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7.1 Introduction

7.2 Conformance

7.3 Minimum support requirements

7.1 Introduction

7.1.1 Objectives

This clause provides rules for identifying conforming generators and interpreters of ISO/IEC 14772 along with specifications as to the minimum level of complexity which must be supported.

The primary objectives of these rules are:

1. to promote interoperability by eliminating arbitrary subsets of, or extensions to, ISO/IEC 14772;
2. to promote uniformity in the development of conformance tests;
3. to facilitate automated test generation.

7.1.2 Scope

This clause provides conformance criteria for metafiles, metafile generators, and metafile interpreters.

This clause addresses the VRML data stream and implementation requirements. Implementation requirements address the latitude allowed by VRML generators and interpreters. This clause does not directly address the environmental, performance, or resource requirements of the generator or interpreter.

This clause does not define the application requirements or dictate application functional content within a VRML file.

The scope of this clause is limited to rules for the open interchange of VRML content.

7.2 Conformance

7.2.1 Conformance of metafiles

Conformance of metafiles to ISO/IEC 14772 is defined in terms of the functionality and form specified in Part 1. In order to conform to ISO/IEC 14772, a metafile shall be a syntactically correct metafile.

A metafile is a syntactically correct version of ISO/IEC 14772 if the following conditions are met:

1. The metafile contains as its first element a VRML header comment node;
2. All nodes contained therein match the functional specification of the corresponding nodes of ISO/IEC 14772-1. The metafile shall obey the relationships defined in the formal grammar and all other syntactic requirements.
3. The sequence of nodes in the metafile obeys the relationships specified in ISO/IEC 14772-1 producing the structure specified in ISO/IEC 14772-1. For example, ...
4. No nodes appear in the metafile other than those specified in ISO/IEC 14772-1 unless required for the encoding technique. All nodes not defined in ISO/IEC 14772-1 are encoded using the PROTO or EXTERNPROTO nodes.
5. The metafile is encoded according to the rules in the standard clear text encoding in ISO/IEC 14772-1 or such other encodings that are standardized.

7.2.2 Conformance of metafile generators

Conformance of metafile generators is defined in terms of conformance to the functionality defined in ISO/IEC 14772-1. A metafile generator which conforms to ISO/IEC 14772 shall:

1. generate no syntax in violation of ISO/IEC 14772;
2. generate metafiles which conform to ISO/IEC 14772;
3. map the graphical characteristics of application pictures onto a set of VRML nodes which define those pictures within the latitude allowed in ISO/IEC 14772.

7.2.3 Conformance of metafile interpreters

Conformance of metafile interpreters is defined in terms of the functionality in ISO/IEC 14772. A metafile interpreter which conforms to ISO/IEC 14772 shall:

1. be able to read any metafile which conforms to ISO/IEC 14772;
2. render the graphical characteristics of the VRML nodes in any such metafile into a graphical image or picture within the latitude defined in ISO/IEC 14772.

7.3 Minimum support requirements

7.3.1 Minimum support requirements for generators

There is no minimum complexity which must be supported by a conforming VRML generator except that the file must contain the required VRML header. Any compliant set of nodes may be generated of arbitrary complexity.

7.3.2 Minimum support requirements for interpreters

This subclause defines the minimum complexity which must be supported by a VRML interpreter. Interpreter implementations may choose to support greater limits but may not reduce the limits described in Table 7-1. When the metafile being interpreted contains nodes which exceed the latitude implemented by the interpreter, the interpreter will attempt to skip that node and continue at the next node. Where latitude is specified in this table for a particular node, full support is required for other aspects of that node.

Contact rikk@best.com, cmarrin@sgi.com, or gavin@acm.org with questions or comments.

This URL: http://vrml.sgi.com/moving-worlds/spec/part1/conformance.html