Modularization is considered as one enabler for flexible and highly reconfigurable process plants. These characteristics are needed to overcome deficiencies regarding market volatility and shorter product innovation cycles. Current standardization activities aim at the specification of Module Type Package (MTP) files as a semantic description of modules for fast and efficient integration into process control systems. To increase the plug and produce character of the approach, online discovery for modules has to be enabled. OPC UA is considered as a suitable industrial communication technology for the communication between modules and process control systems. Therefore, this paper presents an approach for the representation of MTPs in OPC UA in order to enable the online discovery of process modules.