Definition: Dark refers to any property, set, element, or value unknown to an application at a given time.

Description: The derivation of the word dark came from a discussion during the design of MXF where one contributor remarked. This means you could have an MXF file with a few kilobytes of essence, but gigabytes of metadata that you would not be able to understand. It s like DarkMatter in the universe: You know it has to be there, but you don t know what it s for. From that point onwards, the term dark metadata has been used to describe unknown metadata.

Why should we care about dark metadata, or dark essence, or dark anything? One of the key points of MXF is that it should be extensible. This means that we should be able to create new MXF encoders that create files with new properties and sets. When these files are read by older encoders, the meaning of these sets will be unknown or dark.

The concept of dark data may occur for other reasons. A vendor who creates a store-and-forward device based on MXF is unlikely to implement the full fanctionality of an MXF-based editor. A store-and-forward device probably only needs to be able to identify the UMIDs within the packages and some basic MXF sets. There will be a lot of metadata in the file that the device will not be able to recognize and will thus be forced to treat as...