C.1 Topics and introduction

C.1.1 Topics

This annex provides a detailed description of the grammar for each syntactic element in this part of ISO/IEC 19776. Table C.1 lists the topics in this clause:

Table C.1 — Topics in this clause

C.1 Table of contents and introduction
C.1.1 Topics
C.1.2 Introduction
C.2 X3D XML Schematron

C.1.2 Introduction

XML Schematron [I19757-3] is a language for making assertions about the presence or absence of patterns in linked XML documents. If assertions for correct behavior fail, then error and warning messages are provided.

X3D XML Schematron checks the syntax of an X3D scene expressed in XML form, in particular verifying correct values and dependency relationships among attribute values. It is designed to complement the expressive power of X3D XML Document Type Definition (DTD) and X3D XML Schema.

The X3D XML Schematron is defined by an XML tagset using an XML-based grammar as specified in [SCHEMATRON.1] [SCHEMATRON.2].

While not fully exhaustive in nature, the X3D XML Schematron typically has sufficient expressive power to:

Ensure that well-formed XML requirements are met in accordance with [XML],
Confirm satisfactory structure X3D models that may include any or all aspects of the functionality specified in Part 1 of ISO/IEC 19775,
Validate correct naming and usage of elements (i.e., X3D nodes),
Identify correct naming of corresponding attributes (i.e., simple-type X3D fields),
Validate correct types and ranges of attribute values, typically in great detail,
Confirm correct spelling and capitalization of enumeration values defined in Geopspatial, HumanoidAnimation, and other components,
Check each of the Interpolator nodes to confirm that key and keyValue arrays shall have the same length,
Determine whether a DEF value appears before corresponding a USE value., and
Perform a diverse variety of tests that check for internal consistency and Quality Assurance (QA).

Editors note: adding explanatory excerpts from X3D XML Schematron source seems like unnecessary detail.

Current versions of X3D XML Schematron files are maintained at [X3DSCHEMATRON].

Additional capabilities for validation of field values are provided by XML Document Type Definition (DTD), XML Schema, and X3D Regular Expressions (regexes) [X3DREGEX].

NOTE Additional information about X3D XML scene structure, allowed field values, data type restrictions, authoring hints, warnings, and errors can be found in X3D Tooltips [X3DTOOLTIPS] and X3D Unified Object Model [X3DUOM]. Validation assets are maintained in human-readable and machine-readable forms, in version control, and with corresponding documentation at [X3DVALIDATION].

C.2 X3D XML Schematron

X3dSchematronValidityChecks.sch is the X3D XML Schematron file that validates model correctness for X3D versions 3.0, 3.1, 3.2, 3.3, and 4.0 content.

Editors note: copying source document excerpts here seems superfluous.

<!-- for readability, source document (6500 lines) not included -->