<!-- ====================================================================== -->
<!-- GRAPHML DTD (flat version) =========================================== -->
<!-- file: graphml.dtd 

            SYSTEM "http://graphml.graphdrawing.org/dtds/graphml.dtd"
 
            xmlns="http://graphml.graphdrawing.org/xmlns/graphml"
            (consider these urls as examples)

    ====================================================================== -->


<!--============================================================-->
<!--elements of GRAPHML-->
<!--============================================================-->


<!ELEMENT graphml  ((desc)?,(key)*,((data)|(graph))*)>


<!ELEMENT locator EMPTY>
<!ATTLIST locator 
          xmlns:xlink   CDATA    #FIXED    "http://www.w3.org/TR/2000/PR-xlink-20001220/"
          xlink:href    CDATA    #REQUIRED
          xlink:type    (simple) #FIXED    "simple"
>

<!ELEMENT desc (#PCDATA)>


<!ELEMENT graph    ((desc)?,((((data)|(node)|(edge)|(hyperedge))*)|(locator)))>
<!ATTLIST graph    
          id          ID                    #IMPLIED
          edgedefault (directed|undirected) #REQUIRED
>   

<!ELEMENT node   (desc?,(((data|port)*,graph?)|locator))>
<!ATTLIST node   
          id        ID      #REQUIRED
>
  
<!ELEMENT port ((desc)?,((data)|(port))*)>
<!ATTLIST port
          name    NMTOKEN  #REQUIRED
>


<!ELEMENT edge ((desc)?,(data)*,(graph)?)>
<!ATTLIST edge 
          id         ID           #IMPLIED
          source     IDREF        #REQUIRED
          sourceport NMTOKEN      #IMPLIED
          target     IDREF        #REQUIRED
          targetport NMTOKEN      #IMPLIED
          directed   (true|false) #IMPLIED
>


<!ELEMENT hyperedge  ((desc)?,((data)|(endpoint))*,(graph)?)>
<!ATTLIST hyperedge 
          id     ID      #IMPLIED
>

<!ELEMENT endpoint ((desc)?)>
<!ATTLIST endpoint 
          id    ID             #IMPLIED
          node  IDREF          #REQUIRED
          port  NMTOKEN        #IMPLIED
          type  (in|out|undir) "undir"
>


<!ELEMENT key (#PCDATA)>
<!ATTLIST key 
          id  ID                                            #REQUIRED
          for (graph|node|edge|hyperedge|port|endpoint|all) "all"
>   

<!ELEMENT data  (#PCDATA)>
<!ATTLIST data 
          key      IDREF        #REQUIRED
          id       ID           #IMPLIED
>

<!--==============================================================
     end of graphml.dtd
=================================================================-->