EDIT

      <extension

            point="org.eclipse.core.expressions.definitions">

         <definition

               id="isSequence">

            <with

                  variable="selection">

               <test

                     property="eu.etaxonomy.taxeditor.molecular.SpecimenPropertyTester.isSequence">

               </test>

            </with>

         </definition>

         <definition

               id="isSingleRead">

            <with

                  variable="selection">

               <test

                     property="eu.etaxonomy.taxeditor.molecular.SpecimenPropertyTester.isSingleRead">

               </test>

            </with>

         </definition>

      </extension>

      <extension

            point="org.eclipse.core.expressions.propertyTesters">

         <propertyTester

               class="eu.etaxonomy.taxeditor.molecular.handler.SpecimenPropertyTester"

               id="eu.etaxonomy.taxeditor.molecular.SpecimenPropertyTester"

               namespace="eu.etaxonomy.taxeditor.molecular.SpecimenPropertyTester"

               properties="isSequence,isSingleRead"

               type="org.eclipse.jface.viewers.IStructuredSelection">

         </propertyTester>

      </extension>

package eu.etaxonomy.taxeditor.molecular.handler;

import org.eclipse.core.expressions.PropertyTester;

import org.eclipse.jface.viewers.IStructuredSelection;

import org.eclipse.jface.viewers.TreeNode;

import eu.etaxonomy.cdm.model.molecular.Sequence;

import eu.etaxonomy.cdm.model.molecular.SingleRead;

import eu.etaxonomy.taxeditor.editor.EditorUtil;

/**

 * Tests types of specimens to add items to the context menu.

 *

 * @author pplitzner

 * @author BenStoever

 */

public class SpecimenPropertyTester extends PropertyTester {

    private static final String SEQUENCE = "isSequence";

    private static final String SINGLE_READ = "isSingleRead";

    public SpecimenPropertyTester() {}

    /* (non-Javadoc)

     * @see org.eclipse.core.expressions.IPropertyTester#test(java.lang.Object, java.lang.String, java.lang.Object[], java.lang.Object)

     */

    /** {@inheritDoc} */

    @Override

    public boolean test(Object receiver, String property, Object[] args, Object expectedValue) {

        if (receiver instanceof IStructuredSelection) {

            IStructuredSelection selection = (IStructuredSelection) receiver;

            TreeNode treeNodeOfSelection = EditorUtil.getTreeNodeOfSelection(selection);

            if (treeNodeOfSelection!=null) {

                if (SEQUENCE.equals(property)) {

                    return isSequence(treeNodeOfSelection.getValue());

                }

                else if (SINGLE_READ.equals(property)) {

                	return isSingleReadAlignment(treeNodeOfSelection.getValue());

                }

            }

        }

        return false;

    }

	private boolean isSequence(Object object) {

    	return (object instanceof Sequence);

	}

	private boolean isSingleReadAlignment(Object object) {

    	return (object instanceof SingleRead);

    }

}