http://geoapi.sourceforge.net/snapshot/javadoc/index.html
package :
org.opengis.style

To tests on the go-renderer, I committed a basic implementation in the unsupported GO module.
package :
org.geotools.styling2

class StyleFactoryImpl extends AbstractStyleFactory implements StyleFactory2,
                                                           /** org.opengis.style.StyleFactory*/ {
    ...
    /**
     * Create an LineSymbolizer using stroke to draw the indicated geometry.
     * @param stoke Description of how to draw the line segments
     * @param geometryExpression Expression evaluating to a Geometry.
     *        (For SLD 1.1 documents this should be a PropertyName expression)
     * @since 2.6.0
     */
    LineSymbolizer lineSymbolizer( Stroke stroke, Expression geometryExpression );

    Rule rule();
    /**
     * ...
     * @param symbolizers List of symbolizers to use; these symbolizers will be copied into
     *                    an internal list so we can issue events.
     * ...
     */
    Rule rule( Description description, Filter filter, List<Symbolizer> symbolizers, LegendGraphic, double minScale, double maxScale, boolean isElse );

    ...

}

public interface LineSymbolizer extends Symbolizer {
    Stroke getStroke();

    /** @deprecated Not thread safe - please use DuplicatingStyleVisitor */
    void setStroke(Stroke stroke);

    String getGeometryPropertyName();

    /** @deprecated Not thread safe - please use DuplicatingStyleVisitor */
    void setGeometryPropertyName(String geometryPropertyName);
}

public interface LineSymbolizer extends Symbolizer implements org.opengis.style.LineSymbolizer {

    @Override Type narrow org.opengis.style.Stoke to Stroke
    Stroke getStroke();

    /** @deprecated Not thread safe - please use DuplicatingStyleVisitor */
    void setStroke(Stroke stroke);

    String getGeometryPropertyName();

    /** @deprecated Not thread safe - please use DuplicatingStyleVisitor */
    void setGeometryPropertyName(String geometryPropertyName);
}

public interface FeatureTypeStyle {
    ...
    Rule[] getRules();
    void setRules(Rule[] rules);
    void addRule(Rule rule);
}
public interface Rule {
    ...
}

public interface FeatureTypeStyle extends org.opengis.FeatureTypeStyle {
    ...
    /** Same as: rules().toObjectArray( new Rule[0] ) */
    @Deprecated
    Rule[] getRules();

    /** Same as:
     * rules().clear()
     * rules().addAll( Arrays.asList( rules ) );
    @Deprecated
    void setRules(Rule[] rules);

    /** same as rules().add( Rule ) */
    @Deprecated
    void addRule(Rule rule);

    /** Offer direct access to the rules list; contents are assumed to be org.geotools.styling.Rule */
    @override
    List<org.opengis.style.Rule> rules();
}
public interface Rule extends org.opengis.Rule {
    ...
}

public interface FeatureTypeStyle extends org.opengis.FeatureTypeStyle {
   addStyleListener( StyleListener listener );
   removeStyleListener( StyleListener listener );
}
public interface Rule extends org.opengis.Rule {
   addStyleListener( StyleListener listener );
   removeStyleListener( StyleListener listener );
}
/** Utility class for Style implementors - issues events when asked */
public StyleList extends ArrayList {
   addStyleListener( StyleListener listener );
   removeStyleListener( StyleListener listener );
}

NEW METHODS
    /**
     * Returns a collection of Object identifying features object.
     *
     * <p>
     * ISO 19117 extends FeatureTypeStyle be providing this method.
     * This method enable the possibility to use a feature type style
     * on a given list of features only, which is not possible in OGC SE.
     * </p>
     *
     * @return Collection<String>
     */
    @UML(identifier="definedForInst", obligation=OPTIONAL, specification=ISO_19117)
    Id getFeatureInstanceID();

    /**
     * Returns a semanticType that identifies the more general "type" of geometry
     * that this style is meant to act upon.
     * In the current OGC SE specifications, this is an experimental element and
     * can take only one of the following values:
     * <p>
     * <ul>
     *   <li>{@code generic:point}</li>
     *   <li>{@code generic:line}</li>
     *   <li>{@code generic:polygon}</li>
     *   <li>{@code generic:text}</li>
     *   <li>{@code generic:raster}</li>
     *   <li>{@code generic:any}</li>
     * </ul>
     * <p>
     *
     */
    Set<SemanticType> getSemanticTypeIdentifiers();

NEW METHOD
    /**
     * Returns a string of containing the measure unit name.
     * This parameter is herited from GML.
     * Renderers shall use the unit to correctly render symbols.
     *
     * recommended uom definitions are :
     * <p>
     * <ul>
     *     <li>{@code metre}</li>
     *     <li>{@code foot}</li>
     *     <li>{@code pixel}</li>
     * </ul>
     * <p>
     *
     * @return String name for the measure unit to use,
     * can be null. If the unit is null than we shall use a the pixel unit
     */
    @XmlElement("uom")
    Unit getUnitOfMeasure();

public interface ColorMap {
    public static final int TYPE_RAMP = 1;
    public static final int TYPE_INTERVALS = 2;
    public static final int TYPE_VALUES = 3;

    public void addColorMapEntry(ColorMapEntry entry);

    public ColorMapEntry[] getColorMapEntries();

    public ColorMapEntry getColorMapEntry(int i);

    public int getType();

    public void setType(int type);

    void accept(StyleVisitor visitor);

    public void setExtendedColors(boolean extended);

    public boolean getExtendedColors();
}

public interface ColorMap {
    /** This is a live view of the ColorMap in function form*/
    Function getFunction();
}