Il gruppo di lavoro di Herbert van de Sompel, all'interno del progetto ADORE, ha rilasciato un tool di gestione dei metadati MPEG21-DIDL. I DIDL sono XML codificato per la rappresentazione di oggetti digitali complessi, e sono adoperati presso il Los Alamos National Laboratory per la gestione del repository OAI-PMH compatibile ADORE.
L'MPEG21-DIDL "recognizes the following entities (…):
- An Item is a grouping of Items and/or Components. In the XML representation, an Item is accommodated by the didl:Item element
- A Component is a grouping of Resources. Multiple Resources in the same Component are considered equivalent and consequently an agent may use any one of them. In the XML representation, a Component is accommodated by the didl:Component element
- A Resource is an individual datastream. In the XML Schema, a Resource is accommodated by the didl:Resource element
- Secondary information pertaining to a Container, an Item, or a Component can be conveyed by means of a Descriptor. In the XML representation, a Descriptor is accommodated by the didl:Descriptor element. By definition, a didl:Descriptor is associated with its parent element in the XML representation. For example, a didl:Descriptor provided as a child element of a didl:Component is associated with that didl:Component."
Il tool per la gestione dei metadati MPEG-DIDL è un "Java toolkit for the construction, validation, serialization and de-serialization for MPEG-21 DIDL data model. DIDL, the MPEG-21 Digital Item Declaration Language, provides a hierarchical structure which allows each digital item to be modeled in the most appropriate fashion. The DID API allows for the construction of customized DID models, as well as provides flexible and extensible serialization methods. Key Interfaces:
- Content Type – a simple interface for the addition of new DIDL Statement Content Types (i.e. DII, DCTERMS, XML-Signatures, etc.)
- Serialization – interface for the serialization of DID object objects and constituent content types and resource
- De-serialization – interface for the de-serialization of DID object objects and constituent content types and resource."