The Abstract option specifies that the class is abstract. In Rational Rose, the Abstract option is available along with the options for entity or process classes.
In Rational Software Architect, this option is not listed along with the other IBM Cúram Social Program Management -specific stereotype properties in the Properties tab. Instead, the standard Rational Software Architect abstract option is used for this. In order to specify that the class is abstract you need to place a check in the 'Abstract' checkbox which can be found in the General tab.