Though at the moment I can’t reveal much about it (not that it’s classified or anything, but it’s not finished, nor presented to the “client” yet), I’ll show some pics of the CAVE physical installation and will keep posting on how this advances until we complete it.

[imageflow id="11"]

Problem/Error: Trying to obtain a responseXML object from a Mediawiki API query results in a null pointer. A responseText object, however, returns the HTML text just fine.

Solution: What’s happening here is that Mediawiki API is responding to the AJAX request (GET or POST, it doesn’t matter) using the default format, namely, a plain text, HTML formatted version of the original XML. To obtain an XML object (or any other kind of object that Mediawiki knows, for that matter e.g. JSON), you have to explicitely tell the API in which format you require the answer. For example:

The following code shows a query requesting information about the main page of a mediawiki installation.

//JS method called from an "onClick" event
function getMainPageInfo()
{
   //start by getting an XMLHTTP object
   xmlHttp=GetXmlHttpObject();

   //make a simple check of AJAX support
   if (xmlHttp==null){
     alert ("Your browser does not support AJAX!");
     return;
   }

   //Modify the path with your own info
   var url="/mediawiki/api.php";
   var params="action=query&titles=Main%20Page&format=xml";

   //Send the proper header information along with the request
   xmlHttp.onreadystatechange=paintMediawikiAnswer;
   xmlHttp.open("POST", url, true);
   xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
   xmlHttp.setRequestHeader("Content-length", params.length);
   xmlHttp.setRequestHeader("Connection", "close");
   xmlHttp.send(params);
}

//Get the answer and paint it to a <span> element
function paintMediawikiAnswer()
{
   if (xmlHttp.readyState == 4) {
      //get the XML tree
      xmlDoc = xmlHttp.responseXML.documentElement;
      switch (xmlHttp.status) {
         // Page-not-found error
         case 404:
            alert('Error: Not Found. The requested URL could not be found.');
            break;
         default:
            // Call the desired result function
            elementRetrieved=xmlDoc.getElementsByTagName("page");
            alert("Pages received: "+elementRetrieved.length);
            break;
      }
   }
}

Today I got XAMPP for Linux (formerly known as LAMPP) finally up and running. Here are some caveats that I encountered while completing the installation:

1. Though the “installation” of XAMPP is supposed to be as simple as “uncompress and run” it actually needs you to take care of the right permissions for some of the folders in the installation directory. Unless you are a security freak, the best thing you can do is the following:
   • chmod -R 644 /opt/lampp (assumming that your installation directory is actually “/opt”)
   • chmod -R 755 /opt/lamp/htdocs (to avoid some problems with the stuff you will install inside later on)
2. If after doing the pervious step you ever encounter the error “ERROR 2002: Can’t connect to local MySQL server through socket” when you try to start phpMyAdmin, you need to go to the folder phpMyAdmin in the XAMPP installation (/opt/lamp/phpmyadmin) and change the permissions of the file config.inc.php to “644″ (chmod 644 /opt/lampp/phpmyadmin/config.inc.php). I admit that this is a weird fix, but for some reason phpMyAdmin doesn’t like other permissions than this when telling XAMPP to connect to the database and produces an even weirder error which is totally unrelated to the actual permission problem…

Anyway, i’ll keep posting some other tips I find…

Competing for the prize were 11 candidates from the 3 Universities of Applied Sciences in the Köln-Bonn area. Unfortunately I didn’t win the first prize, but it was already an honor to be the only foreigner nominated to the prize, and actually had the chance to present my work to an elite group of engineers of the region.

The award ceremony took place at the Technologie Park in Bergisch-Gladbach (East of Köln) on the 1st. of December.

[Show as slideshow]

[View with PicLens]

As soon as I have some more time, I will put more interesting stuff out there…