Green Software

Green IT is the study and practice of using computing resources efficiently to reduce negative impacts on the environment. Green IT is applicable to various hightech domains, such as datacenters, mobile computing, and embedded systems.

Although software systems don’t consume energy directly, they affect hardware utilization, leading to indirect energy consumption. Therefore, it’s important to engineer software to optimize its energy consumption.

Greening in software aims to reduce the environmental impact caused by the software itself. Therefore, greenness in software is an emerging quality attribute that must be taken into account. Software companies need to deal with the conflict between customer pressure (new functional requirements and a high level of quality) and being as environmentally friendly as possible.

In “Safety, Security, Now Sustainability: The Nonfunctional Requirement for the 21st Century,” authors Birgit Penzenstadler, Ankita Raturi, Debra Richardson, and Bill Tomlinson argue that sustainability (that is, green software) is now considered to be a nonfunctional requirement similar to safety and security.

In addition, the authors highlight the importance of indirect impact of the sustainability requirements: an analyst should consider not only direct effects of the requirements (such as energy consumption) but also indirect effects (such as change in consumer behavior).

In “Analyzing the Harmful Effect of God Class Refactoring on Power Consumption,” Ricardo Pérez-Castillo and Mario Piattini also argue that greenness is in fact a nonfunctional requirement, but they question whether it conflicts with other such requirements. Could greened software be less performant, maintainable, and secure, thereby requiring additional trade-offs? The authors analyze how power consumption changes as an effect of refactoring for maintainability. In this particular case, they found that reducing god classes has a negative effect on consumption.

Green specifications provide a way to indicate a service’s carbon footprint and eventually specify operational constraints to allow more flexibility during service provisioning.

Greening in software aims to reduce the environmental impact caused by the software itself. [...] Green specifications provide a way to indicate a service’s carbon footprint and eventually specify operational constraints to allow more flexibility during service provisioning.

In “Facilitating Greener IT through Green Specifications,” Colin Atkinson, Thomas Schulze, and Sonja Klingert propose a solution that includes environmental aspects as part of a service-level agreement. To test it, they used their approach in an industrial setting in collaboration with a local software-as-aservice provider.

In “Green Software: Greening What and How Much?,” Krzysztof Sierszecki, Tommi Mikkonen, Michaela Steffens, Thomas Fogdal, and Juha Savolainen report the experience and data of a company that develops factory automation systems that can be roughly divided into three parts: computer-controlled drivers, electric motors, and fullfledged industrial applications. The authors analyze the split of consumption (and possible consumption savings) for each part. As expected, greening the IT part brings in a minimal contribution to greening the whole application, so the authors underline the importance of a system approach to addressing the problem.

In “The Impact of User Choice on Energy Consumption,” Chenlei Zhang, Abram Hindle, and Daniel M. German take this viewpoint and analyze the energy consumption of software applications in the same category across several usage scenarios. Perhaps not surprisingly, they find that applications do have different efficiencies, so the authors suggest introducing consumption ratings both to make public the efficiency of software applications and to modify user behavior.

Recent developments have indicated that besides focusing on hardware, the IT industry should also focus on software in terms of sustainability. Software development requires making trade-offs between customer demands and the requirements for corporate social responsibility initiatives.