compute/xen_server/models/pbd.rb
@@ -7,6 +7,7 @@ class Pbd < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=PBD
 
           provider_class :PBD
+          collection_name :pbds
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/pci.rb b/lib/fog/compute/xen_server/models/pci.rb
index ef79b0b..1b8885b 100644
--- a/lib/fog/compute/xen_server/models/pci.rb
+++ b/lib/fog/compute/xen_server/models/pci.rb
@@ -7,6 +7,7 @@ class Pci < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=PCI
 
           provider_class :PCI
+          collection_name :pcis
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/pgpu.rb b/lib/fog/compute/xen_server/models/pgpu.rb
index 0037398..1d45100 100644
--- a/lib/fog/compute/xen_server/models/pgpu.rb
+++ b/lib/fog/compute/xen_server/models/pgpu.rb
@@ -7,6 +7,7 @@ class Pgpu < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=PGPU
 
           provider_class :PGPU
+          collection_name :pgpus
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/pif.rb b/lib/fog/compute/xen_server/models/pif.rb
index dd4ee75..d252b2e 100644
--- a/lib/fog/compute/xen_server/models/pif.rb
+++ b/lib/fog/compute/xen_server/models/pif.rb
@@ -7,6 +7,7 @@ class Pif < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=PIF
 
           provider_class :PIF
+          collection_name :pifs
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/pif_metrics.rb b/lib/fog/compute/xen_server/models/pif_metrics.rb
index cf91260..eaf2bb0 100644
--- a/lib/fog/compute/xen_server/models/pif_metrics.rb
+++ b/lib/fog/compute/xen_server/models/pif_metrics.rb
@@ -7,6 +7,7 @@ class PifMetrics < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=PIF_metrics
 
           provider_class :PIF_metrics
+          collection_name :pifs_metrics
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/pool.rb b/lib/fog/compute/xen_server/models/pool.rb
index 0051be6..3d3f9dd 100644
--- a/lib/fog/compute/xen_server/models/pool.rb
+++ b/lib/fog/compute/xen_server/models/pool.rb
@@ -7,6 +7,7 @@ class Pool < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=pool
 
           provider_class :pool
+          collection_name :pools
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/pool_patch.rb b/lib/fog/compute/xen_server/models/pool_patch.rb
index cb3c79a..21dad45 100644
--- a/lib/fog/compute/xen_server/models/pool_patch.rb
+++ b/lib/fog/compute/xen_server/models/pool_patch.rb
@@ -7,6 +7,7 @@ class PoolPatch < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=pool_patch
 
           provider_class :pool_patch
+          collection_name :pool_patchs
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/role.rb b/lib/fog/compute/xen_server/models/role.rb
index 46788a4..14f5687 100644
--- a/lib/fog/compute/xen_server/models/role.rb
+++ b/lib/fog/compute/xen_server/models/role.rb
@@ -7,6 +7,7 @@ class Role < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=role
 
           provider_class :role
+          collection_name :roles
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/server.rb b/lib/fog/compute/xen_server/models/server.rb
index d1e6239..1a71de6 100644
--- a/lib/fog/compute/xen_server/models/server.rb
+++ b/lib/fog/compute/xen_server/models/server.rb
@@ -9,6 +9,7 @@ class Server < Fog::Compute::Server
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VM
 
           provider_class :VM
+          collection_name :servers
 
           identity :reference
 
@@ -94,6 +95,8 @@ class Server < Fog::Compute::Server
           has_many  :vifs,              :vifs,                    :aliases => :VIFs
           has_many  :vtpms,             :vtpms,                   :aliases => :VTPMs
 
+          require_before_save :name
+
           def tools_installed?
             !guest_metrics.nil?
           end
@@ -117,7 +120,7 @@ def halted?
           end
 
           def save(params = {})
-            requires :name
+            require_creation_attributes
             nets = params.fetch(:networks, [])
             auto_start = params.fetch(:auto_start, true)
             if template_name
@@ -125,7 +128,7 @@ def save(params = {})
             else
               ref = service.create_server_raw(attributes)
             end
-            merge_attributes service.servers.get(ref).attributes
+            merge_attributes collection.get(ref).attributes
             true
           end
 
diff --git a/lib/fog/compute/xen_server/models/server_appliance.rb b/lib/fog/compute/xen_server/models/server_appliance.rb
index 6f90dfb..03133fe 100644
--- a/lib/fog/compute/xen_server/models/server_appliance.rb
+++ b/lib/fog/compute/xen_server/models/server_appliance.rb
@@ -7,6 +7,7 @@ class ServerAppliance < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VM_appliance
 
           provider_class :VM_appliance
+          collection_name :server_appliances
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/server_metrics.rb b/lib/fog/compute/xen_server/models/server_metrics.rb
index 5fa6b6a..3e309d4 100644
--- a/lib/fog/compute/xen_server/models/server_metrics.rb
+++ b/lib/fog/compute/xen_server/models/server_metrics.rb
@@ -7,6 +7,7 @@ class ServerMetrics < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VM_metrics
 
