[x3d-public] improved definitions, clarifications to X3D Architecture Clause 3 Terms, definitions, acronyms, and abbreviations

[Brutzman, Donald (Don) (CIV)]

We are considering Mantis 1173 to add a number of definitions and clarifications to the X3D Architecture specification.  This was first proposed in September 2017.


  *   Mantis 1173: Clause 3 Terms, definitions, acronyms, and abbreviations - Definition of node and statement are insufficient
  *   https://www.web3d.org/member-only/mantis/view.php?id=1173

Review and any suggested wording improvements are welcome.  Absent objects or improvements, we will apply these nonfunctional editorial changes.

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Subject: Abstract specification definitions of node and statement are insufficient.

Problem: the abstract specification does not provide clear definitions for nodes and statements, resulting in ambiguous distinctions throughout other sections.

The current definition for node is vague:
"3.1.47 node, fundamental component of a scene graph"

Suggested definition, improvements welcome:
"3.1.47 node, fundamental component of a scene graph that defines information regarding animation, display, geometry, graph structure, interaction, object metadata, or rendering. Nodes are not statements.

No definition for statement is provided. Suggested:
"3.1.70.5, statement, fundamental component of a scene graph that defines document information, version/profile/component support, routing, and other scene-related information. Statements are not nodes.

Existing usage of note:
"3.1.87 X3D file, set of X3D nodes and statements as defined in this part of ISO/IEC 19775"

Further action needed: Core component defines multiple capabilities requiring X3D statement support. Recommend that support for all X3D statements is included as a requirement in Core component, both in prose and in support table. For example: "All X3D statements are defined as part of Core component level 1."

Table 7.2 - Core component support levels
http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/core.html#t-Coresupportlevels
Can add similar table entry "All X3D statements are defined as part of Core component level 1."

Correction needed:
Figure 4.1 - X3D architecture
http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/concepts.html#f-X3DArchitecture
"The abstract structure of the sequence of statements that form an X3D world is specified in 7.2.5 Abstract X3D structure."
should be modified to read "sequence of nodes and statements that form an X3D world"

7.2.5 Abstract X3D structure
http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/core.html#AbstractX3DStructure
7.2.5.1 Organization
should similarly modify
"An X3D world is conceptually defined as a sequence of statements organized conceptually as a file."
to say "as a sequence of nodes and statements"

Needed:
"PROTO instances are nodes."

Suggested:
"Comments are neither nodes nor statements."

This section should also include a paragraph that lists X3D statements, such as
"X3D statements include X3D, HEAD, PROFILE, COMPONENT, META, UNIT, Scene, ROUTE, PROTO declare, EXTERNPROTO delare, PROTO interface, PROTO body, field, fieldValue, IS, connect, IMPORT, EXPORT. Syntax and explicit/implicit definition for these statements can vary among various encodings and language bindings."

Further review of the abstract specification is warranted to see if other clarifications and corrections are needed.

Of note is that clear distinction of nodes and statements is also necessary for proper specification of the X3D Unified Object Model.

These clarifications are not expected to break any existing X3D model content because the existing legacy specification makes no relevant restrictions on use of X3D statements. Similarly, these clarifications do not require changes (but may inspire improvements) to existing X3D implementations.
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all the best, Don
--
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu<mailto:brutzman at nps.edu>
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman

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