//=============================================================================
//
// General Description of Data Access Module
//
// Created:	       	10/01/99
// Author:			Hyun Kim
//
//=============================================================================


(1) dataModule.java

	- General class for accessing data through different protocols
	- METHODs: 
	
	  public void open( String protocol, String location, String id, String pwd ) throws Exception;
		. protocol: specify a certain protocol to open its session
			(such as "file", "jdbc", "web", "ldap"(currently suspended))
		. location: path of filename or URL
		. id, pwd: ID and its password for access to database or LDAP	
		
	  public void update();
	    . save the changes
	    
	  public void update( String location );
	    . save the changes into the given location
	    
	  public void close();
	    . close the session without saving

      public Enumeration getTypes();
        . get the list of all types, such as 'user'
        
	  public String getValue( String type, String name, String key );
		. get the value of the specified key of the given type's and name's object

   	  public Enumeration getObjects( String types );
		. get the list of all given type's objects 

	  public void addObject( String type, String name ) throws Exception;
		. add the new object with the given type and name
		. if the given type's and name's object alreadt exists, all keys of the object are 
		  removed and added as a new object

	  public void removeObject( String type, String name ) throws Exception;
		. remove all keys of the given name's user
		. do nothing if the given type's and name's object does not exist

	  public Enumeration getObjectKeys( String type, String name );
		. get the list of all keys of the given type's and name's object

	  public void setValue( String type, String name, String key, String value ) throws Exception;
		. modify the value of the given key of the given type's and name's object
		. do nothing if the given type's and name's object does not exist
		. add the key and its value if the given key does not exists

	  public void removeKey( String type, String name, String key ) throws Exception;
		. remove the given key and its value
		. do nothing if the given type's and name's user or the given key does not exist

[EXAMPLES]

    try
    {
		dataModule iMan = new dataModule();
		String value, encPasswd;

		iMan.open("jdbc", "jdbc:oracle:thin:@carver.npac.syr.edu:1521:europe", "hyunkim", "hyunkim");
		
		iMan.addObject( "user", "Hyun" );
		iMan.setValue( "user", "Hyun", "e-mail", "hkim@npac.syr.edu" );
		iMan.setValue( "user", "Hyun", "password", "passpassme" );

		value = iMan.getValue( "user", "Hyun", "e-mail" );
		System.out.println( "Hyun's email: " + value );

        // Password Maching Part
        //
        // use the static method, 'passwordOK' in PasswdManager.java
        // Assume we read the user's passwod from the consol, say 'myPasswd'
        //
		encPasswd = iMan.getValue( "user", "Hyun", "password" );    // the return value is encripted only for password
		if ( PasswdManager.passwordOK( myPasswd, encPasswd ) )
		{
		    // password matched
		}
		else
		{
		    // password not matched
		}

        iMan.removeKey( "user", "Hyun", "e-mail" );
		iMan.removeObject( "user", "Tommy" );
		
        Enumeration e = iMan.getObjectKeys( "user", "Hyun" );   
		e = iMan.getObjects( "user" );      // get the list of all users
		
		iMan.update();  // save the changes
    }
    catch ( Exception e )
    {
    }


(2) ModuleFactory.java

	- Construct an instance of the specific class depending on the protocol

(3) dataAccess.java

	- Interface for the protocol-specific implemetation

(4) fileModule.java

	- Specific implementation for accessing data in the file
	- implements dataAccess interface

(5) jdbcModule.java

	- Specific implementation for accessing data in the database
	- implements dataAccess interface
	- "createtables.sql" defines the table scheme

(6) httpModule.java

	- Specific implementation for accessing data in the web server
	- implements dataAccess interface
	- not allowed to use some writing functional methods 
	  (such as setValue, removeKey, addUser and removeUser)

(7) ldapModule.java

	- currently suspended
	- Specific implementation for accessing data in the LDAP server
	- implements dataAccess interfade