* </p>
 *
 * <p>
 * Example Usage:
 * </p>
 *
 * <pre>
 * XmlTransformer transformer = new XmlTransformer();
 * transformer.setNamespaceAware(true);
 * transformer.setCacheDuration(30);
 * transformer.addFieldRule("title", "/book/title/text()");

```

**Rule**: Pattern-based response routing (`RegexRule`, `SitemapsRule`)
**ResponseProcessor**: `DefaultResponseProcessor`, `SitemapsResponseProcessor`, `NullResponseProcessor`
**Transformer**: `HtmlTransformer`, `XmlTransformer`, `FileTransformer`, etc.
**Extractor**: Weight-based selection (tries in descending weight order)

### Key Extractors