2.7 Representation of process knowledge
2.7.2 Process Modelling in Ontology Engineering
In what follows we investigate how the notion of process has been tackled in ontology engineering. By doing that, we omit to report how the notion has been modelled in knowledge engineering, under the assumption that the relevant approaches converged in the way ontology engineering tackled the problem. Moreover, we will omit the ontologies specifically about Semantic Web Services and Provenance, because these two themes have dedicated sections in this chapter.
As introduced in Section 2.2, an ontology is an “explicit specification of a conceptualisa- tion” [Gruber (1991)]. In many cases, the term “ontology” can be associated to conceptual analysis and domain modelling, when this is accompanied by a rigorous methodology. One of the peculiari- ties of ontologies with respect to other types of models is the multidisciplinary approach, where logic, linguistics and cognition play a crucial role in expressing the structure of reality, often at a high degree of abstraction [Guarino et al. (1998)]. Ontologists characterised the discipline as an approach to ground logical theories on fundamental a priori distinctions about the nature of reality, for example, the ones between physical, objects, events, and processes [Guarino (1994)].
The Common Process Ontology (CPO) [Polyak and Tate (1998)] was developed by surveying existing standards, including the ALPS language for process specification [Catron and Ray (1991)], the Process Interchange Format (PIF) [Lee et al. (1996)], the Workow Reference Model (of the Workflow Management Coalition) [Hollingsworth and Hampshire (1995)], and the Shared Plan- ning and Activity Representation (SPAR) [Tate (1998)]59. The objective was to find a common ontology of processes which offer the fundamental concepts and terminology for the expression of process knowledge. CPO is modelled in three parts: a meta-ontology, an object ontology, and the constraint ontology. In CPO, a process provides a specification of behaviour delimited by a pair of begin/end time points, limiting the definition of behaviour as “something that one or more agents perform” [Polyak and Tate (1998)].
With few exceptions, ontology engineering is mostly concerned with developing an ontologically 59See also [Knutilla et al. (1998)] for a survey on process modelling of that time.
grounded definition of Process more than giving a tool to actually model and express concrete processes (for examples, see foundational ontologies like SUMO [Niles and Pease (2001)]). The APT framework introduces the concept of free process by means of five principal dimensions: homomerity pattern, participant structure, dynamic composition, dynamic shape, and dynamic context[Seibt (2001)].
The Process Specification Language (PSL) [Gruninger and Menzel (2003)] and ontology [Grüninger (2004)] axiomatizes a set of semantic primitives useful for describing manufacturing processes. PSL distinguishes between Activity (as class of actions), Activity-occurrence (as instance), Timepoint, and Object (anything else). A Fundamental Business Process Modelling Language (FBPML) has been proposed [Chen-Burger et al. (2002)] to fill the gap between high-level Enterprise Models (EM) and Software System Development through mediator languages such IDEF3 [Maker et al. (1992)] and PSL.
Projects like SUPER60produced a set of ontologies for Semantic Business Process Management (SBPM), mostly developed in WSML [De Bruijn et al. (2006)] or OCML [Motta (1998)].
DOLCE (Descriptive Ontology for Linguistic and Cognitive Engineering) was developed in the context of the WonderWeb project61 with the purpose of capturing the conceptual categories underlying human common sense through and language [Gangemi et al. (2002); Masolo et al. (2003)]. Several approaches targeted to the conceptualisation of processes originated from DOLCE. DnS (Descriptions and Situations) provides a framework for representing contexts, methods, norms, theories, situations, and models at first-order, thus allowing a partial specification of those entities. Applying a constructivist approach, it allows designing contextualised models using the types and relations defined by other foundational ontologies (or ground vocabularies) [Gangemi and Mika (2003)]. For example, in the DOLCE+DnS Plan Ontology (DDPO), DOLCE and DnS are used together to construct a Plan Ontology that includes both physical and non-physical objects, for example, events, states, regions, qualities, contextualised in situations. As a result, DDPO can define and regulate types of actions, their sequencing, and the controls performed on them [Gangemi et al. (2004)]. The ACL Process Ontology was developed to propose an agent-based approach to Semantic Web Services [Gibbins et al. (2004)]. Semantic Business Process Management (SBPM) is an attempt to apply ontology engineering to combine the requirements of governance in large businesses with the one of human interaction and automation [Hepp et al. (2005); Hepp and Roman (2007)]. Ontology Design Patterns (ODP) emerged to focus the development of ontologies in the Semantic Web on reusable, modular, interlinked libraries of components [Gangemi (2005); Gangemi et al. (2007)]. Many of these patterns are directly or indirectly derived from DOLCE.
60SUPER: http://kmi.open.ac.uk/projects/name/SUPER
2.7. REPRESENTATION OF PROCESS KNOWLEDGE 73 Extreme Design (XD) offers a methodological framework for the application of ODPs in ontology development [Presutti et al. (2009)]. Part of this effort was the development of a catalogue of Content Patterns(CP) [Daga et al. (2008)], generic reusable components to be used with by specialization (following the XD methodology), or as templates [Hammar and Presutti (2016)]. Content Patterns are often defined by combining and expanding other CPs. This is a (non-comprehensive) list of ontology patterns that can be adopted in process modelling:
– Action. The purpose of the pattern is to model actions that can be proposed or planned and performed or abandoned, including a specification of their status and durations in time62. – AgentRole. This pattern permits to make assertions on roles played by agents63.
– Role task. Designed to connect intensional descriptions of actions (tasks) with objects (roles)64.
– BasicPlan represents plans descriptions and their executions. The expansion involves the partial clone of ontology elements from DOLCE Ultra Lite and Plans Lite ontologies65. – BasicPlanExecution has the purpose of representing executions of plans along with the entity
that participates in such an execution. This CP is composed of other CPs, namely Situation and Region66.
– Reaction combines a number of CPs to model temporal events, for instance tracing agents and actions they produce, events that are results of some action(s), including the interpretation of dependency between actions as reactions67.
The effort of the ontology engineering community on building high-quality knowledge models for the Semantic Web impacted several domains, within and outside computer science. The research mentioned above had a particular impact in the area of Semantic Web Services (SWS), which we survey in the next Section.