To provide search capabilities in a process control system, a contextual knowledge repository is generated that organizes process plant-related data according to semantic relations between the process plant-related data and the process plant entities. When a user submits a process plant search query related to process plant entities within a process plant, search results are obtained by identifying a data set from the contextual knowledge repository which is responsive to the process plant search query. The search results are then presented on a user interface device based on the identified data set. To allow for searches to be performed by user interface devices external to the process plant, a data diode is disposed between a field-facing component and an edge-facing component of the process plant so that data flows from the field-facing component to the edge-facing component without flowing from the edge-facing component to the field-facing component.