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On Jan 27, 2017 3:37 PM, "Denenberg, Ray" <[log in to unmask]> wrote:

 In 1.0, titles applied only to Works and Instances.  Subject and creators applied only to Works.  What we found was that for some (admittedly rare) cases, title, creator, and subject could apply at the Item level.

Were there some sorts of common characteristics for these various  unexpected cases. For example, when does an item gain a title? Is this for things like the various individual copies of the Gutenberg Bible, or is it some other situation? 

 Complexity of constructed classes 

This might not be as complicated as it seems (or I may have gazed too long into the abyss, which is making it feel uncomfortable). 

Let’s say you want to restrict titles to Works, Instances, and Items, by imposing a domain on property bf:title.   You can do that in a number of ways, including constructed or artificial classes.  We decided that the benefit of doing this is not worth the cost of the added complexity this would impose.

In Manchester Syntax [1], 

ObjectProperty: bf:title
   Domain: bf:Work or bf:Instance or: bf:Item 

As another example consider property hasEquivalent. A Work can be equivalent to another Work, an Instance to an Instance, or an Item to an Item. But a Work cannot be equivalent to an Instance, or an Instance to an Item, etc. In other words, the resource type of the subject (Work, Instance, or Item) must be the same as the resource type of the object.  This would be a logical constraint to impose, if it could be imposed in a sensible manner.   But it cannot, and so the range of hasEquivalent is unconstrained.


Class: bf:Work
    SubClassOf: bf:hasEquivalent only bf:Work

Class: bf:Instance
    SubClassOf: bf:hasEquivalent only bf:Instance

Class: bf:Item
    SubClassOf: bf:hasEquivalent only bf:Item

[ also, 

DisjointClasses: bf:Work, bf:Instance, bf:Item 

ObjectProperty: bf:hasEquivalent 
        Characteristics: Symmetric, Reflexive, Transitive
        Domain: bf:Work or bf:Instance or bf:Item 
]


Simon 

[1] OWL 2 Web Ontology Manchester Syntax (Second Edition).   https://www.w3.org/TR/owl2-manchester-syntax/