In a Service and Integration Management (SIAM) ecosystem, the structure is typically composed of three main layers. The first layer is the customer organization (the consumer of services). The second layer consists of the various internal and external service providers. The third layer, positioned logically between the customer and the providers, is the Service Integrator. This layer is responsible for the end-to-end governance, management, integration, assurance, and coordination of services to ensure they meet the customer's business requirements.

A. Service advocate: This is not a formally defined layer within the SIAM framework; it describes a potential behavior or role, not a structural component.

B. Service installer: This refers to a specific, operational role focused on deploying a service, not the strategic layer responsible for managing multiple providers.

D. Service manager: This is a standard role within service management frameworks but does not represent the entire integration and governance layer unique to a SIAM model.

1. Scopism. (2020). Service Integration and Management (SIAM™) Foundation Body of Knowledge. The Stationery Office (TSO). p. 13, Section 2.2, Figure 2.2. (This foundational text explicitly illustrates the three layers as the Customer Organization, the Service Integrator, and the Service Providers, stating, "The service integrator is logically placed between the customer organization and the service providers...")

2. Wichers, R., & Agutter, M. (2017). VeriSM™: A service management approach for the digital age. Van Haren Publishing. Chapter 5.3.2, "Sourcing Practices." (This official VeriSM guide discusses sourcing models, including SIAM, and the necessity of an integration function, which is the role of the Service Integrator, to manage multi-provider environments.)

3. Peramunugamage, A., & Dissanayake, R. (2019). A Framework for Service Integration and Management (SIAM) in a Multi-sourcing Environment. In Proceedings of the 2019 2nd International Conference on Service-Oriented Computing and Applications (SOCA '19). Association for Computing Machinery, New York, NY, USA, 1–8. (This academic paper analyzes the SIAM model, consistently identifying the "Service Integrator" as the central layer that coordinates between the customer and multiple service providers.) DOI: https://doi.org/10.1145/3375924.3375925