Problem statement:A well designed user interface is comprehensible and controllable, helping users to complete their work successfully and efficiently and to feel competent and satisfied. To improve the usability of a software system, usability patterns can be applied. However, there are short comes shows that the software architecture of a system restricts certain usability patterns from being modified after implementation. Several of these usability patterns are "architecture sensitive", such modifications are costly to implement due through their structural impact on the system. So we practice the pattern oriented usability design with considering the dependencies between the design decisions relevant to the product line business objects which has its impact on the usability criterion. Dependencies between the rationale decisions for the architecture sensitive usability patterns can be maintained for future reference. Approach: While going for the usability patterns, the decisions behind the pattern selection should be specified. We address the issues by analyzing the quality based models that determines the design rationale and their dependencies. We use QDK methodology to preserve the specifications of decisions and all their inter dependencies along with the knowledge rule. Results: Preserving the specifications of decisions and all their inter dependencies with knowledge rules will support the evolution and maintenance of such productline systems. Explicit evaluation of usability during architectural design prevents part of the high costs incurred by adaptive maintenance activities once the system has been implemented. Conclusion: Capturing knowledge by this means provides the basis for justification, learning and re-uses of the knowledge rules for further design decisions.