SCUFL2 is the new (since Taverna 3) mechanism for specifying Taverna workflows. SCUFL2 defines a model, a workflow bundle file format (.wfbundle), and a Java API for working with workflow structures. SCUFL2 is the workflow language for Taverna 3, and replaces Taverna 2's t2flow format.
Summary¶
SCUFL2 is the Taverna 3 mechanism for specifying Taverna workflows. SCUFL2 adopts Linked Data technology and preservation methodologies to create a platform-independent workflow language that can be inspected, modified, created and executed.
SCUFL2 comes with a Java API that can be used for programmatic access to read and write SCUFL2 workflow bundles.
A workflow bundle is a structured ZIP file with the workflow definitions included as XML documents. Those workflow documents are described by an XML Schema and are also valid RDF/XML. The XML Schema allows tools to read and write SCUFL2 workflow definitions as regular structured XML. The RDF allows RDF-enabled tools to link workflow definitions with external resources.
The workflow structure is defined using an OWL ontology and annotated with URIs so that third parties can form semantic statements about any component of a Scufl2 workflow, for example to state that a particular service produces outputs of a certain type, or that a data link was added by a specific researcher.
Semantic annotations and a manifest for the bundle declare the purpose of, and links between the different components forming a workflow. This allows third parties to extract and append annotations about data and services used by the workflow.
Motivation¶
The t2flow serialization format suffers from being very close to the Java object model, and contains various items that are simply Java beans serialized using XMLBeans. As the t2flow format is very verbose, it can be difficult to deal with for third party software to do inspection ("Which services does this workflow use?"), modification ("Change all calls to broken.com to fixed.com") and generation ("Build a custom workflow from a button").
Developers have informed us that the old SCUFL format of Taverna 1 was significantly easier to work with. However, this format also has its caveats, like no schema, unidentified ways to extend service definitions for Taverna plugins and not supporting various new features in the Taverna 2 engine.
We have therefore decided to form a new serialisation format for workflows, called SCUFL2.
Overview¶
SCUFL2 consists of:
- SCUFL2 language
- SCUFL2 Workflow Bundle format
- SCUFL2 API for Java