Step 39 – Resolving Resource Dependencies

This is the new routine that I’m going to use to resolve the resource dependencies in the package manifest file.

function resolveIMSManifestDependencies($identifier) {

  global $resourceData;

  $files = $resourceData[$identifier]['files'];

  $dependencies = $resourceData[$identifier]['dependencies'];
  if (is_array($dependencies)) {
    foreach ($dependencies as $d => $dependencyidentifier) {
      $files = array_merge($files,resolveIMSManifestDependencies($dependencyidentifier));
      unset($resourceData[$identifier]['dependencies'][$d]); 
    }
    $files = array_unique($files);
  }

  return $files;

}

Here’s what I’m doing – line-by-line:

• Line 1: The function takes a resource identifier as its argument.
   
• Line 3: I’m going to process the data that I’ve stored in the $resourceData array, so I make it a global variable. I’ll have to do the same in the readIMSManifestFile() function, but more of that later.
   
• Line 5: I read the existing list of files for this resource (see line 1) into an array. I’ll be updating this as I go through the function.
   
• Line 7: I read the dependency information for this resource into an array called $dependencies.
   
• Lines 8 through 14: I loop through each of the dependencies for this resource.
   
• Line 10: This is the line that does the hard work. What I do is to merge together my existing ‘files’ array with a new ‘files’ array that I create by recursively calling the resolveIMSManifestDependencies() for each dependency (and any of its dependencies).
   
• Line 11: Since I’ve resolved this dependency (and any of its dependencies), I unset the dependency data in the $resourceData array so that I don’t process it again.
   
• Line 13: I eliminate any duplicate entries in the ‘files’ array.
   
• Line 16: I return the ‘files’ array to the calling program.
   

Now I have to modify the readIMSManifestFile() function so that it looks like this.

function readIMSManifestFile($manifestfile) {

  // PREPARATIONS

  // central array for resource data
  global $resourceData;

  // load the imsmanifest.xml file
  $xmlfile = new DomDocument;
  $xmlfile->preserveWhiteSpace = FALSE;
  $xmlfile->load($manifestfile);

  // adlcp namespace
  $manifest = $xmlfile->getElementsByTagName('manifest');
  $adlcp = $manifest->item(0)->getAttribute('xmlns:adlcp');

  // READ THE RESOURCES LIST

  // array to store the results
  $resourceData = array();

  // get the list of resource element
  $resourceList = $xmlfile->getElementsByTagName('resource');

  $r = 0;
  foreach ($resourceList as $rtemp) {

    // decode the resource attributes
    $identifier = $resourceList->item($r)->getAttribute('identifier');
    $resourceData[$identifier]['type'] = $resourceList->item($r)->getAttribute('type');
    $resourceData[$identifier]['scormtype'] = $resourceList->item($r)->getAttribute('adlcp:scormtype');
    $resourceData[$identifier]['href'] = $resourceList->item($r)->getAttribute('href');

    // list of files
    $fileList = $resourceList->item($r)->getElementsByTagName('file');

    $f = 0;
    foreach ($fileList as $ftemp) {
      $resourceData[$identifier]['files'][$f] =  $fileList->item($f)->getAttribute('href');
      $f++;
    }

    // list of dependencies
    $dependencyList = $resourceList->item($r)->getElementsByTagName('dependency');

    $d = 0;
    foreach ($dependencyList as $dtemp) {
      $resourceData[$identifier]['dependencies'][$d] =  $dependencyList->item($d)->getAttribute('identifierref');
      $d++;
    }

    $r++;

  }

  // resolve resource dependencies to create the file lists for each resource
  foreach ($resourceData as $identifier => $resource) {
    $resourceData[$identifier]['files'] = resolveIMSManifestDependencies($identifier);
  }

  // READ THE ITEMS LIST
 
  // PROCESS THE ITEMS LIST TO FIND SCOS
 
  // RETURN RESULTS

}

The changes are:

• Line 6: I make the $resourceData array – a working array where I store all of the information as I process it – global so that it’s accessible to the resolveIMSManifestDependencies() function.
   
• Lines 44 to 49: I create a list of dependencies for each resource, and save it into the $resourceData array.
   
• Lines 56 to 59: After I’ve read all of the data for the resources (the loop finishes on line 54) I loop through the list of resources again and resolve all of the dependencies by calling resolveIMSManifestDependencies() as I described above.
   

Now that I’ve read all of the resources data, I’m going to read the items data. That will be my next post.