COLLADA provides flexibility by allowing applications to define extensions to existing COLLADA elements. These extensions take the form of alternative <technique> elements, additive <extra> elements, and scalable <input> elements.
<extra> elements and of <technique> elements with the argument profile indicating the platform (product name or similar) to which the extension applies.
Extension by Alternative
COLLADA enables multi-representation of many elements. In such cases, the element is defined using one <technique_common> and zero or more <technique> elements. The common technique is a representation of the element that is strongly typed in the schema and is required.
Other techniques are defined by the vendor supplying the alternative representation. Each <technique> has a profile attribute indicating the platform (product name or similar) to which the extension applies.
Each alternative representation of an extensible element should contain values that describe the element for that profile. The representations may have coherency between profiles although that is not required. In other words, if <technique_common> describes an ambient light it is okay if a <technique> for that light describes something else like an area light for that profile.
Using <technique> to choose profiles
A COLLADA processor will choose either one, and only one, of the available alternatives. It will choose the <technique_common> or one of the <technique> elements. Where alternative choices are possible within the schema, the <technique> element models the alternative extensions. For example:
<light> <technique_common> <ambient> <color/> </ambient> </technique_common> <technique profile="alternative_1"/> <technique profile="alternative_2"/> </list>