http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
public final class javax.xml.XMLConstants
  minor version: 0
  major version: 59
  flags: flags: (0x0031) ACC_PUBLIC, ACC_FINAL, ACC_SUPER
  this_class: javax.xml.XMLConstants
  super_class: java.lang.Object
{
  public static final java.lang.String NULL_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: ""

  public static final java.lang.String DEFAULT_NS_PREFIX;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: ""

  public static final java.lang.String XML_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/XML/1998/namespace"

  public static final java.lang.String XML_NS_PREFIX;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "xml"

  public static final java.lang.String XMLNS_ATTRIBUTE_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/2000/xmlns/"

  public static final java.lang.String XMLNS_ATTRIBUTE;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "xmlns"

  public static final java.lang.String W3C_XML_SCHEMA_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/2001/XMLSchema"

  public static final java.lang.String W3C_XML_SCHEMA_INSTANCE_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/2001/XMLSchema-instance"

  public static final java.lang.String W3C_XPATH_DATATYPE_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/2003/11/xpath-datatypes"

  public static final java.lang.String XML_DTD_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/TR/REC-xml"

  public static final java.lang.String RELAXNG_NS_URI;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://relaxng.org/ns/structure/1.0"

  public static final java.lang.String FEATURE_SECURE_PROCESSING;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://javax.xml.XMLConstants/feature/secure-processing"

  private void <init>();
    descriptor: ()V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // javax.xml.XMLConstants this
         0: .line 41
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 42
            return
        end local 0 // javax.xml.XMLConstants this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    2     0  this  Ljavax/xml/XMLConstants;
}
SourceFile: "XMLConstants.java"