OPC Extensible Markup Language (OPC XML) encapsulates process control data making it available across all operating systems using XML. This specification had very few implementations and has largely been abandoned by corporations in favor of OPC DA (OPC Data Access) and OPC UA (OPC Unified Architecture).

The OPC Foundation (www.opcfoundation.org) is responsible for defining and maintaining the OPC XML specification.

See also: OPC DA, OPC UA