           provider_class :VM_metrics
+          collection_name :servers_metrics
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/storage_manager.rb b/lib/fog/compute/xen_server/models/storage_manager.rb
index 01262f8..da7ee76 100644
--- a/lib/fog/compute/xen_server/models/storage_manager.rb
+++ b/lib/fog/compute/xen_server/models/storage_manager.rb
@@ -7,6 +7,7 @@ class StorageManager < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=SM
 
           provider_class :SM
+          collection_name :storage_managers
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/storage_repository.rb b/lib/fog/compute/xen_server/models/storage_repository.rb
index 8198ccf..1f26198 100644
--- a/lib/fog/compute/xen_server/models/storage_repository.rb
+++ b/lib/fog/compute/xen_server/models/storage_repository.rb
@@ -7,6 +7,7 @@ class StorageRepository < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=SR
 
           provider_class :SR
+          collection_name :storage_repositories
 
           identity :reference
 
@@ -31,11 +32,13 @@ class StorageRepository < Fog::Model
           has_many  :pbds,  :pbds,         :aliases => :PBDs
           has_many  :vdis,  :vdis,         :aliases => :VDIs
 
+          require_before_save :name, :type
+
           def save(host, device_config = {})
-            requires :name, :type
+            require_creation_attributes
             ref = service.create_sr(host, name, type, description, device_config, physical_size, content_type,
                                     shared || false, sm_config)
-            merge_attributes service.storage_repositories.get(ref).attributes
+            merge_attributes collection.get(ref).attributes
             true
           end
         end
diff --git a/lib/fog/compute/xen_server/models/tunnel.rb b/lib/fog/compute/xen_server/models/tunnel.rb
index ade4c19..d7edbc0 100644
--- a/lib/fog/compute/xen_server/models/tunnel.rb
+++ b/lib/fog/compute/xen_server/models/tunnel.rb
@@ -7,6 +7,7 @@ class Tunnel < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=tunnel
 
           provider_class :tunnel
+          collection_name :tunnels
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/vbd.rb b/lib/fog/compute/xen_server/models/vbd.rb
index b18f9a4..ffd6fee 100644
--- a/lib/fog/compute/xen_server/models/vbd.rb
+++ b/lib/fog/compute/xen_server/models/vbd.rb
@@ -7,6 +7,7 @@ class Vbd < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VBD
 
           provider_class :VBD
+          collection_name :vbds
 
           identity :reference
 
@@ -34,12 +35,14 @@ class Vbd < Fog::Model
           has_one   :vdi,       :vdis,             :aliases => :VDI
           has_one   :vm,        :servers,          :aliases => :VM
 
+          require_before_save :vdi, :server
+
           alias_method :server, :vm
 
           def save
-            requires :vdi, :server
+            require_creation_attributes
             ref = service.create_vbd(server, vdi, attributes)
-            merge_attributes(service.vbds.get(ref).attributes)
+            merge_attributes collection.get(ref).attributes
             true
           end
         end
diff --git a/lib/fog/compute/xen_server/models/vbd_metrics.rb b/lib/fog/compute/xen_server/models/vbd_metrics.rb
index dc69658..0c99dc4 100644
--- a/lib/fog/compute/xen_server/models/vbd_metrics.rb
+++ b/lib/fog/compute/xen_server/models/vbd_metrics.rb
@@ -7,6 +7,7 @@ class VbdMetrics < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VBD_metrics
 
           provider_class :VBD_metrics
+          collection_name :vbds_metrics
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/vdi.rb b/lib/fog/compute/xen_server/models/vdi.rb
index c40e925..03d0db5 100644
--- a/lib/fog/compute/xen_server/models/vdi.rb
+++ b/lib/fog/compute/xen_server/models/vdi.rb
@@ -7,6 +7,7 @@ class Vdi < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VDI
 
           provider_class :VDI
+          collection_name :vdis
 
           identity :reference
 
@@ -42,6 +43,8 @@ class Vdi < Fog::Model
           has_one   :sr,           :storage_repositories,      :aliases => :SR
           has_many  :vbds,         :vbds,                      :aliases => :VBDs
 
+          require_before_save :name, :storage_repository
+
           alias_method :storage_repository, :sr
 
           #
@@ -57,9 +60,9 @@ def initialize(attributes = {})
           end
 
           def save
-            requires :name, :storage_repository
+            require_creation_attributes
             ref = service.create_vdi(attributes)
-            merge_attributes service.vdis.get(ref).attributes
+            merge_attributes collection.get(ref).attributes
             true
           end
         end
diff --git a/lib/fog/compute/xen_server/models/vif.rb b/lib/fog/compute/xen_server/models/vif.rb
index 0725dfa..8f211ac 100644
--- a/lib/fog/compute/xen_server/models/vif.rb
+++ b/lib/fog/compute/xen_server/models/vif.rb
@@ -7,6 +7,7 @@ class Vif < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VIF
 
           provider_class :VIF
+          collection_name :vifs
 
           identity :reference
 
@@ -33,12 +34,14 @@ class Vif < Fog::Model
           has_one   :network,   :networks
           has_one   :vm,        :servers,          :aliases => :VM
 
