Graphivac is a software to make and visualize HVAC diagrams.

Symbols are the link between the object on the grid and its visual representation.

Internally, symbols are identified by a hierarchical ID, such as “duct.sensor.temperature”. This hierarchical identification allows Graphivac to fallback to a higher level in case a given symbol is not found.

For example, an organization may use “duct.sensor.temperature.johnson-controls.TE-6300” to represent a temperature sensor with a picture of their favorite product. If the user decides to use a new theme, he doesn't have to re-draw every single symbols in existence; he can simply create a more general “duct.sensor” and Graphivac will take care of using it as a fallback if the more precise symbol cannot be found.

While we at HVAC.IO made a basic hierachical system for the few default symbols provided, there is no official standard yet. The community is free to come up with a better system.