1. A security controller apparatus for providing messaging services on a data exchange layer (DXL), comprising: a memory communicatively coupled to one or more processors; a network interface; a DXL services engine operable for providing an application programming interface (API) for connecting to a DXL enterprise service bus (ESB) via the network interface, wherein the DXL is configured to provide a context-aware producer-consumer framework on a service-oriented architecture; and a domain security engine operable for consuming security events via the DXL, and configured for: subscribing to a DXL security topic as a DXL consumer; consuming a security event related to the DXL security topic via the DXL ESB; as a DXL producer, publishing a DXL security message via the DXL ESB, wherein the DXL security message is configured to enable a DXL consumer to act on the security message; consolidating a plurality of DXL messages; building a context-sensitive security policy, comprising assigning a location-independent security policy to a DXL endpoint, and publishing the assignment via a DXL message; publishing the context-sensitive security policy via a DXL message; and providing security information and event management (SIEM) services according to the DXL security message, comprising pooling data from a plurality of dissimilar resources and normalizing the data for consumption via the DXL.