+          require_before_save :server, :network
+
           alias_method :server, :vm
 
           def save
-            requires :server, :network
+            require_creation_attributes
             ref = service.create_vif(server, network)
-            merge_attributes service.vifs.get(ref).attributes
+            merge_attributes collection.get(ref).attributes
             true
           end
         end
diff --git a/lib/fog/compute/xen_server/models/vif_metrics.rb b/lib/fog/compute/xen_server/models/vif_metrics.rb
index 42ed18c..829e4e6 100644
--- a/lib/fog/compute/xen_server/models/vif_metrics.rb
+++ b/lib/fog/compute/xen_server/models/vif_metrics.rb
@@ -7,6 +7,7 @@ class VifMetrics < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VIF_metrics
 
           provider_class :VIF_metrics
+          collection_name :vifs_metrics
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/vlan.rb b/lib/fog/compute/xen_server/models/vlan.rb
index ca42f80..c74e460 100644
--- a/lib/fog/compute/xen_server/models/vlan.rb
+++ b/lib/fog/compute/xen_server/models/vlan.rb
@@ -7,6 +7,7 @@ class Vlan < Fog::Model
           # @see http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VLAN
 
           provider_class :VLAN
+          collection_name :vlans
 
           identity :reference
 
@@ -17,10 +18,12 @@ class Vlan < Fog::Model
           has_one   :tagged_pif,   :pifs,   :aliases => :tagged_PIF
           has_one   :untagged_pif, :pifs,   :aliases => :untagged_PIF
 
+          require_before_save :tag
+
           def save(pif, network)
-            requires :tag
+            require_creation_attributes
             ref = service.create_vlan(pif, tag, network)
-            merge_attributes service.vlans.get(ref).attributes
+            merge_attributes collection.get(ref).attributes
             true
           end
         end
diff --git a/lib/fog/compute/xen_server/models/vmpp.rb b/lib/fog/compute/xen_server/models/vmpp.rb
index a24f06c..d80e47a 100644
--- a/lib/fog/compute/xen_server/models/vmpp.rb
+++ b/lib/fog/compute/xen_server/models/vmpp.rb
@@ -7,6 +7,7 @@ class Vmpp < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VMPP
 
           provider_class :VMPP
+          collection_name :vmpps
 
           identity :reference
 
diff --git a/lib/fog/compute/xen_server/models/vtpm.rb b/lib/fog/compute/xen_server/models/vtpm.rb
index f0bc5f3..b172024 100644
--- a/lib/fog/compute/xen_server/models/vtpm.rb
+++ b/lib/fog/compute/xen_server/models/vtpm.rb
@@ -7,6 +7,7 @@ class Vtpm < Fog::Model
           # http://docs.vmd.citrix.com/XenServer/6.2.0/1.0/en_gb/api/?c=VTPM
 
           provider_class :VTPM
+          collection_name :vtpms
 
           identity :reference
 
diff --git a/lib/fog/model.rb b/lib/fog/model.rb
index 556f435..e912cb8 100644
--- a/lib/fog/model.rb
+++ b/lib/fog/model.rb
@@ -11,6 +11,15 @@ def provider_class
       self.class.provider_class
     end
 
+    def self.collection_name(collection_name = nil)
+      return @collection_name if collection_name.nil?
+      @collection_name = collection_name
+    end
+
+    def collection
+      service.send(self.class.collection_name)
+    end
+
     def self.has_one(association, collection_name, options = {})
       options[:aliases] = Array(options[:aliases])
       options[:aliases] << association.to_sym
@@ -33,6 +42,15 @@ def self.has_many(associations, collection_name, options = {})
       end
     end
 
+    def self.require_before_save(*args)
+      return @require_before_save || [] if args.empty?
+      @require_before_save = args
+    end
+
+    def require_creation_attributes
+      requires self.class.instance_variable_get(@require_before_save)
+    end
+
     def set_attribute(name, *val)
       service.set_attribute(provider_class, reference, name, *val)
     end
diff --git a/spec/fog/compute/xen_server/models/blob_spec.rb b/spec/fog/compute/xen_server/models/blob_spec.rb
index d053026..c74c641 100644
--- a/spec/fog/compute/xen_server/models/blob_spec.rb
+++ b/spec/fog/compute/xen_server/models/blob_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     blob_class.provider_class.must_equal('blob')
   end
 
+  it 'should have a collection name' do
+    blob_class.collection_name.must_equal(:blobs)
+  end
+
   it 'should have an unique id' do
     blob_class.read_identity.must_equal(:reference)
   end
@@ -37,4 +41,8 @@ def self.read_identity
   it "shouldn't have default values" do
     blob_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    blob_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/bond_spec.rb b/spec/fog/compute/xen_server/models/bond_spec.rb
index 9f8cb73..6af6cb8 100644
--- a/spec/fog/compute/xen_server/models/bond_spec.rb
+++ b/spec/fog/compute/xen_server/models/bond_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     bond_class.provider_class.must_equal('Bond')
   end
 
