4.4 Repository namespaces
Each Daisy repository (since Daisy 2.0) has at least one namespace. The documents created in that repository will by default belong to one of those namespaces based on the configuration. The ID of a document is the combination of a numeric sequence and the namespace, for example:
Each repository server is responsible for maintaining the sequence number for the documents of their namespace. When a document is created with a foreign namespace (a namespace that is not managed by the current repository server), the sequence ID needs to be supplied, since it is assumed that another repository server is responsible for that namespace. On the other hand, when a document is created in the namespace that is managed by repository server itself, then a sequence ID cannot be supplied, as the repository server itself is then responsible for assigning the sequence ID.
A Daisy repository server doesn't really care whether foreign namespaces are really associated with other repository servers. The namespace could also come from an external application that creates documents (and maintains its own sequence counter), it could come from a manually created 'export' that is imported using the import tool, or a namespace created by an administrator. So for foreign namespaces, it just assumes someone else is responsible for assigning unique sequence numbers.
4.4.1 Namespace name
A namespace can be up to 200 characters and contain the characters a-z, A-Z, 0-9 and _ (underscore). The dot character is not allowed to avoid confusion with file name extensions (as the document ID will often be used in URLs), and the dash character is not allowed to avoid confusion with the separator between the sequence number and the namespace.
The namespace name is typically a short string. This approach has been choosen to keep the document IDs short and readable. But as a consequence, it requires some care to avoid conflicting namespaces within an organisation, and between organisations there's no control whatsoever.
If you want to avoid the possibilities of conflicts and don't care about the readability, it is always possible to use a longer string. For example, a registered domain name or a random generated string (GUID). However, in general we would recommend to stick with a short name.
The repository server installation tool gives some recommendations on namespace naming.