var
  i, j: Integer;
const
  ncnt = 60;
var
  aXMLStreamWriter: TGRAPHMLStreamWriter;
  h1, h2: string;
begin
  aXMLStreamWriter := TGRAPHMLStreamWriter.Create;
  try

    aXMLStreamWriter.AddHeader;

    aXMLStreamWriter.StartTag('graph');
    aXMLStreamWriter.SetAttribute('id', 'G');
    aXMLStreamWriter.SetAttribute('edgedefault', 'undirected');

    for i := 0 to ncnt do
    begin
      aXMLStreamWriter.StartTag('node');
      aXMLStreamWriter.SetAttribute('id', 'n' + IntToStr(i));
      aXMLStreamWriter.StopTag;
    end;

    for i := 0 to ncnt do
    begin
      h1 := 'n' + IntToStr(i);
      h2 := 'n' + IntToStr( ( i +1 ) mod ncnt );
      aXMLStreamWriter.StartTag('edge');
      aXMLStreamWriter.SetAttribute('source', h1);
      aXMLStreamWriter.SetAttribute('target', h2);
      aXMLStreamWriter.StopTag;
    end;

    aXMLStreamWriter.StopTag;

    aXMLStreamWriter.AddFooter;

    aXMLStreamWriter.SavetoFile('e:\test.graphML');

  finally
    XMLMemo.Lines.Add(aXMLStreamWriter.ToString);

    XMLMemo.Lines.SavetoFile('e:\test2.graphML');
  end;

type
  TXMLStreamWriter = class

  private

    /// <summary>
    /// end the current string/TAG with a new line
    /// </summary>
    FNewLineWritten: Boolean;

    FIsStartTagClosed: Boolean;

    FStream: TStringStream;

    FTagStack: TStringStack;
    /// <summary>
    /// original comment : not entirely correct implementation as some names
    /// are correct <br />but it still returns False, but that occurs only
    /// with names using <br />characters outside the american alphabet
    /// </summary>
    function IsValidTagName(const ATagName: WideString): Boolean;

    /// <summary>
    /// a too simple check for invalid characters, more or less correct for
    /// ANSI names.
    /// </summary>
    /// <remarks>
    /// [#0..#$40,#$5B..#$60,#$7B..#$FF]; <br />InvalidOtherChar =
    /// [#0..#$2C,#$5B..#$60,#$7B..#$B6,#$B8..#$FF]; <br />
    /// ValidNameOtherChar:WideString =
    /// ['a'..'z','A'..'Z','_',':','0'..'9','.','-'];
    /// </remarks>
    function IsValidAttributeName(const AAttributeName: WideString): Boolean;

    procedure Indent;

    function IsTagStarted: Boolean;

    function LastTag: String;

    function MakeValidAttributeValue(const AValue: String): String;

    procedure AssertLastTagClosed;

  public

    constructor Create;

    destructor Destroy; override;



    procedure AddRaw(const Data: String);

    procedure AddNewLine;

    procedure SetAttribute(const Attribute, Value: String);

    function ToString: String;

    procedure StartTag(const Tag: String);

    procedure StopTag;

    procedure SavetoFile(Filename : string);



  end;


type

  TGRAPHMLStreamWriter = class(TXMLStreamWriter)


  procedure AddHeader;

  procedure AddFooter;
  end;





implementation
{ TXMLStreamWriter }


function TXMLStreamWriter.IsValidTagName(const ATagName: WideString): Boolean;
begin
  Result := IsValidAttributeName(ATagName);
end;



procedure TXMLStreamWriter.SavetoFile(Filename: string);
begin
    FStream.SaveToFile(Filename);
end;


procedure TXMLStreamWriter.AddRaw(const Data: String);
var
  StrLen: integer;
begin
  // Stream.WriteBuffer(Pointer(Str)^, StrLen * SizeOf(Char)); //All Delphi versions compatible
  StrLen := length(Data);
  self.FStream.WriteBuffer(Pointer(Data)^, StrLen * SizeOf(Char))
end;

constructor TXMLStreamWriter.Create;
begin
  FTagStack := TStringStack.Create;

  FStream := TStringStream.Create('', TEncoding.UTF8);

  FIsStartTagClosed := True;
end;

destructor TXMLStreamWriter.Destroy;
begin
  FTagStack.Free;

  FStream.Free;

  inherited;
end;

function TXMLStreamWriter.ToString: String;
begin
  Result := self.FStream.DataString;
end;


{ TGRAPHMLStreamWriter }

procedure TGRAPHMLStreamWriter.AddFooter;
begin
    self.AddRaw('</graphml>');
end;

procedure TGRAPHMLStreamWriter.AddHeader;
begin
  self.AddRaw('<?xml version="1.0" encoding="UTF-8"?> ');
  self.AddRaw('<graphml xmlns="http://graphml.graphdrawing.org/xmlns" ');
  self.AddRaw('xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" ');
  self.AddRaw('xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns ');
  self.AddRaw('http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd"> ');
  AddNewLine;
end;