The Planetary Data System (PDS) has undertaken an effort to overhaul the PDS data architecture (e.g., data model, data structures, data dictionary, etc.) and deploy a software system (online data services, distributed data catalog, etc.) that fully embraces the PDS federation as an integrated system while leveraging modern information technology. A core component of this new system is the Registry Service that will provide functionality for tracking, auditing, locating, and maintaining artifacts within the system. These artifacts can range from data files and label files, schemas, dictionary definitions for objects and elements, documents, services, etc.
Registries are pervasive components in most information systems. For example, data dictionaries, service registries, LDAP (Lightweight Directory Access Protocol) directory services, and even databases provide registry-like services. These all include an account of informational items that are used in large-scale information systems ranging from data values, such as names and codes, to vocabularies, services, and software components. The problem is that many of these registry-like services were designed with their own data models associated with the type of artifact they track, and they each have their own specific interface for interacting with the service.
This Registry Service implements the data model specified in the ebXML Registry Information Model (RIM) specification that supports the various artifacts above, as well as offering the flexibility to support customer-defined artifacts. The Registry Service provides a generalized track and locate function for registered artifacts within the system. Services and individual actors within the system interact with the registry to inform the service about new managed artifacts or to look up/update basic information about existing registered artifacts.
One of the unique features of the Registry Service is the REST-based external interface that is accessible via the Hypertext Transfer Protocol (HTTP). REST (Representational State Transfer) is a style of software architecture.
Another unique feature of the Registry Service is model-based configuration. The ebXML specification defines a registry configuration file that configures the registry for user-defined artifacts. The PDS4 data model is designed specifically to take advantage of this feature, and defines attributes that the registry requires for artifact identification, association, and search. Non-PDS deployments of the Registry Service should have a companion data model to make use of this feature.
The Registry Service has been in operation for the PDS project since April 2013 as the core component of the PDS data management system supporting PDS Version 4. Though the software, as deployed, satisfies the original requirements, it is anticipated that future enhancements will be made as the PDS system matures.
This work was done by Sean H. Hardman, Paul M. Ramirez, John S. Hughes, Ronald Joyner, Michael D. Cayanan, Hyun H. Lee, and Daniel J. Crichton of Caltech for NASA’s Jet Propulsion Laboratory.