I agree with everything in this paper. I would add:


Although abstracts, there are some engineering principles for developing ontologies. As a matter of fact there are several methodologies for developing ontologies. Most of them, if not all, follow in one way or another these principles. However, very few of them do mention the need for a singular “view” of the world, on the contrary, methodologies tend to embrace ontological pluralism.

First design principle: “The conceptualization should be specified at the knowledge level without depending on a particular symbol-level encoding.”
Second design principle: “Since ontological commitment is based on the consistent use of the vocabulary, ontological commitment can be minimised by specifying the weakest theory and defining only those terms that are essential to the communication of knowledge consistent with the theory.”
Third design principle: “An ontology should communicate effectively the intended meaning of defined terms. Definitions should be objective. Definitions can be stated on formal axioms, and a complete definition (defined by necessary and sufficient conditions) is preferred over a partial definition. All definitions should be documented with natural language.”
Fourth principle: “An ontology should be coherent: that is, it should sanction inferences that are consistent with de definitions. […] If a sentence that can be inferred from the axioms contradicts a definition or example given informally, then the ontology is inconsistent.”
Noy and McGuinness’s first guideline: “The ontology should not contain all the possible
information about the domain: you do not need to specialise (or generalise) more than you need for your application.”
Noy and McGuinness’s second guideline: “subconcepts of a concept usually i) have
additional relations that the superconcetp does not have, or ii) restrictions different from these of superconcepts, or iii) participate indifferent relationships than supperconcepts. In other words, we introduce a new concept in the hierarchy usually only when there is something that we can say about this concept that we cannot say about the superconcept. As an exception, concepts in terminological hierarchies do not have to introduce new relations”.
Noy and McGuinness’s third guideline: “If a distinction is important in the domain and we
think of the objects with different values for the distinction as different kinds of objects, then we should create a new concept for the distinction”.
Noy and McGuinness’s fourth guideline: “A concept to which an individual instance belongs should not change often”.

As for the several definitions of ontologies I would say:
“An ontology is a non-necessarily complete, formal classification of types of information structured
by relationships defined by the vocabulary of the domain of knowledge and by the canonical
formulations of its theories”

Guarino and Smith heavily influence this definition. It complies with Guarino in that an
ontology is, possibly, an incomplete agreement about a conceptualisation and not a
specification of the conceptualisation. Ontologies should therefore be understood as
agreements amongst people within a community sharing interest in a common domain. By
“incomplete” it is understood that the classification of types of information should be left
open for interoperability purposes. By “formal” it is meant that the ontology specification can
be easily translated into a machine-readable code, as the ontology should support inference
processes within those information systems using it. However, it should be noted, that the
latter is not mandatory when defining ontologies on an abstract level.

More on this on my PhD thesis http://www.alexandergarci...