13. A system for dynamic document retention in a multi-owner environment that includes a document management system, comprising: a memory; and a processor cooperatively operable with the memory, and configured to, based on instructions stored in the memory, register, in a retention service, a plurality of document owners as owners of a same document; register, in a plug-in registry, as registered retention policies, different document retention policies related to the same document, the different document retention policies being managed, defined, and provided by the plurality of document owners; trigger, a retrieval, from at least one of the plurality of document owners, of an update to at least one of the registered retention policies, which is registered in the plug-in registry, wherein the update includes at least whether the same document is still needed by the at least one of the plurality of document owners or whether the same document may be deleted; modify, in the retention service, when the update is that the same document may be deleted, document owners registered as owners of the same document by deleting the at least one of the plurality of owners as a registered owner of the same document, and adjusting downward a document-owner-count for the same document that counts the document owners; and perform a first determination, based on the document-owner-count, as to whether there is at least one document owner of the same document, and when the first determination is that there is not at least one owner of the same document, delete or archive or move to a recycle bin the same document, otherwise perform a second determination as to whether each of the owner-defined document retention policies which are registered for the at least one document owner of the same document separately confirms that the same document can be deleted or archived or moved to the recycle bin, and when the second determination is that each of the owner-defined document retention policies which are registered for the at least one document owner of the same document does confirm that the same document can be deleted or archived or moved to the recycle bin, delete or archive or move to the recycle bin the same document, otherwise perform a third determination as to whether an override document retention policy assigned to the same document requires the same document to be archived or deleted or moved to the recycle bin, and when the third determination is that an override document retention policy assigned to the same document does require the same document to be archived or deleted or moved to the recycle bin, delete, archive, or move to the recycle bin the same document, wherein: the retention service and the plug-in registry are part of a document management system, and the document retention policies managed, defined, and provided by the plurality of document owners may be responsive to events occurring internal to the document management system, to events occurring external to the document management system, and to timing.
13. A system for dynamic document retention in a multi-owner environment that includes a document management system, comprising: a memory; and a processor cooperatively operable with the memory, and configured to, based on instructions stored in the memory, register, in a retention service, a plurality of document owners as owners of a same document; register, in a plug-in registry, as registered retention policies, different document retention policies related to the same document, the different document retention policies being managed, defined, and provided by the plurality of document owners; trigger, a retrieval, from at least one of the plurality of document owners, of an update to at least one of the registered retention policies, which is registered in the plug-in registry, wherein the update includes at least whether the same document is still needed by the at least one of the plurality of document owners or whether the same document may be deleted; modify, in the retention service, when the update is that the same document may be deleted, document owners registered as owners of the same document by deleting the at least one of the plurality of owners as a registered owner of the same document, and adjusting downward a document-owner-count for the same document that counts the document owners; and perform a first determination, based on the document-owner-count, as to whether there is at least one document owner of the same document, and when the first determination is that there is not at least one owner of the same document, delete or archive or move to a recycle bin the same document, otherwise perform a second determination as to whether each of the owner-defined document retention policies which are registered for the at least one document owner of the same document separately confirms that the same document can be deleted or archived or moved to the recycle bin, and when the second determination is that each of the owner-defined document retention policies which are registered for the at least one document owner of the same document does confirm that the same document can be deleted or archived or moved to the recycle bin, delete or archive or move to the recycle bin the same document, otherwise perform a third determination as to whether an override document retention policy assigned to the same document requires the same document to be archived or deleted or moved to the recycle bin, and when the third determination is that an override document retention policy assigned to the same document does require the same document to be archived or deleted or moved to the recycle bin, delete, archive, or move to the recycle bin the same document, wherein: the retention service and the plug-in registry are part of a document management system, and the document retention policies managed, defined, and provided by the plurality of document owners may be responsive to events occurring internal to the document management system, to events occurring external to the document management system, and to timing. 24. The system of claim 13 , wherein the trigger of the retrieval of the update to at least one of the registered retention policies, as a push mechanism, is by the at least one of the plurality of document owners.