+  it 'should have a collection name' do
+    bond_class.collection_name.must_equal(:bonds)
+  end
+
   it 'should have an unique id' do
     bond_class.read_identity.must_equal(:reference)
   end
@@ -39,4 +43,8 @@ def self.read_identity
   it "shouldn't have default values" do
     bond_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    bond_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/console_spec.rb b/spec/fog/compute/xen_server/models/console_spec.rb
index 09620aa..9aa2c36 100644
--- a/spec/fog/compute/xen_server/models/console_spec.rb
+++ b/spec/fog/compute/xen_server/models/console_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     console_class.provider_class.must_equal('console')
   end
 
+  it 'should have a collection name' do
+    console_class.collection_name.must_equal(:consoles)
+  end
+
   it 'should have an unique id' do
     console_class.read_identity.must_equal(:reference)
   end
@@ -35,4 +39,8 @@ def self.read_identity
   it "shouldn't have default values" do
     console_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    console_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/crash_dump_spec.rb b/spec/fog/compute/xen_server/models/crash_dump_spec.rb
index 47470cd..6d2f527 100644
--- a/spec/fog/compute/xen_server/models/crash_dump_spec.rb
+++ b/spec/fog/compute/xen_server/models/crash_dump_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     crash_dump_class.provider_class.must_equal('crashdump')
   end
 
+  it 'should have a collection name' do
+    crash_dump_class.collection_name.must_equal(:crash_dumps)
+  end
+
   it 'should have an unique id' do
     crash_dump_class.read_identity.must_equal(:reference)
   end
@@ -36,4 +40,8 @@ def self.read_identity
   it "shouldn't have default values" do
     crash_dump_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    crash_dump_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/dr_task_spec.rb b/spec/fog/compute/xen_server/models/dr_task_spec.rb
index abdab1a..0c3778d 100644
--- a/spec/fog/compute/xen_server/models/dr_task_spec.rb
+++ b/spec/fog/compute/xen_server/models/dr_task_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     dr_task_class.provider_class.must_equal('DR_task')
   end
 
+  it 'should have a collection name' do
+    dr_task_class.collection_name.must_equal(:dr_tasks)
+  end
+
   it 'should have an unique id' do
     dr_task_class.read_identity.must_equal(:reference)
   end
@@ -32,4 +36,8 @@ def self.read_identity
   it "shouldn't have default values" do
     dr_task_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    dr_task_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/gpu_group_spec.rb b/spec/fog/compute/xen_server/models/gpu_group_spec.rb
index ddcead2..a191a0a 100644
--- a/spec/fog/compute/xen_server/models/gpu_group_spec.rb
+++ b/spec/fog/compute/xen_server/models/gpu_group_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     gpu_group_class.provider_class.must_equal('GPU_group')
   end
 
+  it 'should have a collection name' do
+    gpu_group_class.collection_name.must_equal(:gpu_groups)
+  end
+
   it 'should have an unique id' do
     gpu_group_class.read_identity.must_equal(:reference)
   end
@@ -42,4 +46,8 @@ def self.read_identity
   it "shouldn't have default values" do
     gpu_group_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    gpu_group_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/guest_metrics_spec.rb b/spec/fog/compute/xen_server/models/guest_metrics_spec.rb
index 172976f..2717ffd 100644
--- a/spec/fog/compute/xen_server/models/guest_metrics_spec.rb
+++ b/spec/fog/compute/xen_server/models/guest_metrics_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     guest_metrics_class.provider_class.must_equal('VM_guest_metrics')
   end
 
+  it 'should have a collection name' do
+    guest_metrics_class.collection_name.must_equal(:guests_metrics)
+  end
+
   it 'should have an unique id' do
     guest_metrics_class.read_identity.must_equal(:reference)
   end
@@ -41,4 +45,8 @@ def self.read_identity
   it "shouldn't have default values" do
     guest_metrics_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    guest_metrics_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/host_cpu_spec.rb b/spec/fog/compute/xen_server/models/host_cpu_spec.rb
index b4b4fee..8f681e7 100644
--- a/spec/fog/compute/xen_server/models/host_cpu_spec.rb
+++ b/spec/fog/compute/xen_server/models/host_cpu_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     host_cpu_class.provider_class.must_equal('host_cpu')
   end
 
+  it 'should have a collection name' do
+    host_cpu_class.collection_name.must_equal(:host_cpus)
+  end
+
   it 'should have an unique id' do
     host_cpu_class.read_identity.must_equal(:reference)
   end
@@ -43,4 +47,8 @@ def self.read_identity
   it "shouldn't have default values" do
     host_cpu_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    host_cpu_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/host_crash_dump_spec.rb b/spec/fog/compute/xen_server/models/host_crash_dump_spec.rb
index 0a932e6..40fdea1 100644
--- a/spec/fog/compute/xen_server/models/host_crash_dump_spec.rb
+++ b/spec/fog/compute/xen_server/models/host_crash_dump_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     host_crash_dump_class.provider_class.must_equal('host_crashdump')
   end
 
