It is possible to establish a dynamic correlation between usage record properties in which one usage record property can instantiate another. For example, if a user is specified in a charge but no project is specified then the user's default project should be applied to the account constraints and logged; or if a project is specified in a charge but not its organization then the organization corresponding to that project should be looked up and applied to the account constraints and logged. Three usage record property instantiator types are currently supported and are configured by prefixing the property instance's Values foreign object reference with the appropriate characters: Assign if not defined (@?=), Assign if not different (@!=), Assign always (@:=). We shall look at each of these individually and in different terms.

• Applying a correlated default (@?=) -- If property X is specified with the value x in the usage record and property Y is not specified in the usage record and if the object instance referred to by x has a correlated default value of y' for property Y', then y' will be applied as the default value for property Y in the usage record. For example, we could establish the notion of a default project for a user.

Example 17. Establishing a default project for a user

First we add a DefaultProject attribute (the name is arbitrary) to the User object and give it a Values property of @?=Project.

$ goldsh Attribute Create Object=User Name=DefaultProject DataType=String Values="\"@?=Project\"" Description="\"Default Project\""
Successfully created 1 attribute

Then we can establish the default project for user scottmo to be chemistry.

User Modify Name==scottmo DefaultProject=chemistry
Successfully modifed 1 user

Subsequently, when a Charge, Reserve or Quote is issued that specifies the User scottmo but does not specify the Project, the Project chemistry Project will be applied to the charge as if originally specified in the usage record charge data.

• Applying a correlated verification (@!=) -- If property X is specified with the value x in the usage record and property Y is specified with the value y in the usage record and if the object instance referred to by x has a correlated verification value of y' for the property Y' and if y' does not equal y, then fail with an error message. Additionally, if property X is specified with the value x in the usage record and property Y is not specified in the usage record and if the object instance referred to by x has a correlated verification value of y' for property Y', then y' will be applied as the default value for property Y in the usage record. For example, we could establish a parent-child relationship between organizations and projects in which explicitly specified incongruities result in a failure.

Example 18. Establishing a verification hierarchy with projects and organizations

First we add a VerifyOrganization attribute (the name is arbitrary) to the Project object and give it a Values property of @!=Organization.

$ goldsh Attribute Create Object=Project Name=VerifyOrganization DataType=String Values="\"@!=Organization\"" Description="\"Verify Organization\""
Successfully created 1 attribute

Then we can establish the verify organization for project chemistry to be sciences.

$ goldsh Project Modify Name==chemistry VerifyOrganization=sciences
Successfully modifed 1 project

Subsequently, when a Charge, Reserve or Quote is issued that specifies the Project chemistry and specifies the wrong Organization (e.g. arts), the transaction will fail with an error message. Additionally, when a Charge, Reserve or Quote is issued that specifies the Project chemistry but does not specify the Organization, the Organization sciences will be applied to the charge as if originally specified in the usage record charge data.

• Applying a correlated override (@:=) -- If property X is specified with the value x in the usage record and if the object instance referred to by x has a correlated override value of y' for property Y', then y' will be applied as the override value for property Y in the usage record. For example, we could establish a parent-child relationship between organizations and projects in which explicitly specified incongruities are silently overridden with the value from the child.

Example 19. Establishing an override hierarchy with projects and organizations

First we add an OverrideOrganization attribute (the name is arbitrary) to the Project object and give it a Values property of @:=Organization.

$ goldsh Attribute Create Object=Project Name=OverrideOrganization DataType=String Values="\"@:=Organization\"" Description="\"Override Organization\""
Successfully created 1 attribute

Then we can establish the override organization for project chemistry to be sciences.

$ goldsh Project Modify Name==chemistry OverrideOrganization=sciences
Successfully modifed 1 project

Subsequently, when a Charge, Reserve or Quote is issued that specifies the Project chemistry and specifies either the wrong Organization (e.g. arts) or no Organization, the Organization sciences will be silently applied to the charge as if originally specified in the usage record charge data.