“Assemblying the Jigsaw” is the name of a whitepaper published by ISG in 2013 about the need and the role of Service Integration and Management (SIAM) in multisourced IT environments. The article, which is still available here, provides good guidance regarding success factors and implementation challenges. My experience has also shown that finding the right SIAM model is also essential and tuning it may take a few iterations. There are several alternative SIAM models (internal x external, independent service provider x lead service provider, etc.) and the speed of implementation needs to match the level of maturity of the organisation and the time required to manage the organisational change.