REST API Sample Clauses

REST API. In the following, we describe the REST API that exposes all resources on the Web and therefore completes our approach of an open workflow. RESTful APIs use resource URIs and allow an interaction with the resources using common HTTP requests, like GET to retrieve a representation of the resource, PUT (with existing URI) or PATCH to change a resource, PUT (with a new URI) or POST to create a new resource and DELETE to delete a resource. This usage of HTTP verbs is in accordance with the basic CRUD operations of a database and therefore especially suitable for data-centric applications. The basis for our API are the Linked Data principles, i.e., each and every resource that is created according to our ontology can be dereferenced (using GET) to retrieve an RDF representation. This representation contains all available links to other resources according to our ontology, sometimes with additional statements. A configuration, for example, contains not only links to assignments, but also further statements, which values are actually assigned to which parameter, i.e., the full configuration as it is supposed to be consumed by a Web service or a workflow. As workflows and Web services work very similarly in our system (workflows in fact are also Web services), we refer to them in the following as agents. There is also a third type of agent used in our system: Web services that store and provide resources like configurations or input files. To trigger actions in our system, messages have to be sent to an agent resource. As every information is represented in resources, it is only necessary to point to such a resource in order to submit it. If a new resource is to be created, its representation is sent via PUT or POST. The agents follow a combination of “follow your nose” and a few sensible defaults, i.e., careful deviations from hypertext-driven communication to reduce HTTP requests. In this vein, every GET on an agent returns its description, including its input and output parameters. By convention, appending /list on the root URI of the Web service lists all resources created by this service. This is especially needed for the storage services. In these cases, new data is added by POSTing the RDF description of a blank node that is skolemised3 3 Skolemization is the process of converting blank nodes into URI resources in such a way that their identity is preserved. and assigned a stable URI in the process. If no RDF resource is to be created, as for a file upload, ...