RESTful IDEAS

The technical documentation needed to operate and maintain an aircraft is supplied by several organizations including aircraft, engine, and component manufacturers. These manufacturers provide regular publications such as Aircraft Maintenance Manuals and Flight Operating Manuals as well as time-sensitive supplements such as Service Bulletins (SBs) and Temporary Revisions (TRs). Regulatory agencies like Transport Canada and the US Federal Aviation Administration (FAA) also publish technical information that affects the maintenance and operation of air vehicles and equipments. Examples are Advisory Circulars (ACs), Airworthiness Directives (ADs), and various forms and regulations.

The aerospace industry has adopted the S1000D technical publications standard. S1000D defines an XML vocabulary for technical publications and is based on the concepts of modularity, reuse, and metadata. While S1000D is the right payload, there is a need for a cost-effective, efficient, and massively scalable mechanism for aggregating and publishing up-to-date technical documentation to end users.

Approaches to interoperability based on a Service-Oriented Architecture (SOA) have traditionally relied on the web services standards stack including SOAP, WSDL, and UDDI. However, in today’s Web 2.0 world, alternative approaches such as the Representational State Transfer (REST) architectural style are getting a lot of attention for their simplicity, scalability, and rapid adoption. REST is based on the notion that resources on the web are URI-addressable and that all CRUD (Create, Retrieve, Update, and Delete) operations on those resources can be implemented through generic HTTP methods (e.g., HTTP GET, POST, PUT, DELETE).

The recently approved Atom Publishing Protocol (AtomPub) is a RESTful protocol supporting the description and discovery of collections of resources as well as creating, editing, and deleting those resources. Collections are represented as Atom Feeds. Resources are represented as Atom Entry documents. However these Atom entries are not limited to blogs, and can be any web resource including S1000D data modules and illustrations. OpenSearch 1.1 is a specification for describing the public interface of a search engine, URL templates for search requests, and the response formats (e.g., RSS 2.0 or Atom 1.0). Users can add search providers to their favorite web browsers using OpenSearch.

By exposing content repositories via OpenSearch, aerospace technical documentation users will be able to perform federated searches across repositories to obtain up-to-date technical information about a specific aircraft or equipment. The search results could be formatted in Atom to allow documentation users to receive updates via web feed.

In addition, AtomPub will enable the cross-platform remote access to library services to query, read, create, update, review, and delete content.

Finally, to ensure the high level of security needed in aviation operations, Atom Feed and Entry documents can be digitally signed or encrypted using the XML Signature and XML Encryption specifications respectively.