+  it 'should have a collection name' do
+    host_crash_dump_class.collection_name.must_equal(:host_crash_dumps)
+  end
+
   it 'should have an unique id' do
     host_crash_dump_class.read_identity.must_equal(:reference)
   end
@@ -34,4 +38,8 @@ def self.read_identity
   it "shouldn't have default values" do
     host_crash_dump_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    host_crash_dump_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/host_metrics_spec.rb b/spec/fog/compute/xen_server/models/host_metrics_spec.rb
index 3ba0765..68d742f 100644
--- a/spec/fog/compute/xen_server/models/host_metrics_spec.rb
+++ b/spec/fog/compute/xen_server/models/host_metrics_spec.rb
@@ -16,6 +16,10 @@ def self.read_identity
     host_metrics_class.provider_class.must_equal('host_metrics')
   end
 
+  it 'should have a collection name' do
+    host_metrics_class.collection_name.must_equal(:hosts_metrics)
+  end
+
   it 'should have an unique id' do
     host_metrics_class.read_identity.must_equal(:reference)
   end
@@ -38,6 +42,10 @@ def self.read_identity
     host_metrics_class.default_values.must_equal({})
   end
 
+  it "shouldn't require attributes before save" do
+    host_metrics_class.require_before_save.must_equal([])
+  end
+
   describe '#last_updated' do
     before :each do
       host_metrics.last_updated = XMLRPC::DateTime.new(2000, 7, 8, 10, 20, 34)
diff --git a/spec/fog/compute/xen_server/models/host_patch_spec.rb b/spec/fog/compute/xen_server/models/host_patch_spec.rb
index d6f73f1..8e6be5f 100644
--- a/spec/fog/compute/xen_server/models/host_patch_spec.rb
+++ b/spec/fog/compute/xen_server/models/host_patch_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     host_patch_class.provider_class.must_equal('host_patch')
   end
 
+  it 'should have a collection name' do
+    host_patch_class.collection_name.must_equal(:host_patchs)
+  end
+
   it 'should have an unique id' do
     host_patch_class.read_identity.must_equal(:reference)
   end
@@ -42,4 +46,8 @@ def self.read_identity
   it "shouldn't have default values" do
     host_patch_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    host_patch_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/host_spec.rb b/spec/fog/compute/xen_server/models/host_spec.rb
index 7bbb2f5..dfcc7a3 100644
--- a/spec/fog/compute/xen_server/models/host_spec.rb
+++ b/spec/fog/compute/xen_server/models/host_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     host_class.provider_class.must_equal('host')
   end
 
+  it 'should have a collection name' do
+    host_class.collection_name.must_equal(:hosts)
+  end
+
   it 'should have an unique id' do
     host_class.read_identity.must_equal(:reference)
   end
@@ -99,4 +103,8 @@ def self.read_identity
   it "shouldn't have default values" do
     host_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    host_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/network_spec.rb b/spec/fog/compute/xen_server/models/network_spec.rb
index 98bf445..e1c30ac 100644
--- a/spec/fog/compute/xen_server/models/network_spec.rb
+++ b/spec/fog/compute/xen_server/models/network_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     network_class.provider_class.must_equal('network')
   end
 
+  it 'should have a collection name' do
+    network_class.collection_name.must_equal(:networks)
+  end
+
   it 'should have an unique id' do
     network_class.read_identity.must_equal(:reference)
   end
@@ -50,4 +54,8 @@ def self.read_identity
                                             :name => '',
                                             :other_config => {})
   end
+
+  it 'should require 1 attribute before save' do
+    network_class.require_before_save.must_equal([ :name ])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/pbd_spec.rb b/spec/fog/compute/xen_server/models/pbd_spec.rb
index eb11fc9..56d28af 100644
--- a/spec/fog/compute/xen_server/models/pbd_spec.rb
+++ b/spec/fog/compute/xen_server/models/pbd_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     pbd_class.provider_class.must_equal('PBD')
   end
 
+  it 'should have a collection name' do
+    pbd_class.collection_name.must_equal(:pbds)
+  end
+
   it 'should have an unique id' do
     pbd_class.read_identity.must_equal(:reference)
   end
@@ -37,4 +41,8 @@ def self.read_identity
   it "shouldn't have default values" do
     pbd_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    pbd_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/pci_spec.rb b/spec/fog/compute/xen_server/models/pci_spec.rb
index 2aa150e..df7f7ba 100644
--- a/spec/fog/compute/xen_server/models/pci_spec.rb
+++ b/spec/fog/compute/xen_server/models/pci_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     pci_class.provider_class.must_equal('PCI')
   end
 
+  it 'should have a collection name' do
+    pci_class.collection_name.must_equal(:pcis)
+  end
+
   it 'should have an unique id' do
     pci_class.read_identity.must_equal(:reference)
   end
@@ -37,4 +41,8 @@ def self.read_identity
   it "shouldn't have default values" do
     pci_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    pci_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/pgpu_spec.rb b/spec/fog/compute/xen_server/models/pgpu_spec.rb
index 279616c..5ccc4cc 100644
--- a/spec/fog/compute/xen_server/models/pgpu_spec.rb
+++ b/spec/fog/compute/xen_server/models/pgpu_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     pgpu_class.provider_class.must_equal('PGPU')
   end
 
