Re: Definitions

Hi Mark,

This seems like a useful attempt to clarify some terminology. 

A couple of quick comments.

First, the notion of "constraint schemas" may need a clearer definition. This is
arguably as much an aspect of the processing model for how the schema is used,
rather than an intrinsic property of the schema. For example, the OWL
cardinality restrictions can be thought of as constraints or as the basis for
inference. If a class has minCardinality 1 on some property, and in my dataset
there isn't one, then depending on my processing model I can either infer the
existence of some blank node representing that value or I can complain that a
value is missing. 

I do agree that this is an important aspect of schemas to capture though. The
web ontology languages are relatively weak, compared to something like UML, at
expressing constraints.

Second, it would be worth clarifying that the same schema in the same language
can express all of these facets. I'm sure you realize this but the phasing could
be mis-read as suggesting that schemas tend to be one or other of these flavours
- whereas your average OWL ontology often has all four facets.

Third, some tweaks to the name you've chosen might we worth considering. For
example, your description of "conceptual schema" could be called a "vocabulary",
which would help to distinguish it from normal usage of things like "conceptual
model" which are much closer to your "ontological schemas". Similarly, you could
simply call "ontological schema" an "ontology".

Cheers,
Dave

"Butler, Mark" wrote:
> 
> Hi team,
> 
> One of the problems with this are is that terms like schema and ontology are
> used in multiple, conflicting ways. John and myself would look to propose
> some specific terms in order to distinguish between these conflicting
> definitions, but I'd be interested in comments on these definitions from the
> team:
> 
> Instance data: Instance data is metadata that is specific to resources.
> 
> Schemas: Schemas are generic descriptions of collections of metadata. This
> report proposes that it is possible to distinguish between four different
> types of schemas: conceptual, ontological and constraint schemas and
> controlled vocabularies. In the Semantic Web specific schema information,
> possibly composed of all four types of schema, is identified using a
> namespace.
> 
> Conceptual schemas:  A conceptual schema defines a set of classes and
> properties that can be used to describe a particular domain.
> 
> Ontological schemas: Ontological schemas describe relationships between
> classes and properties, both within a namespace and between multiple
> namespaces.
> 
> Constraint schemas: A constraint schema describes constraints that are
> applied to classes and properties. The main use of constraint schemas is to
> validate metadata associated with a particular schema.
> 
> Controlled vocabularies: A controlled vocabulary defines a set of terms that
> may be used as property values. The controlled vocabulary may optionally
> define relations between the terms such as synonyms.
> 
> Namespace: A namespace is grouping of related information that uses a common
> name. A namespace may provide no information at all, but ideally it will
> provide a conceptual schema, optionally supported by an ontological schema,
> a constraint schema and optionally one or more controlled vocabularies.
> 
> Application profile: An application profile is a conceptual schema derived
> from subsets of several other conceptual schemas and associated with a
> particular application.
> 
> thanks in advance,
> 
> Dr Mark H. Butler
> Research Scientist                HP Labs Bristol
> mark-h_butler@hp.com
> Internet: http://www-uk.hpl.hp.com/people/marbut/

Received on Thursday, 28 August 2003 14:15:03 UTC