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The WDO approach

Ontologies are developed for several purposes including the support for search, information integration and services discovery. At the same time, organizations developing ontologies are also using workflow techniques to support the computation of complex activities. Workflow-driven ontology (WDO) is a new approach for ontology design. Typically, use cases are used to drive the design of ontologies. In the WDO approach, the elicitation and connection of concepts required to specify abstract workflow specifications are used to drive the design of ontologies. We claim that these abstract workflow specifications are indeed the use cases for WDOs. For instance, in the context of a WDO, if a concept is defined as a kind-of data, it must be either the input to or output of some concept defined as a kind-of method. In this case, both data and method are core concepts of WDOs.

Due to the very nature of the process of designing WDOs, they provide an intentional support to workflow development. WDOs can capture knowledge as any other ontology; however, they offer an additional benefit: by using workflow specifications derived from WDOs, domain experts can validate specifications of key concepts within WDOs.

The WDO metamodel

The current implementation of the WDO metamodel is rooted in the OWL concept Thing. The class WDOConcept represents the most general WDO class, and the model is then divided into two main hierarchies; the hierarchy rooted in WFSequenceElement contains classes that are used in the construction of workflow specifications; the hierarchy rooted in Data contains classes that are used to capture data concepts of the scientific domain of interest as well as classes used to compose complex data constructs that are used in the generation process of workflow specifications; these complex data constructs are referred to as Composite Data.

The Method class in the WDO metamodel is used to capture the functionality of the scientific domain of interest, i.e., services or algorithms. With respect to workflow specifications, the methods represent units of work in the workflow. In other words, a workflow can be viewed as the composition of several methods, where the input of a method either comes from a human user or from the output of a previously executed method according to an ordering specified by the workflow specification. The end result of the workflow specification is the output of the method that executes last.

WDO implementation

WDO is being implemented as two projects, the WDO API and the WDO-It! application. The WDO API builds on top of the Jena Semantic Web Framework that provides a programmatic environment for OWL, and includes a rule-based inference engine. The WDO API provides functionality to generate workflow-driven OWL ontologies, including the creation of WDO-specific concepts and relationships, as well as functionality to generate model-based workflow specifications.

WDO-It! is an application that is intended to target scientist users. Its user interface enables users to capture scientific process knowledge in an OWL ontology, generate workflow specifications from such process knowledge, and assess the quality of the captured process knowledge. WDO-It! also provides a graphical representation of the workflow specifications generated from the process domain knowledge.

The concept brainstorm tab

The relationship elicitation tab

The workflow generation tab