+  it 'should have a collection name' do
+    pgpu_class.collection_name.must_equal(:pgpus)
+  end
+
   it 'should have an unique id' do
     pgpu_class.read_identity.must_equal(:reference)
   end
@@ -38,4 +42,8 @@ def self.read_identity
   it "shouldn't have default values" do
     pgpu_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    pgpu_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/pif_metrics_spec.rb b/spec/fog/compute/xen_server/models/pif_metrics_spec.rb
index bc63629..55548ce 100644
--- a/spec/fog/compute/xen_server/models/pif_metrics_spec.rb
+++ b/spec/fog/compute/xen_server/models/pif_metrics_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     pif_metrics_class.provider_class.must_equal('PIF_metrics')
   end
 
+  it 'should have a collection name' do
+    pif_metrics_class.collection_name.must_equal(:pifs_metrics)
+  end
+
   it 'should have an unique id' do
     pif_metrics_class.read_identity.must_equal(:reference)
   end
@@ -42,4 +46,8 @@ def self.read_identity
   it "shouldn't have default values" do
     pif_metrics_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    pif_metrics_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/pif_spec.rb b/spec/fog/compute/xen_server/models/pif_spec.rb
index f50b21d..21ec0e1 100644
--- a/spec/fog/compute/xen_server/models/pif_spec.rb
+++ b/spec/fog/compute/xen_server/models/pif_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     pif_class.provider_class.must_equal('PIF')
   end
 
+  it 'should have a collection name' do
+    pif_class.collection_name.must_equal(:pifs)
+  end
+
   it 'should have an unique id' do
     pif_class.read_identity.must_equal(:reference)
   end
@@ -78,4 +82,8 @@ def self.read_identity
   it "shouldn't have default values" do
     pif_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    pif_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/pool_patch_spec.rb b/spec/fog/compute/xen_server/models/pool_patch_spec.rb
index f335b03..af15f8c 100644
--- a/spec/fog/compute/xen_server/models/pool_patch_spec.rb
+++ b/spec/fog/compute/xen_server/models/pool_patch_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     pool_patch_class.provider_class.must_equal('pool_patch')
   end
 
+  it 'should have a collection name' do
+    pool_patch_class.collection_name.must_equal(:pool_patchs)
+  end
+
   it 'should have an unique id' do
     pool_patch_class.read_identity.must_equal(:reference)
   end
@@ -40,4 +44,8 @@ def self.read_identity
   it "shouldn't have default values" do
     pool_patch_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    pool_patch_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/pool_spec.rb b/spec/fog/compute/xen_server/models/pool_spec.rb
index f5d887f..2a219e5 100644
--- a/spec/fog/compute/xen_server/models/pool_spec.rb
+++ b/spec/fog/compute/xen_server/models/pool_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     pool_class.provider_class.must_equal('pool')
   end
 
+  it 'should have a collection name' do
+    pool_class.collection_name.must_equal(:pools)
+  end
+
   it 'should have an unique id' do
     pool_class.read_identity.must_equal(:reference)
   end
@@ -66,4 +70,8 @@ def self.read_identity
   it "shouldn't have default values" do
     pool_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    pool_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/role_spec.rb b/spec/fog/compute/xen_server/models/role_spec.rb
index 014855c..834d9a3 100644
--- a/spec/fog/compute/xen_server/models/role_spec.rb
+++ b/spec/fog/compute/xen_server/models/role_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     role_class.provider_class.must_equal('role')
   end
 
+  it 'should have a collection name' do
+    role_class.collection_name.must_equal(:roles)
+  end
+
   it 'should have an unique id' do
     role_class.read_identity.must_equal(:reference)
   end
@@ -35,4 +39,8 @@ def self.read_identity
   it "shouldn't have default values" do
     role_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    role_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/server_appliance_spec.rb b/spec/fog/compute/xen_server/models/server_appliance_spec.rb
index 319c2cb..eeedef4 100644
--- a/spec/fog/compute/xen_server/models/server_appliance_spec.rb
+++ b/spec/fog/compute/xen_server/models/server_appliance_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     server_appliance_class.provider_class.must_equal('VM_appliance')
   end
 
+  it 'should have a collection name' do
+    server_appliance_class.collection_name.must_equal(:server_appliances)
+  end
+
   it 'should have an unique id' do
     server_appliance_class.read_identity.must_equal(:reference)
   end
@@ -38,4 +42,8 @@ def self.read_identity
   it "shouldn't have default values" do
     server_appliance_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    server_appliance_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/server_metrics_spec.rb b/spec/fog/compute/xen_server/models/server_metrics_spec.rb
index dca4825..7628521 100644
--- a/spec/fog/compute/xen_server/models/server_metrics_spec.rb
+++ b/spec/fog/compute/xen_server/models/server_metrics_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     server_metrics_class.provider_class.must_equal('VM_metrics')
   end
 
