The Dublin core is a metadata — data that provides information about other data, such as that found in a library database — standard that helps to describe networked resources. It is a basic element set with two levels. Simple is the base level; it has fifteen elements that are used to catalog and describe a resource. The qualified level has fewer elements and serves to refine the entry so that it is easier to find and understand. Dublin core elements are used in places such as libraries and museums and in fields including text encoding and computer science to organize and aid in the discovery of information. They are most commonly found in scholarly settings.
Simple core level consists of 15 standard text fields that are used to describe a resource. The fields contain such basic information as the title, subject, name of the creator, and a description. These fields also delve into details including rights, source, and format.
Qualified core level adds dimension and flexibility to the simple level of the Dublin core. This level can help to make the element set more specific and detailed. The qualified level may include information including rights holder, provenance, and audience. It is typically viewed as an enhancement to the standard 15 fields, rather than a base element.
The four primary goals of the Dublin core all focus on creating a widely-understood, simple systems to organize and describe resources. One important goal is that the element sets be easy to create and maintain, with a simple, effective design. It is also important that the terminology used in the elements is as universally understood as possible across nations and different professions. Another goal is to increase international involvement with the Dublin core by creating it in as many languages as possible. A final important goal of the Dublin core is to create a system of elements that, while remaining simple, can be endlessly extended to meet the needs of its users.
There are three Dublin core principles that can help creators to achieve the goals of the element set. The first, called the one-to-one principle, accepts that original creations and reproductions of material should be properly distinguished and that the proper authors for each should be acknowledged. The dumb-down principle essentially states that all values should be able to be used without qualifiers and that any qualifiers that exist are for the purposes of refinement and not for communicating base information. The final principle, appropriate values, acknowledges that information may be accessed by a human or a machine and should thus be presented so that it can be understood by both.