database style data structure?

From: dmb000006 (dmb000006_at_hotmail.com)
Date: 03/26/04 

Date: 26 Mar 2004 03:57:22 -0800

Hello,

I have a database style data structure, each record has several
fields.

I would like to create a nested data structure that would let me
'query' the data on the value of certain fields.

I did this by making the following type of data...

Sample PDB data...

ATOM 72 C ARG L 9 41.592 23.248 98.505 1.00 34.28
      C
ATOM 73 O ARG L 9 42.467 23.303 97.634 1.00 33.66
      O
ATOM 74 CB ARG L 9 40.542 25.445 99.063 1.00 32.51
      C
ATOM 75 CG ARG L 9 40.415 26.641 99.989 1.00 30.92
      C
ATOM 76 CD ARG L 9 39.771 27.823 99.291 0.00 47.64
      C
ATOM 77 NE ARG L 9 38.331 27.672 99.123 0.00 67.84
      N

package PDB;

our $pdbTemplate
  = 'x6 A5 x1 A4 A1 A3 x1 A1 A4 A1 x3 A8 A8 A8 A6 A6 x6';

our @pdbDescriptive
  = qw( serial name altLoc resName chainID resSeq iCode x y z
occupancy tempFactor segID element charge );

our @pdbDataIndex
  = qw( serial name altLoc resName chainID resSeq iCode );

sub readPDB {
  my $pdb = shift;
   
  unless (ref($pdb) eq "GLOB"){
    $pdb = openPDB($pdb);
  }
   
  # Data to return
  my %pdbData;
 
  while ( <$pdb> ){
    next unless /^ATOM|^HETATM/o;

    # Parse PDB file (see $pdbTemplate above)
    my @atom = unpack( $pdbTemplate, $_ );

    # Trim each value.
    foreach ( @atom ){ s/^\s+// };
     
    # Must be a better way? (to make a HASH).
    my %atom = map { $pdbDescriptive[$_], $atom[$_] } ( 0..$#atom );
     
    # Build up quite a complex data structure.
    foreach (@pdbDataIndex){
      push @{$pdbData{$_}{$atom{$_}}}, \%atom;
    } push @{$pdbData{'data'}}, \%atom;
  } return \%pdbData;
}

__END__

This lets me say...

use PDB;

my $data # Special data structure!
  = readPDB( $pdb ); # Would be good to use Fields;

my @chainIDs # Lookup 'chain' entries
  = sort keys %{ $data->{'chainID'} };

foreach my $chainID ( @chainIDs ){
  
  my @atoms # Use 'chain' entry to get at underlying
atoms.
    = @{ $data->{'chainID'}->{$chainID} };
  
  print "$chain\t". scalar(@atoms). "\n";
}

__END__

But I would like to go one step further and for each chain return each
residue, or for each residue return each chain etc... (i.e. recursive
data structure).

How can I do this?

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