Metadata is data about data. Like the author of a novel, their name is not part of the novel but it is information that describes the novel. MISC has strong support for metadata. Every atom can have a metadata map attached to it.
The syntax used for metadata is an @ sign followed by the metadata map.
Metadata can be read and modified using two built-in functions meta and meta=, also meta+ a bootstrapped function which unions the old and new metadata. These respectively return the metadata of the first argument and return a new value with its metadata set. Using meta= instead of @ allows the metadata to be calculated.