Guest editorial—second part of special issue on cloud computing

In this issue we continue with our selection of papers highlighting innovative work on cloud computing. This time we cover naming and resource location, virtual machine placement, scheduling work on hybrid clouds, and authorization management. In “A XRI Naming System for Dynamic and Federated Clouds: a Performance Analysis”, Antonio Celesti, Massimo Villari, and Antonio Puliafito investigate the challenges in providing a common naming and location service for identifying virtual resources residing in different operating systems. They describe and evaluate an approach for extending the OpenXRI architecture to provide a front-end for cloud name space management. The paper “HCOC: a cost optimization algorithm for workflow scheduling in hybrid clouds”, by Luiz Fernando Bittencourt and Edmundo Roberto Mauro Madeira, looks at the problem of dynamically extending private clouds by adding resources from public clouds. They propose an algorithm to decide when to lease resources from a public cloud in order to execute a workflow within a specified execution time.