Potential licensees can key a DOI number into a Web-based interface to query the master directory. Unique identifiers are important for tracking and identifying content within a publishing house and for identifying content during online commerce transactions. But as a standalone intellectual- property management system, the DOI is limited. Browsers or potential licensees will need to know a specific DOI before they can query the master database. If a DOI is separated from the object it identifies, the ability to uncover ownership, rights, and contact information is lost.
Digital watermarks require special viewing software for seeing and reading the serial numbers.
Some systems work like the DOI in that a central database can be queried to associate a photographer or publisher with a specific serial number. Watermarks are permanent and persist through derivative works. Digital watermarking technology will not prevent copying of photos or files, but it is one way of ensuring that content can be traced to its owner or creator at a later time. Like the DOI, it is only a partial intellectual-property rights management solution. To overcome these problems, companies developing digital watermarks are establishing partnerships with software publishers to integrate the watermark technology into desktop products.