Sustainability Criteria and Metrics

Common Quality Criteria and Metrics relate to quality criteria and metrics well known from the standard quality models for software e.g. ISO 25000 (SQuaRE). These are then interpret-ed on the background of their contribution to sustainable development.

Reusability, which is the ability of software components to be reused in other software systems, reduces efforts to develop other software systems and thus reduces environmental impacts of the development phase [1].

Modifiability, the ability to implement changes of software quickly, reduces environmental impacts that result from developing and main-taining a software system [1].

Usability and Accessibility of software contrib-ute to social aspects, as they make software easier to learn, more accessible to users with disabilities, or more accessible to people with-out access to computers with sufficient per-formance or screen sizes [1].

Predictability, which refers to the development process itself, is the ability of the developers to accurately estimate person-days for required features. This contributes to social aspects, as it improves the developers’ conditions of work by reducing the probability of overtime work [1].

Directly Related Quality Criteria and Metrics relate to quality properties known from standard quality models, but also introduce new aspects and a new quality property.

The property Efficiency considers aspects like runtime efficiency and usage of computer resources. Appropriate metrics to measure efficiency are CPU-intensity, memory usage, peripheral intensity and idleness. Runtime efficiency directly relates to the property Performance, as runtime efficient programs minimize energy consumption through less computer usage [2]. Hence, it is possible to define energy efficiency metrics for software [3], which relate the work done to the energy consumption of the IT system or components of it. By comparing the measured system with a reference system, it is possible to determine which system is more energy efficient [4].

An aspect newly introduced into the property Portability is hardware obsolescence. It considers the amount of hardware that must be replaced before it has reached the end of its useful lifetime in order to use the new soft-ware [1,3].

The property Feasibility [2] considers how the software engineering process follows and manages sustainability issues during its execution. Main aspects are carbon footprint [5], travel, energy, and waste [2], according to our life cycle of software products.

Indirectly Related Criteria and Metrics subsume quality properties and their supporting metrics that regard how software indirectly affects its usage domain and how software supports sustainable development in its application domain. The first is addressed by the property Reflectivity whereas the latter is addressed by the property Sustainability.
Currently, the property Reflectivity [2] re-quires more research to get easy-to-use and reliable metrics.

The property Sustainability [2] is supported by the aspects fit for purpose, reduction, and beauty. Fit for purpose describes how software helps its application domain to reach its objectives. Reduction considers how the software supports its application domain in waste reduction. Beauty assesses the contribution of the software to sustainable development. To measure the property Sustainability, it is necessary to define a reference software system and to calculate metrics that can then be compared with the same metrics of the system currently under development.

Set of Criteria

1. Albertao, Felipe; Xiao, Jing; Tian, Chunhua; Lu, Yu; Zhang, Kun Qiu; Liu, Cheng (2010): Measuring the Sustainability Performance of Software Projects. In: IEEE Computer Society (ed.): 2010 IEEE 7th Interna-tional Conference on e-Business Engineering (ICEBE 2010), Shanghai, China, pages 369–373.
2. Taina, Juha (2011): Good, Bad, and Beautiful Soft-ware - In Search of Green Software Quality Factors. In: CEPIS UPGRADE, XII, number 4, pages 22–27. www.cepis.org [2012-01-09].
3. Naumann, Stefan; Dick, Markus; Kern, Eva; Johann, Timo (2011): The GREENSOFT Model: A Reference Model for Green and Sustainable Software and its Engineering. In: Sustainable Computing: Informatics and Systems, volume 1, number 4, pages 294–304. doi:10.1016/j.suscom.2011.06.004
4. Dick, Markus; Kern, Eva; Drangmeister, Jakob; Naumann, Stefan; Johann, Timo (2011): Measure-ment and Rating of Software-induced Energy Con-sumption of Desktop PCs and Servers. In: Pillmann, W., Schade, S., Smits, P. (eds.): Innovations in sharing environmental observations and information. Proceedings of the 25th International Conference EnviroInfo October 5 - 7, 2011, Ispra, Italy, Shaker, Aachen, pages 290–299.
5. Taina, Juha (2010): How Green Is Your Software? In: Tyrväinen, P., Cusumano, M. A., Jansen, S. (eds.): Software Business. First International Conference, ICSOB 2010, Jyväskylä, Finland, June 21-23, 2010. Proceedings, Springer-Verlag Berlin Heidelberg, Berlin, Heidelberg, pages 151–162.