PID service - an advanced persistent identifier management service for the semantic web

Abstract

Persistent identifiers are an integral part of the Semantic Web and Linked Data applications: they enable the stable identification of digital objects and may be used as a top-level application programming interface (API) to bind multiple representations of digital objects into a single, coherent, data model. In addition to these technical tasks, persistent identifiers and their management are of prime concern for the governance of Domain Name System (DNS)-based domains containing output from multiple parties that need to ensure identifier uniqueness as their first order of operation. Our contribution to solutions for the technical and governance challenges posed by identity management is the PID Service - a persistent identity service - which is a web service offering advanced persistent identifier management with features not found in proxy servers and other web redirection products. The PID Service is able to store and implement large numbers of complex Uniform Resource Indicator (URI) redirection rules and handle related sets of rules according to rule hierarchies. This, combined with a web-based graphical user interface and database rule storage, allows users of the PID Service to far more easily manage large numbers of complex rules within a domain avoiding rule collision and specialised partial URI delegation. The Application Programming Interface allows programmatic access to all features of the service that, in turn, provides boundless integration possibilities with other applications and services. These possibilities include, but are not limited to, applications such as automatic data harvesting and digital entity identification. The PID Service is being used for a number of operational Semantic Web and Linked Data applications including the 'environment' portion of the Australian Commonwealth Government's data.gov.au project operating at environment.data.gov.au. There the PID Service handles the identifiers for a range of Linked Data products including the large and complex national Australian Hydrological Geospatial Fabric. In addition to handling current products within the domain, the design of the PID Service is such that it will be able to cope with large increases in number of persistent identifiers, which is important given the rising popularity of open government data and the use of services such as environment.data.gov.au. The PID Service has also formed part of the key service infrastructure in the Spatial Identifier Reference Framework (SIRF) (Atkinson et al., 2013) - a scalable linked data infrastructure that aims to improve the supply of open, spatially enabled and linked information. SIRF provides means to reliably cross-reference identifiers for the real-world locations and encodes spatial relationships between features (i.e. containment and adjacency). This framework of spatial identifiers is used to link together information (e.g., socio-economic statistics) about locations, stored in multiple distributed systems. In this paper we outline the motivation for the PID Service including the limitations of other proxy and redirect technologies. We provide an overview of the system design and describe both its technical functionalities and use cases. Finally, we describe the aforementioned installation of the PID Service at environment.data.gov.au and discuss how it impacts domain governance.