+  it 'should have a collection name' do
+    server_metrics_class.collection_name.must_equal(:servers_metrics)
+  end
+
   it 'should have an unique id' do
     server_metrics_class.read_identity.must_equal(:reference)
   end
@@ -45,4 +49,8 @@ def self.read_identity
   it "shouldn't have default values" do
     server_metrics_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    server_metrics_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/server_spec.rb b/spec/fog/compute/xen_server/models/server_spec.rb
index ee624f9..9eaa381 100644
--- a/spec/fog/compute/xen_server/models/server_spec.rb
+++ b/spec/fog/compute/xen_server/models/server_spec.rb
@@ -18,6 +18,10 @@ def self.read_identity
     server_class.provider_class.must_equal('VM')
   end
 
+  it 'should have a collection name' do
+    server_class.collection_name.must_equal(:servers)
+  end
+
   it 'should have an unique id' do
     server_class.read_identity.must_equal(:reference)
   end
@@ -180,6 +184,10 @@ def self.read_identity
                                            :vcpus_params => {})
   end
 
+  it 'should require 1 attribute before save' do
+    server_class.require_before_save.must_equal([ :name ])
+  end
+
   describe '#tools_installed?' do
     describe 'when guest_metrics is nil' do
       it 'should return false' do
diff --git a/spec/fog/compute/xen_server/models/storage_manager_spec.rb b/spec/fog/compute/xen_server/models/storage_manager_spec.rb
index f4305a0..3bb0787 100644
--- a/spec/fog/compute/xen_server/models/storage_manager_spec.rb
+++ b/spec/fog/compute/xen_server/models/storage_manager_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     storage_manager_class.provider_class.must_equal('SM')
   end
 
+  it 'should have a collection name' do
+    storage_manager_class.collection_name.must_equal(:storage_managers)
+  end
+
   it 'should have an unique id' do
     storage_manager_class.read_identity.must_equal(:reference)
   end
@@ -43,4 +47,8 @@ def self.read_identity
   it "shouldn't have default values" do
     storage_manager_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    storage_manager_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/storage_repository_spec.rb b/spec/fog/compute/xen_server/models/storage_repository_spec.rb
index 68f5858..9e1950f 100644
--- a/spec/fog/compute/xen_server/models/storage_repository_spec.rb
+++ b/spec/fog/compute/xen_server/models/storage_repository_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     storage_repository_class.provider_class.must_equal('SR')
   end
 
+  it 'should have a collection name' do
+    storage_repository_class.collection_name.must_equal(:storage_repositories)
+  end
+
   it 'should have an unique id' do
     storage_repository_class.read_identity.must_equal(:reference)
   end
@@ -56,4 +60,8 @@ def self.read_identity
                                                        :physical_size => '0', 
                                                        :sm_config => {})
   end
+
+  it 'should require 2 attributes before save' do
+    storage_repository_class.require_before_save.must_equal([ :name, :type ])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/tunnel_spec.rb b/spec/fog/compute/xen_server/models/tunnel_spec.rb
index 4431a12..85c4e8f 100644
--- a/spec/fog/compute/xen_server/models/tunnel_spec.rb
+++ b/spec/fog/compute/xen_server/models/tunnel_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     tunnel_class.provider_class.must_equal('tunnel')
   end
 
+  it 'should have a collection name' do
+    tunnel_class.collection_name.must_equal(:tunnels)
+  end
+
   it 'should have an unique id' do
     tunnel_class.read_identity.must_equal(:reference)
   end
@@ -37,4 +41,8 @@ def self.read_identity
   it "shouldn't have default values" do
     tunnel_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    tunnel_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/vbd_metrics_spec.rb b/spec/fog/compute/xen_server/models/vbd_metrics_spec.rb
index 848edda..042bc92 100644
--- a/spec/fog/compute/xen_server/models/vbd_metrics_spec.rb
+++ b/spec/fog/compute/xen_server/models/vbd_metrics_spec.rb
@@ -16,6 +16,10 @@ def self.read_identity
     vbd_metrics_class.provider_class.must_equal('VBD_metrics')
   end
 
+  it 'should have a collection name' do
+    vbd_metrics_class.collection_name.must_equal(:vbds_metrics)
+  end
+
   it 'should have an unique id' do
     vbd_metrics_class.read_identity.must_equal(:reference)
   end
@@ -37,6 +41,10 @@ def self.read_identity
     vbd_metrics_class.default_values.must_equal({})
   end
 
+  it "shouldn't require attributes before save" do
+    vbd_metrics_class.require_before_save.must_equal([])
+  end
+
   describe '#last_updated' do
     before :each do
       vbd_metrics.last_updated = XMLRPC::DateTime.new(2000, 7, 8, 10, 20, 34)
diff --git a/spec/fog/compute/xen_server/models/vbd_spec.rb b/spec/fog/compute/xen_server/models/vbd_spec.rb
index 4fc5f58..82966b1 100644
--- a/spec/fog/compute/xen_server/models/vbd_spec.rb
+++ b/spec/fog/compute/xen_server/models/vbd_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     vbd_class.provider_class.must_equal('VBD')
   end
 
