To compensate the deficits described, the identifier must be able to
Therefore, two functions must be combined:
This requires unequivocal, location-independent identification systems providing permanent availability of digital objects.
Persistent Identifiers (PI) meet the requirements described. Their basic concept is strict separation of an object's identification from its location reference through an unequivocal string. Instead of URLs, PIs are indicated as identifiers and resolved in the referring URLs via an intermediate so-called resolving mechanism.
PI services require a certain technical and organisational infrastructure to provide long-term availability of services. Therefore, document classes shall be selected for PI assignment and administration.