DOIs take the form of a identifier prefix followed by a suffix which are separated by a forward slash, I.e.

```
prefix/suffix
```

The prefix identifies the registrant of the DOI, that is, the entity who registered the identifier. The suffix represents a single object. By incrementing the suffix a single prefix can be used to reference multiple objects. For example, the handle 10/1234 identifies the entity with prefix "10" and an item which the entity would like to provide a reference to is identified using the suffix 1234. Some identifiers prepend additional identifiers which represent the namespace being used. In the case of Quadratic Identifiers, "64" is prepended to the prefix to differentiate it from other services. For example:

```
64.10/1234
```
 	
 where 64 is the Quadratic Identifier namespace, 10 is the registrant's prefix and 1234 is the id of the item.

DOIs are particularly useful for entities with multiple items. For example, a journal can be represented using a unique prefix and the issues of that journal could be identified using a sequentially increasing suffix.

Additionally, what Quadratic Identifiers represent can be expanded to other digital objects, and not necessarily be confined to public works. Unlike Handle.net or DOI, Qu.Ids could also represent authorship such as a handle to a contributor profile. 