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   Re: Grooves: why are "data" designed as properties and not nodes ?

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  • From: "Steven R. Newcomb" <srn@techno.com>
  • To: xml-dev@ic.ac.uk
  • Date: Fri, 24 Sep 1999 13:53:52 -0500

[Anders W. Tell:]
> Like many others have I started to look at the Grooves model once
> more and this time at little closer. Im especially interested in how
> my current "DOM-compliant" model matches the Groove.

A couple of remarks:

* It's "grove", not "groove".  It's (kind of) an acronym: Graph
  Representation Of property ValuEs.

* The SGML Property Set, which is an instance of a property set as
  defined by the grove paradigm, is somewhat comparable to the DOM.
  The DOM is not directly comparable to the grove paradigm.  Maybe
  your current "DOM-compliant" model is comparable to the grove
  paradigm, though (depending on what it is).

> One aspect got my attention and it was that properties and not nodes
> contains "data" such as strings,integer,etc.

> Could somone explain the design rationale why properties and not node
> carries data ?

Properties do not "contain" data.  Properties are like variables: they
can "have" values.

A node *consists* of a set of named properties and their values, if
any.  A node (an instance of a class of nodes) can have many
properties.  Some properties are "data" properties; this means that,
unlike "nodal" properties, their values must be data, and cannot be
nodes.  If nodes were the same thing as data, or if nodes could be
treated as data, then they would have only one property, whose value
would be the data.  That would not be as useful as having nodes
consisting of any number of named properties, any number of which can
be data properties.

> Does this design imply that tree-algorithms are easier to implement ?

The design of the grove paradigm is explicitly intended not to imply
anything at all about implementation.


Steven R. Newcomb, President, TechnoTeacher, Inc.
srn@techno.com  http://www.techno.com  ftp.techno.com

voice: +1 972 231 4098
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