While planning the redesign of an enterprise application at my employer, we’re using the Microsoft patterns & practices Application Architecture Guide as one of our design guides.

We started by baselining the current application against the guide, and found it deficient in every single outlined quality attribute. Specifically, the quality attributes outlined are availability, conceptual integrity, flexibility, interoperability, maintainability, manageability, performance, reliability, reusability, scalability, security, supportability, testability, and usability. Unfortunately, these deficiencies are what lead to the biggest pain points, both for the business and the technologists trying their level best to deliver the optimal solution to it.

Obviously, there are tradeoffs inherent in these quality attributes. One obvious tradeoff is security versus performance and usability. All three are important in nearly every application, but depending upon the threat profile of the application, security may take precedence over nearly every other attribute.

According to the document, during the design process, the following guidelines should be considered:

  • Quality attributes are system properties that are separate from the functionality of the system.
  • From a technical perspective, implementing quality attributes can differentiate a good system from a bad one.
  • There are two types of quality attributes: those that are measured at run-time, and those that can only be estimated through inspection.
  • Analyze the tradeoffs between quality attributes.

Some of the questions from the guide include:

  • What are the key quality attributes required for your application? Identify them as part of the design process.
  • What are the key requirements for addressing these attributes? Are they actually quantifiable?
  • What are the acceptance criteria that will indicate you have met the requirements?