Re: [xml-dev] RE: When you create a markup language, what do yourparent

[Michael Kay <mike@saxonica.com>]

I think most examples of parent-child relationships fall into one of 
three categories:

(a) representing the properties of an object

<book>
<price>3.25</price>
</book>

(b) representing a one-to-many relationship (often a "containment" or 
"aggregation" relationship, though in my experience data modellers do 
not use those terms consistently)

<county name="Berkshire">
<town name="Windsor"/>
<town name="Reading"/>
</county>

(c) representing a many-to-many relationship with the help of link elements:

<xs:attribute-group name="G">
<xs:attribute ref="A"/>
<xs:attribute ref="B"/>
</xs:attribute-group>

(represents a many-to-many relationship between attribute groups and 
attributes).

In each case there are other choices available to the schema designer, 
and different designers will quite legitimately make different choices; 
there are no "normalization rules" governing XML schema design as there 
are in relational databases. A good schema design will however exhibit 
some internal consistency.

Document modelling is of course rather different from data modelling. 
With document-oriented models, the parent-child relationship usually 
reflects a textual containment hierarchy that corresponds to the 
abstracted structure of a rendition of the document.

Michael Kay
Saxonica


On 26/09/2011 23:49, Costello, Roger L. wrote:
> Hi Folks,
>
> These two markup languages have a consistent definition of what parent elements and child elements mean:
>
> 1. RDF
> 2. GML
>
> Both languages specify that parent elements represent a resource or object and child elements represent properties or attributes.
>
> Are those the only markup languages that have a consistent definition of what parent elements and child elements mean?
>
> If one is creating a markup language and wants to adopt a consistent definition for parent elements and child elements, is resource/object and property/attribute the only way to accomplish it?
>
> Is an Object-Oriented approach to markup the only viable approach when one wants to have a consistent definition for parent elements and child elements? That would be quite astonishing, given that people such as Tim Bray argue that "XML is 180 degrees apart from OO".
>
> /Roger
>
>
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