The SubsAttribute command replaces the value of attribute attrName with attrValue in the XML element xmlTree.

The attribute can be specified in two ways.

- As a pair consisting of the name attrName of the attribute and its new value attrValue.

- As an equation attr. Specifying the attribute substitution as an equation is equivalent to using SubsAttribute(xmlTree, lhs(attr), rhs(attr)).

A new XML element with the attribute attrName that has the new specified value is returned. The original value of the attribute attrName (which may or may not be the same as the new value attrValue) is discarded.

The SubsAttributeName command replaces the name of an attribute in the XML element xmlTree.

The attribute can be specified in two ways.

- As a pair consisting of the name attrName of the attribute and its new name newName.

- As an equation attr2 representing the substitution of the old name for the new. Specifying the attribute substitution as an equation attr2 is equivalent to using SubsAttributeName(xmlTree, lhs(attr2), rhs(attr2)).

A new XML element is returned where the original attribute attrName is replaced by one named newName, but newName has the value of the original attribute.

Both of these functions return an error if the XML element represented by xmlTree has no attribute named attrName.

<a colour = 'red'>some text</a>

<a colour = 'blue'>some text</a>

<a colour = 'blue'>some text</a>

<a color = 'red'>some text</a>

<a color = 'red'>some text</a>

Error, (in unknown) element does not have an attribute called "color"