Quantifying the ilities: A literature review of robustness, interoperability, and agility

Abstract

This paper presents a literature review of the methods for quantifying system ilities. This paper is the second in a series that quantifies the ilities. The ilities are nonfunctional system characteristics. The motivation for designing systems to express these ilities is in response to the ever increasing complexity of engineered systems, increasing requirements on budget and schedule, and the need to adapt to a rapidly changing world. The systems-engineering community has increased its focus on defining and implementing the ilities for over a decade. Many works available in the literature have defined the ilities and their inter-relations. A subset has gone further to quantify the ilities; however, the literature is currently fragmented in its approach. This paper attempts to identify and summarize the various approaches in quantifying the ilities. A systematic literature review was conducted across eight conferences and journals from 2010 to 2015. This paper addresses the findings for robustness, interoperability, and agility, which include definitions or quantifications in 222 documents. The definitions discovered for each of the ilities demonstrated relative agreement; however, many differed in the details. Robustness was found to have a wide number and variety of quantifications. A moderate number of quantifications were found for interoperability, whereas few quantifications were found for agility. It is recommended that further efforts by the community are devoted to the development of quantified measures for interoperability and agility.