Middleware for multicloud

Guest Editors' Introduction: There are many different options available to implement information technology (IT) today: enterprise data center legacy approaches or private cloud, public cloud, hybrid cloud, fog, device, mobile edge, and multicloud. Although definitions vary, for a variety of reasons, many companies are using multicloud approaches in a variety of patterns, at various layers such as infrastructure as a service (IaSS) and software as a service (SaaS).1 In some cases, multiple SaaS or infrastructure public or private clouds are used to support an end-to-end process, sometimes called workflow enactment.2 For example, a purchase order might be sent via a (cloud-based SaaS) email service such as Gmail, processed in a private cloud application, and then billed via a (cloud-based SaaS) billing service such as Zuora. Other use cases involve multiple public infrastructure clouds. For example, Netflix famously uses Amazon Web Services (AWS) for digital movie transcoding and its entertainment recommendation engine, but it also backs up data to Google's cloud in the event of an AWS outage. This special issue contributes to the advancement of the area of Multicloud middleware by presenting concrete solutions and ongoing efforts to address different aspects of Multicloud middleware development and operation.