Uniform Resource Locators (URLs), also commonly known as web addresses, are like house addresses in that they will direct you to a specific location in space (in this case, internet space). But any archaeologist can tell you that no structure lasts forever, and URLs are similarly prone to deterioration. The location of content will often change as websites evolve to keep up with technological developments, rendering old URLs useless as they direct users to addresses where content no longer exists.
Persistent Identifiers (PIDs) are much more like fingerprints – they are unique and identify the content itself rather than solely its location. Digital Object Identifiers (DOIs) are just one example of a PID. Like URLs, DOIs serve as hyperlinks to content, however, they also contain attached metadata such as subject, publisher, and creator in addition to the location to ensure referential integrity. This is what makes DOIs persistent: even if the metadata changes, the actual DOI will never change.
Digital Object Identifiers
While persistence is a major advantage for using DOIs, it is not the only benefit that sets them apart from URLs. For one, URLs vary from website to website and can become extremely lengthy, whereas all DOIs follow the same compact format no matter the type of data they identify. Each DOI includes a resolver (to help access the content), a prefix (identifies the source), and a suffix (identifies the exact object). This standardised identification method promotes consistency across all types of content.
DOIs are incredibly powerful in that they also create a network of related resources. DOI metadata can be searched in portals such as DataCite Commons to find similar and associated content. Conducting research and reviewing existing literature is much quicker and simpler as a result of this collection of metadata. From the perspective of content producers, DOIs are also extremely valuable due to their ability to be tracked. Users who cite the DOI rather than the URL allow the authors to follow the impact of their content and analyse the patterns of its reuse.
DOIs > URLs
In all, the main difference between URLs and PIDs such as DOIs is that URLs only retain one piece of information about a resource (its location) while PIDs retain detailed metadata attributed to a resource. DOIs and other PIDs are therefore secure from issues that URLs face such as link rot, and they also inherently connect related content which facilitates scholarly discourse better than a URL might. So when you cite a DOI rather than a URL, you are promoting digital preservation and encouraging the access and reuse of valuable data.
