The technologies described here meet a need first recognized, albeit dimly, two decades ago. Rewind to circa 2000, when the parallel development of two W3C specifications, XML Schema and RDF Schema, both called “schema languages” but with radically different uses, caused some confusion.
This confusion permeated our early discussions about the Dublin Core. Was it an XML format, an RDF vocabulary, or somehow both? Could metadata just follow arbitrary formats or did it need a data model? In 2000, the Dublin Core community turned to “application profiles” as a way to mix and match multiple vocabularies to meet specific needs, and the idea was an instant hit even if people disagreed about their use. Were they more for validating data, or more about finding rough consensus on a metadata model within a community of practice? Attempts to bridge the XML and RDF mindsets in the DCMI community, notably with a Description Set Profile constraint language for validating RDF-based metadata (2008), never quite caught on. Perhaps the idea needed a bigger push?
Fast-forward to 2013, when W3C convened a workshop on RDF validation which revealed that many communities had been circling around the same issues, and which ultimately led to the results described here . This book focuses on data validation, an addition to the Semantic Web stack that is long overdue. But from a DCMI perspective, the ideas for future work outlined in its Conclusion are just as exciting: the prospect of using ShEx- or SHACL-based application profiles to map and convert between data models, size up aggregated datasets, or provide nuanced feedback to data providers on quality issues. ShEx and SHACL, finally production-ready, are full of potential for further evolution.
Tom Baker, Dublin Core Metadata Initiative