# Implementation dependent features

## Chunking

Supported chunking methods:

- select-topic
- select-document
- select-branch
- by-topic
- by-document
- to-content
- to-navigation.

When no chunk attribute values are given, no chunking is performed.

Note: In effect, for HTML based transformation types this is equivalent to select-document and by-document defaults.

Error recovery:

- When two tokens from the same category are used, no error or warning is thrown.
- When an unrecognized chunking method is used, no error or warning is thrown.

## Filtering

Error recovery:

- When there are multiple revprop elements with the same val attribute, no error of warning is thrown
- When multiple prop elements define a duplicate attribute and value combination, attribute default, or fall-back behaviour, DOTJ007E error is thrown.

## Debug attributes

The debug attributes are populated as follows:

xtrf
  absolute system path of the source document
xtrc
  element counter that uses the format

      element-name ":" integer-counter

## Image scaling

If both height and width attributes are given, image is scaled nonuniformly.

If scale attribute is not an unsigned integer, no error or warning is thrown during preprocessing.