7.1 Introduction and topics

7.1.1 Introduction

This clause defines the minimum required support for language bindings conforming to this part of ISO/IEC 19775.

7.1.2 Topics

Table 7.1 lists the topics for this clause.

7.1.3 Objectives

This clause addresses conformance of X3D browsers that provide a scene authoring interface (SAI).

The primary objectives of the specifications in this clause are:

1. to promote interoperability by eliminating arbitrary subsets of ISO/IEC 19775;
2. to promote extensibility within a well-defined environment;
3. to promote uniformity in the development of conformance tests;
4. to promote consistent results across X3D browsers;
5. to facilitate automated test generation.

7.1.4 Scope

Conformance is defined for language bindings to this specification and therefore X3D Browsers and applications that use the facilities provided by the Scene Authoring Interface language-specific bindings as specified in ISO/IEC 19777.

Due to the abstract nature of this specification, it is not possible to specify the conformance tests of individual language bindings of the specification. Separate Conformance sections shall be provided within each language binding that provide the necessary information to implement language-specific binding conformance tests.

A concept of base profile conformance is defined to ensure interoperability of X3D applications and X3D browsers. Base profile conformance is based on a set of limits and minimal requirements. Base profile conformance is intended to provide a functional level of reasonable utility for X3D language bindings while limiting the complexity and resource requirements of X3D browsers. Base profile conformance may not be adequate for all uses of the SAI.

7.2 Conformance

7.2.1 Conformance to this part of ISO/IEC 19775

A X3D browser is only conformant to this part of ISO/IEC 19775 if it also conformant to the current profile as specified in ISO/IEC 19775-1. In addition, the following conditions shall be met:

1. Requests of the Browser services shall conform exactly to the behaviour as specified in this part of ISO/IEC 19775.
2. Where a browser is required to read and parse X3D content, it shall be able to handle any X3D file that conforms to the profile being supported as defined in ISO/IEC 19775-1 or separate specification for such profiles.
3. Only nodes in the top level world (the file defined by the getWorldURL service) that are named with the DEF construct shall be visible to the getNode browser service request.
4. There shall be no difference in treatment of events that result from an external service request compared to events generated within the X3D browser environment. That is, externally generated event cascades shall have no favoured treatment.

7.2.2 Language bindings

A language binding to this part of ISO/IEC 19775 is conforming if:

1. It implements the services defined in this specification including return values, error conditions and asynchronous events.
2. The services implemented conform to the required functionality for the subject profile.
3. It provides sections outlining conformance and minimum requirements of implementations of that binding.

7.3 Minimum Requirements

7.3.1 Requirements for implementations

All profiles supporting the authoring component shall support the Level 1 functionality as defined in this section. There are two levels of conformance, that of the language binding and the browser implementation.

A language binding shall at a minimum implement the services required for the profile to be supported. It may also define its own optional set of minimum requirements that are no less than the requirements of this section. A browser implementation shall, in addition to the base support for the subject profile, also support the minimum capabilities defined for the subject profile. In general, the browser requirements are specified as general requirements that deal with specific language issues.

Where a browser implements two or more language bindings with different levels of minimum requirements, the browser shall support the minimum requirements for each language separately. Therefore, if one language has higher requirements, the lower requirements of the other shall not be used.

7.3.2 Supporting internal and external interactions

Although external interactions use a superset of the services defined for internal interactions, language bindings to the abstract specification are not required to implement both. They may choose one or the other or both. (It is strongly recommended that a binding support both.)

A conformant browser implementation is not required to provide both internal and external implementations of a given language binding. It shall be possible for a browser to support internal interactions only with language A and external interactions only with language B. In addition, the browser may choose to support only internal interactions or only external interactions. There is no requirement to support both internal and external interactions.

7.3.3 Level 1

Table 7.2 through Table 7.6 define the minimum requirements for a base profile. The first column specifies the item for which conformance is being defined. These refer to the services as defined by this specification. The second column specifies the requirements for a language binding specification of that item. The third column specifies the requirements of a browser implementation of that service. SAI implementations shall throw an SAIError (such as SAI_NOT_SUPPORTED) if a capability is not supported.

For all these requirements, it shall be assumed that the language binding shall provide complete implementation of all the parameters required for the individual services. Language bindings of data types may be implemented as primitive types in the target language rather than as separate data types. Table 7.2 through Table 7.6 indicate where this is permitted.

A browser conformant to this level shall support bindings to the X3DNode and X3DMetadataObject abstract representations along with all field types.

7.3.4 Level 2

A browser conformant to Level 2 shall support everything in Level 1 and shall support all abstract node types derived from X3DNode for the components implemented in the browser. The browser shall also support all additional objects that may be introduced by the implementation.

7.3.5 Level 3

A browser conformant to Level 3 shall support all of the requirements of Level 2 and also support binding specific interfaces for each concrete node representation.