The special issue of the Journal of Network and Systems Management focuses on Management of Federations and Cooperative Management. The first article, 'Managed Semantic Interoperability for Federations,' by Brennan and co-researchers recognizes that achieving semantic interoperability between components is a pre-requisite to federating IT systems. The authors address dynamic federations in which autonomous members with heterogeneous data or service description schemata are admitted. Another article, 'Ontology-based Semantic Priority Scheduling for Multidomain Active Measurements,' by Calyam also proposes the use of semantic models, albeit for a very specific purpose, the development of an ontology-based semantic priority scheduling algorithm that prioritizes measurement requests from multiple sources. 'An Iterative Approach to Trustable Systems Management Automation and Fault Handling,' by McLarnon notes that automated management systems are increasingly being used to automate common management tasks for large-scale distributed computing systems.