Coherent meta data is what is left over after all conflicting values within a collection of meta data are removed. Coherent meta data differs from normally merged meta data in that it omits all entries which have the same name, but differing values. A single instance of meta data is always coherent, as names must be unique.

For example, if one instance in the collection contains the datum colour=red and another contains the datum colour=blue, the coherent set will not contain any entry for colour at all. Normally merged meta data will retain one of the conflicting values.