Step 60 – Supported Data Elements

One of the things that has caught me out in a couple of recent cases is that the SCORM standard makes SCO developers rely on error codes to determine whether or not certain elements are supported. I describe one specific example in an earlier post – Step 54 – Error Handling.

In a sensible system, the initialization process would provide the SCO with a complete list of supported elements so that it wouldn’t have to go through all this rigmarole. But that’s too much to hope for, so I need a simple way to check whether a data element is supported or not, and I’ll also need to check whether it’s readable and/or writeable.

I’m going to start with my favorite weapon of choice – a JavaScript object (associative array for the perl and PHP fans). Here it is:

var dataElements = new Object();

dataElements['cmi.core._children'] = 'RO';

dataElements['cmi.core.student_id'] = 'RO';
dataElements['cmi.core.student_name'] = 'RO';

dataElements['cmi.core.lesson_location'] = 'RW';
dataElements['cmi.core.credit'] = 'RO';
dataElements['cmi.core.lesson_status'] = 'RW';
dataElements['cmi.core.entry'] = 'RO';
dataElements['cmi.core.exit'] = 'WO';

dataElements['cmi.core.score._children'] = 'RO';
dataElements['cmi.core.score.raw'] = 'RW';
dataElements['cmi.core.score.max'] = 'RW';
dataElements['cmi.core.score.min'] = 'RW';

dataElements['cmi.core.total_time'] = 'RO';
dataElements['cmi.core.session_time'] = 'WO';

dataElements['cmi.suspend_data'] = 'RW';
dataElements['cmi.launch_data'] = 'RO';

dataElements['cmi.comments'] = 'RW';
dataElements['cmi.comments_from_lms'] = 'RO';

This is nothing more than a list of the supported elements with their read/write status.

Then, to make life a little neater when I come to plug this into the actual code, I’m going to define a simple little function:

function isSupported(dataElementName) {

  // flags
  dataElementSupported = false;
  dataElementRead = false;
  dataElementWrite = false;

  // if the data element is in the list of supported elements
  if (dataElementName in dataElements) {

    rights = dataElements[dataElementName];
    dataElementSupported = true;

    if ( (rights == 'RW') || (rights == 'RO') ) { dataElementRead = true; }
    if ( (rights == 'RW') || (rights == 'WO') ) { dataElementWrite = true; }

  }

  return dataElementSupported;

}

This function simply sets three flags that are available to the LMSSetValue and LMSGetValue functions so that they can test the SCO-supplied input, and generate appropriate error codes.

Next, I’m going to add this to the LMSSetValue and LMSGetValue functions.