Policy Server Guides › Policy Server Configuration Guide › Enterprise Policy Management › EPM Use Cases for Protecting Applications › Application Security Policies with User Mapping and Named Expressions › Define Named Expressions to Check the Credit Limit

Define Named Expressions to Check the Credit Limit

Named expressions enable SiteMinder to calculate each users credit limit and account balances. An expression can also determine if customers are over their credit limit.

To define named expressions for this use case

1. Define a virtual user attribute that calculates a $1,000 dollar credit limit for customers and a $2,000 credit limit for employees:
   • Name the attribute #CreditLimit.
   • Define #CreditLimit as:

     IsCustomer?1000:2000
     

     This calculation contains SiteMinder supported expression syntax.

2. Define a virtual user attribute that retrieves account balances from the accounting database:
   • Name the attribute #Balance
   • Define the attribute as:

     (MyLibrary.GetBalance(""))
     

     This attribute definition is an active expression defined by the clothing retailer.

3. Create a user class expression that determines if customers are over their credit limit:
   • Name the attribute @IsUnderCreditLimit
   • Define the attribute as:

     (#Balance > #CreditLimit)
     

Read Define Named Expressions for details on creating virtual user attributes and user class expressions.