class TXMLFile: public TFile, public TXMLSetup

 default TXMLFile constructor

 Open or creates local XML file with name filename.
 It is recommended to specify filename as "<file>.xml". The suffix ".xml"
 will be used by object browsers to automatically identify the file as
 a XML file. If the constructor fails in any way IsZombie() will
 return true. Use IsOpen() to check if the file is (still) open.

 If option = NEW or CREATE   create a new file and open it for writing,
                             if the file already exists the file is
                             not opened.
           = RECREATE        create a new file, if the file already
                             exists it will be overwritten.
           = 2xoo            create a new file with specified xml settings
                             for more details see TXMLSetup class
           = UPDATE          open an existing file for writing.
                             if no file exists, it is created.
           = READ            open an existing file for reading.

 For more details see comments for TFile::TFile() constructor

 For a moment TXMLFile does not support TTree objects and subdirectories

 initialize xml file and correspondent structures
 identical to TFile::Init() function

 Close a XML file
 For more comments see TFile::Close() function

 destructor of TXMLFile object

 make private to exclude copy operator

 return kTRUE if file is opened and can be accessed

 Reopen a file with a different access mode, like from READ to
 See TFile::Open() for details

 create XML key, which will store object in xml structures

 create XML key, which will store object in xml structures

 function produces pair of xml and dtd file names

 Saves xml structures to file
 xml elements are kept in list of TKeyXML objects
 When saving, all this elements are linked to root xml node
 In the end StreamerInfo structures are added
 After xml document is saved, all nodes will be unlinked from root node
 and kept in memory.
 Only Close() or destructor relase memory, used by xml structures

 Connect/disconnect all file nodes to single tree before/after saving

 read document from file
 Now full content of docuument reads into the memory
 Then document decomposed to separate keys and streamer info structures
 All inrelevant data will be cleaned

 Read list of keys for directory

 convert all TStreamerInfo, used in file, to xml format

 Read streamerinfo structures from xml format and provide them in the list
 It is user responsibility to destroy this list

 store data of single TStreamerElement in streamer node

 read and reconstruct single TStreamerElement from xml node

 Change layout of objects in xml file
 Can be changed only for newly created file.

 Currently there are two supported layouts:

 TXMLSetup::kSpecialized = 2
    This is default layout of the file, when xml nodes names class names and data member
    names are used. For instance:
          <TAttLine version="1">
            <fLineColor v="1"/>
            <fLineStyle v="1"/>
            <fLineWidth v="1"/>
          </TAttLine>

 TXMLSetup::kGeneralized = 3
    For this layout all nodes name does not depend from class definitions.
    The same class looks like
          <Class name="TAttLine" version="1">
            <Member name="fLineColor" v="1"/>
            <Member name="fLineStyle" v="1"/>
            <Member name="fLineWidth" v="1"/>
          </Member>

 If true, all correspondent to file TStreamerInfo objects will be stored in file
 this allows to apply schema avolution later for this file
 may be usefull, when file used outside ROOT and TStreamerInfo objects does not required
 Can be changed only for newly created file.

 Specify usage of DTD for this file.
 Currently this option not available (always false).
 Can be changed only for newly created file.

 Specifiy usage of namespaces in xml file
 In current implementation every instrumented class in file gets its unique namespace,
 which is equal to name of class and refer to root documentation page like
 <TAttPad xmlns:TAttPad="http://root.cern.ch/root/htmldoc/TAttPad.html" version="3">
 And xml node for class member gets its name as combination of class name and member name
            <TAttPad:fLeftMargin v="0.100000"/>
            <TAttPad:fRightMargin v="0.100000"/>
            <TAttPad:fBottomMargin v="0.100000"/>
            and so on
 Usage of namespace increase size of xml file, but makes file more readable
 and allows to produce DTD in the case, when in several classes data member has same name
 Can be changed only for newly created file.

 Add comment line on the top of the xml document
 This line can only be seen in xml editor and cannot be accessed later
 with TXMLFile methods

 Adds style sheet definition on the top of xml document
 Creates <?xml-stylesheet alternate="yes" title="compact" href="small-base.css" type="text/css"?>
 Attributes href and type must be supplied,
  other attributes: title, alternate, media, charset are optional
 if alternate==0, attribyte alternate="no" will be created,
 if alternate>0, attribute alternate="yes"
 if alternate<0, attribute will not be created
 This style sheet definition cannot be later access with TXMLFile methods.

 Add just one line on the top of xml document
 For instance, line can contain special xml processing instructions
 Line should has correct xml syntax that later it can be decoded by xml parser
 To be parsed later by TXMLFile again, this line should contain either
 xml comments or xml processing instruction

 Create key for directory entry in the key

 Serach for key which correspond to direcory dir

Find a directory in motherdir with a seek equal to keyid

 Read keys for directory
 Make sence only once, while next time no new subnodes will be created

 Update key attributes

Write the directory header

 Interface to basic system I/O routines