/// <summary>
 /// Ctor
 /// </summary>
 /// <param name="ns">fully qualified XMP namespace URI</param>
 public XmpBasicPropertyAttribute(XmpBasicType valueType, XmpQuantity quantity)
 {
     this.ValueType = valueType;
     this.Quantity  = quantity;
 }
 /// <summary>
 /// Ctor
 /// </summary>
 /// <param name="ns">fully qualified XMP namespace URI</param>
 public XmpBasicPropertyAttribute(XmpBasicType valueType)
 {
     this.ValueType = valueType;
 }