The attribute value is a is a functional notation value (like a ), which must take a string as a parameter a string with Name Token production (i.e., the same syntax as allowed in a query string parameter name). This string parameter must be evaluated to match, in a case-sensitive manner, the the 'name' portion of the name-value parameter pair passed into the document and exposed through the Parameters interface. If this parameter value does match a parameter name, it must return a string which shall be the corresponding 'value' portion of the matching name-value parameter pair, which shall serve as the attribute value of the attribute. If this parameter value does not match a parameter name, or if this parameter value is not a Name Token, the he attribute value function must return an empty string (""), and the value of the attribute shall be the attribute's fallback value, or if there is no fallback value provided, the value of the attribute shall be the attribute's lacuna value.

　　attribute value parameters which do not match any 'name' portions of a parameter must not raise any errors, and it must not constitute an unresolved reference. Error-handling must not be applied because of a missing parameter.

　　attribute values must be evaluated immediately upon the loading of the file, or whenever the parameter information becomes available. If the parameter information changes, all attribute values must be updated to reflect the new values, and any rendering changes must be applied. If the parameter information changes, and a the new information does not contain a name that was previously matched by the attribute values parameter, then the affected attribute value must be processed as described above.

　　For which conform to this specification, the attribute value must be available as a value on any SVG attribute. For attributes which take a list as a value, each attribute value used shall constitute a separate value on that list. For attributes which do not take a list as a value, the following syntax must be applied to attribute values which use a attribute value:

　　where the optional string is a fallback value that would otherwise be a permitted value for that attribute.

　　The attribute may be placed on any textual element, such as the , , or elements, and takes as a value the attribute value. For any matching parameter name, the corresponding parameter value shall be placed into the DOM as the child of the textual element, replacing any existing child content.

　　The property shall acts as a mechanism to pass parameters to referenced resources, by means of a comma-separated list of name-value string pairs. Each name-value pair shall consist of a string representing the name, followed by a colon (":"), followed by a string representing the value. If either the name or value string contains spaces or punctuation marks, it must be enclosed in double or single quotes [note: define this better]. If this property value does not conform to this syntax, all name-value pairs after the first error must be discarded.

　　This property may be expressed as an attribute or as a CSS property in a class, attribute, or other CSS mechanism. This property is inheritable and animatable.

　　The element shall acts as a mechanism to pass parameters to referenced resources, in a manner similar to the HTML element of the HTML element [HTML4].

　　Every element shall have a attribute and an attribute to represent both portions of a name-value pair, which shall be available to the referenced element. If a element does not have a value for either or both of the or attributes, the element shall not be passed to the referenced content.

　　The name-value parameter pair shall be passed to to the content referenced in the element's parent element. If the parent element does not reference any content, all child elements shall be ignored. Note that not all referenced content may have the ability to accept parameters, for instance if it does not have a DOM, as with a raster image. How non-SVG referenced content deals with parameters is outside the scope of this document.

　　3.7.1 Relevant SVG Referencing Elements

　　In SVG, there are several elements which reference content. This content may normally be either a local or external resources, and it may be SVG content or other types of content (e.g. a raster image or HTML document).

　　The following SVG elements may reference SVG , and must pass on parameters from child elements: , , , and . Other elements which reference content, such as , , and , may pass on parameters, but the result of such behavior is not defined in this specification.

　　Parameters and the Elements

　　In the case of the element, the element may have child elements, and these name-value parameter pairs must be passed on to the referenced content. The element's shadow tree must implement the Parameters and WindowParameters interfaces. These instances of the interfaces must be scoped to the shadow tree, and must not apply to content outside the shadow tree, including even the referenced document fragment. In the case of local references, if the document has parameters, these parameters are imported into the element's shadow tree, and any parameters specific to the element will override the parameters from the document's Parameters interface.