Table 2. OCL rules for the model validation process I.

Rule 1	CloudProvider_must_offer_once_each_VM_for_each_SLA_type
Rule Description	Cloud service provider must offer each VM only once for each SLA type.
Rule OCL Code	context SLA inv self.vmcost->isUnique(vmcost | vmcost.vm)
Notification Type	Error
MSCC Recommendation	Please, enter each VM only once in each SLA!
Rule 2	User_must_sign_a_VM_SLA_offered_by_the_CloudProvider
Rule Description	A User must always sign an SLA offered by the cloud service provider.
Rule OCL Code	context User inv uml2cloud::CloudProvider.allInstances() ->collect(cp | cp.sla)->includes(self.sla)
Notification Type	Error
MSCC Recommendation	Please, sign an SLA!
Rule 3	User_request_a_VM_not_offered_in_the_signed_SLA
Rule Description	A user cannot request a VM, which is not offered in the signed SLA.
Rule OCL Code	context Request inv uml2cloud::User.allInstances() ->select(user | user.base_Lifeline.coveredBy ->includes(self.sendEvent)) ->collect(user | user.sla.vmcost ->collect(vmcost | vmcost.vm)) ->includes(self.vmInstantation.vmType)
Notification Type	Error
MSCC Recommendation	Please, one of the following actions must be performed to resolve the error: 1. A user must request another VM that is in the SLA. 2. A user must sign another SLA including that VM type. 3. The cloud service provider must include that type in this SLA signed by the user!
Rule 4	SLA_base_cost_must_be_greater_than_or_equal_to_zero
Rule Description	The defined base cost value must be greater or equal to zero.
Rule OCL Code	context SLA inv self.vmcost ->forAll(vmcost | vmcost.base.value >= 0)
Notification Type	Error
MSCC Recommendation	Please, enter a positive value for the base cost value!
Rule 5	SLA_inc-priority_cost_must_be_greater_than_or_equal_to_zero
Rule Description	The defined inc-priority cost for high-priority users must be greater or equal to zero.
Rule OCL Code	context SLA inv self.vmcost ->forAll(vmcost | vmcost.incpriority >= 0)
Notification Type	Error
MSCC Recommendation	Please, enter a positive value for the inc-cost cost value!
Rule 6	SLA_discount_must_be_greater_than_or_equal_to_zero
Rule Description	The discount offered to regular users must be greater or equal to zero.
Rule OCL Code	context SLA inv self.vmcost ->forAll(vmcost | vmcost.discount >= 0)
Notification Type	Error
MSCC Recommendation	Please, enter a positive value for the discount value!