Syntax

using attribute-reference (as alias-name)?
   action

You can use using to create an alias for an attribute in the current parsing state. Attributes available in the current parsing state include the attributes of the current element and the attributes of all open elements.

Suppose that you are processing an element called "section" that has a parent called "chapter" and the "chapter" element has an attribute "number". You can access the "number" attribute of the "chapter" element as follows:

  element "section"
     output attribute "number" of parent

You can use using to simplify the reference to this attribute by enabeling you to refer to it by its attribute name alone (and thus to use the %v format item):

  element "section"
     using attribute "number" of parent
        output "%v(number)"

This is valuable because when an attribute is output using %v, translate rules are applied to it. If it is output using the attribute keyword or is read from the attributes shelf, translate rules are not applied.

Suppose that the "section" element also has an attribute "number". In this case we need to be able to distinguish between the two attribute names. To do this we can add an as clause to using to give the chapter level "number" attribute another name in the local scope:

  element "section"
     using attribute "number" of parent as "chapter-number"
        output "%v(chapter-number).%v(number)"  

To further clairify this code, we can use using to give the local "number" attribute a distinct name also:

  element "section"
     using attribute "number" as "section-number"
     using attribute "number" of parent as "chapter-number"
        output "%v(chapter-number).%v(section-number)"  

The scope of the using prefix is the lexical scope to which it applies (either the following action, or a scope defined by a block).

When used with an attribute, the using prefix must include either an element specifier (introduced by of) or an alias (introduced by as), or both.

You can refer to the attribute you are interested in using either the attribute keyword (as in the examples above) or by refering to items on the attributes shelf, as shown below:

  element "section"
     using attributes {"number"} as "section-number"
     using attributes of parent {"number"} as "chapter-number" 
        output "%v(chapter-number).%v(section-number)"  

You can also use using with the data-attribute keyword and the data-attributes shelf in the same way.

Finally, you can use using to select an item from a list valued attribute:

  element "foo"
     using attribute "bar" [3] as "bar-3"
        output "%v(bar-3)"  

Related Syntax    #markup-parser    attribute    attributes    repeat over, #item, #last, #first

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