In this post we’ll discuss a diagram which captures a methodology for ontology development as an integrated approach. The diagram provides a high level view of how to conduct ontology development with maximum coverage and places the core idea of requirements management at the heart of it. The diagram draws from several strands of widely adopted methodologies as well as observation patterns made over several works in the area of applied ontology. It is to be noted that the diagram does not make any assumptions about the timescales involved for achieving each phase of the methodology. Furthermore, it is completely independent of any tools and subject area under study.
1. Goal and scope definition
This phase is regarded as the starting point of any ontology development cycle. It is largely a preparatory phase concerned with the identification of the domain and subject area being studied. It also lists the aims and objectives as well as the high level specifications, which not only guide the subsequent phases but are also later used for evaluating the degree of success of the ontology development activity. The scope of the ontology to be developed is defined in terms of its expected boundaries, coverage and assumptions. The Goal and Scope Definition phase may consider historical information available at hand to accelerate the ontology development process, such as existing ontologies and previous lessons learnt information. Overall, the high level view provided by this phase helps to encompass the requirements for the subsequent phases of the methodology.
2. Information gathering and elicitation
This phase helps to achieve a deeper understanding of the domain under study. Useful methods to conduct this phase are, for example, through workshops and interviews with subject matter experts, the analysis of existing content and the extraction of information from relevant media. Furthermore, because this phase helps raise further awareness of the domain under study, it is sometimes necessary to revise and refine the original Goal and Scope Definition phase. In the Information Gathering and Elicitation phase, it may be required to do some very early and rough-cut organisation of the gathered information, where no direct information structuring work is performed. It is also customary to consider emerging patterns in the way that certain concepts and ideas start to unfold.
3. Initial structuring
This phase is about making sense out of the gathered information and using information organisation methods for finding trends, rationalizing and structuring information. Methods used are, for instance, through collation of a term pool that captures concepts, short phrases and what they mean. Refinement of that information leads to finding out what works as potential classes, relations and logic for an ontology. Things like informal definitions of concepts, pseudo-logic and natural language descriptions are written down for subsequent review and use in ontology documentation. Moreover, it may be necessary to share and review the initial structures with both experts and non-experts. For that purpose, diagrammatic representations of the initial ontology structures are extremely handy.
This phase involves the use of a suitable ontology development environment (ontology editor, parser, rule engine, etc.) to encode, refine and test the initial structures as a formal model expressed in a chosen knowledge representation formalism. Classes, relations, logic, etc. are captured. Methods used to ensure that the formalization is correct are, for example, through partial instantiation of the ontology, classification, consistency and completeness checks, as well as other tests that are relevant to verifying the intended behaviour of the ontology structures.
This phase is concerned with ontology publishing and release as well as scaling into an ontology-driven system. In the Deployment phase, knowledge bases are built and any work necessary for fully instantiating, integrating and interfacing the ontology is performed and tested. This phase is primarily focused on proof of concept, roll-out of the ontology and user acceptance testing of an ontology-driven system.
This phase is where the evaluation of the developed ontology and its deployment is conducted. It requires looking back at the Goal and Scope Definition phase and assessing the extent to which the aims and objectives have been fulfilled and requirements met, in the context of the established scope. Several methods can be used for evaluation, where these fall broadly as qualitative and quantitative analysis methods. In the context of our integrated ontology development methodology we view ontology development as a knowledge management activity and for this reason, it is important to conduct, for example, lessons learnt reviews for continuous improvement purposes. This then feeds back into the Goal and Scope Definition phase as historical information to meet the needs of future ontology development cycles.
Requirements Management provides the ‘glue’ across all the phases of our integrated ontology development methodology. This not only ensures that things run according to plan but also promotes visibility throughout the whole methodology so that the inter-dependencies across phases are factored into the ontology development cycle. This way, it becomes possible to avoid an ‘over-the-wall’ approach but instead concentrate on ontology development as a concurrent activity where knowledge can be exploited collaboratively.