1. A method for creating a virtual personal assistant (“VPA”) computer application for a domain of interest, the method comprising, with a computing system: determining the domain of interest; accessing a computerized ontology defining a structure for representing knowledge relating to a plurality of domains including the domain of interest, each domain referring to a category of information and/or activities in relation to which the VPA computer application may conduct a conversational natural language dialog with a computing device user, the ontology having linked thereto a plurality of re-usable VPA components, each of the re-usable VPA components being accessible by an executable VPA engine to, during operation of the VPA, determine a likely intended goal of the computing device user based on a determined meaning of explicit and implicit conversational natural language input of the computing device user, execute a task on behalf of the computing device user, and/or generate a likely appropriate system output in response to the conversational natural language input; determining a data relationship between the domain of interest and at least a portion of the ontology; and suggesting a re-usable VPA component to use to create the VPA computer application for the domain of interest based on the data relationship between the domain of interest and the ontology.