platform/core-impl/src/com/intellij/codeInsight/documentation/DocumentationManagerProtocol.java

package com.intellij.codeInsight.documentation;

import org.jetbrains.annotations.NonNls;

public interface DocumentationManagerProtocol {
  @NonNls String PSI_ELEMENT_PROTOCOL = "psi_element://";
  @NonNls String DOC_ELEMENT_PROTOCOL = "doc_element://";
}