+  it 'should have a collection name' do
+    vbd_class.collection_name.must_equal(:vbds)
+  end
+
   it 'should have an unique id' do
     vbd_class.read_identity.must_equal(:reference)
   end
@@ -62,4 +66,8 @@ def self.read_identity
                                         :type => 'Disk', 
                                         :userdevice => '0')
   end
+
+  it 'should require 2 attributes before save' do
+    vbd_class.require_before_save.must_equal([ :vdi, :server ])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/vdi_spec.rb b/spec/fog/compute/xen_server/models/vdi_spec.rb
index 817a0a7..092d812 100644
--- a/spec/fog/compute/xen_server/models/vdi_spec.rb
+++ b/spec/fog/compute/xen_server/models/vdi_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     vdi_class.provider_class.must_equal('VDI')
   end
 
+  it 'should have a collection name' do
+    vdi_class.collection_name.must_equal(:vdis)
+  end
+
   it 'should have an unique id' do
     vdi_class.read_identity.must_equal(:reference)
   end
@@ -70,4 +74,8 @@ def self.read_identity
                                         :tags => 'system',
                                         :virtual_size => '8589934592')
   end
+
+  it 'should require 2 attributes before save' do
+    vdi_class.require_before_save.must_equal([ :name, :storage_repository ])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/vif_metrics_spec.rb b/spec/fog/compute/xen_server/models/vif_metrics_spec.rb
index 44df69f..d00c570 100644
--- a/spec/fog/compute/xen_server/models/vif_metrics_spec.rb
+++ b/spec/fog/compute/xen_server/models/vif_metrics_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     vif_metrics_class.provider_class.must_equal('VIF_metrics')
   end
 
+  it 'should have a collection name' do
+    vif_metrics_class.collection_name.must_equal(:vifs_metrics)
+  end
+
   it 'should have an unique id' do
     vif_metrics_class.read_identity.must_equal(:reference)
   end
@@ -34,4 +38,8 @@ def self.read_identity
   it "shouldn't have default values" do
     vif_metrics_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    vif_metrics_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/vif_spec.rb b/spec/fog/compute/xen_server/models/vif_spec.rb
index 1b20cc6..566ed4e 100644
--- a/spec/fog/compute/xen_server/models/vif_spec.rb
+++ b/spec/fog/compute/xen_server/models/vif_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     vif_class.provider_class.must_equal('VIF')
   end
 
+  it 'should have a collection name' do
+    vif_class.collection_name.must_equal(:vifs)
+  end
+
   it 'should have an unique id' do
     vif_class.read_identity.must_equal(:reference)
   end
@@ -61,4 +65,8 @@ def self.read_identity
                                         :qos_algorithm_params => {}, 
                                         :qos_algorithm_type => 'ratelimit')
   end
+
+  it 'should require 2 attributes before save' do
+    vif_class.require_before_save.must_equal([ :server, :network ])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/vlan_spec.rb b/spec/fog/compute/xen_server/models/vlan_spec.rb
index b6aecbe..7b1969b 100644
--- a/spec/fog/compute/xen_server/models/vlan_spec.rb
+++ b/spec/fog/compute/xen_server/models/vlan_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     vlan_class.provider_class.must_equal('VLAN')
   end
 
+  it 'should have a collection name' do
+    vlan_class.collection_name.must_equal(:vlans)
+  end
+
   it 'should have an unique id' do
     vlan_class.read_identity.must_equal(:reference)
   end
@@ -37,4 +41,8 @@ def self.read_identity
   it "shouldn't have default values" do
     vlan_class.default_values.must_equal({})
   end
+
+  it 'should require 1 attribute before save' do
+    vlan_class.require_before_save.must_equal([ :tag ])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/vmpp_spec.rb b/spec/fog/compute/xen_server/models/vmpp_spec.rb
index 395fc45..660fbd6 100644
--- a/spec/fog/compute/xen_server/models/vmpp_spec.rb
+++ b/spec/fog/compute/xen_server/models/vmpp_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     vmpp_class.provider_class.must_equal('VMPP')
   end
 
+  it 'should have a collection name' do
+    vmpp_class.collection_name.must_equal(:vmpps)
+  end
+
   it 'should have an unique id' do
     vmpp_class.read_identity.must_equal(:reference)
   end
@@ -52,4 +56,8 @@ def self.read_identity
   it "shouldn't have default values" do
     vmpp_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    vmpp_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file
diff --git a/spec/fog/compute/xen_server/models/vtpm_spec.rb b/spec/fog/compute/xen_server/models/vtpm_spec.rb
index a57db24..9734c22 100644
--- a/spec/fog/compute/xen_server/models/vtpm_spec.rb
+++ b/spec/fog/compute/xen_server/models/vtpm_spec.rb
@@ -14,6 +14,10 @@ def self.read_identity
     vtpm_class.provider_class.must_equal('VTPM')
   end
 
+  it 'should have a collection name' do
+    vtpm_class.collection_name.must_equal(:vtpms)
+  end
+
   it 'should have an unique id' do
     vtpm_class.read_identity.must_equal(:reference)
   end
@@ -33,4 +37,8 @@ def self.read_identity
   it "shouldn't have default values" do
     vtpm_class.default_values.must_equal({})
   end
+
+  it "shouldn't require attributes before save" do
+    vtpm_class.require_before_save.must_equal([])
+  end
 end
\ No newline at end of file