The beta version of the latest Ubuntu, Hardy Heron 8.04, has been released. The official release will be on April 24th 2008.

Link | Ubuntu releases

One use of the lower-case Greek letter λ is a branch of mathematical logic called Lambda Calculus. It’s a formal system designed to research function definition, function application and recursion. Throughout the years, λ has been seen on many logos related with the functional programming. For example, the MIT Scheme’s logo represents a recursive shield with lambda:

We can see lambda on the functional programming language Haskell’s logo. Apart from lambda, we can see five other mathematical symbols, representing the Haskell’s functionality. These are their respective meanings:

-The right arrow (→): Transformation
-The universal quantification (∀): For all
-The double angle (≫): Free from disorder
-The double right arrow (⇒): Generality
-The double colon (::): Exactitude

A scheme-to-C compiler called Chicken has a logo that represents a lambda inside a hen silhouette.

CL-HTTP (Common Lisp Hypermedia Server) has a lambda symbol on its logo too.

More information | Xahlee

The first century starts at 0001-01-01 00:00:00 AD, although they did not know it at the time. This definition applies to all Gregorian calendar countries. There is no century number 0, you go from -1 to 1. If you disagree with this, please write your complaint to: Pope, Cathedral Saint-Peter of Roma, Vatican.

Seen on PostgreSQL Documentation

Since I started to build YouAre.com I knew that the scalability was an important matter to solve. Sometimes the scalability is more important for your pocket and for the success of your startup than originally thought. According to Google, a slow performance could cost you 20% of your revenue. If you are starting a new company, you ought to know that any savings in servers can accelerate the growth of your company. These costs include hardware, software, human resources and time (for many people the most appreciated resource). Apart from the monetary costs, it’s proved that half a second delay in page load time can kill a user’s satisfaction.

The scalability is a relative problem which depends on many things: the technology used, the fault tolerance and the availability of programming staff. Many people think that scalability=performance, and they are wrong as there are more aspects to be considered. For me, the scalability is to maintain the balance between the resources and the number of users, when the size of the problem increases. The size of the problem is the growth of the number of users and the resources. A graphic which represents a good scalability could be the following:

We can appreciate how well the growth of users (n) have been solved. The amount of required resources grows logarithmically.

Some good points for scalability that should be considered:

• Good database design: Normalize the database, select a suitable DBMS, consider the users’ necessities, …
• Search engines: Use a search engine for your application. Lucene is a very high-performance text search engine library. You can also consider Nutch or Solr, both based in Lucene but oriented to web applications. If you are finding some engine more basic take a look at Sphinx.
• The Keepalive problem: Enabling Keepalive for images and external files (such as CSS) is very good for clients, but bad for servers. Keeping Keepalive off we reduce a lot of the memory of the server. A good solution is to have separate images in a different server, getting the added benefit of higher browser concurrency with multiple hostnames (it will let you to load images in parallel). In YouAre, we are using Amazon Simple Storage Service to store our images.
• Cache: Cache as much of your dynamic content as possible Memcache could be a great option.
• Take care of your code: Take care of your code and it will take care of you
• Use GNU/Linux: GNU/Linux uses spare memory to cache files on disk. This means much faster I/O.

More information | Rico Mariani
More information | Shiflett
More information | No VC required

The XSL Cache extension is a mod of PHP’s XSL extension developed by the NYTimes. This extension caches the parsed XSL stylesheet representation in sites that constantly the same transform is applied. The code is already working with a few applications on the New York Times’ website.

The installation is very easy. Just run the following commands:

phpize
./configure --with-xslcache=
 –with-xsl-exsl-dir=</path><path to libexslt>
make
sudo make install
</path>

Then you have only to add the line extension=xslcache.so to php.ini file and restart the web server. I’ve been doing some tests with XSL Cache and I got good results. The following code shows how to load a stylesheet and then use it to transform a parsed XML document:

<?php
$xsltpath = '/home/harrisj/example.xsl';

$xslt = new xsltCache;
$xslt->importStyleSheet($xsltpath);
$xml = DOMDocument::loadXML($source_doc);
print $xslt->transformToXML($xml);
?>

Link | XSL Cache Project

The Spanish Ministery of Health and the Andalusian School of Public Health have developed a robot called Robin who is able to answer your questions about sexuality (diseases, information for children, …) and alcohol (risks, effects, suggests, …) through MSN Messenger. His answers can include graphics and other resources. You can add Robin at robin@msc.es. Robin’s main goal is providing information to young people about sex and alcohol. It’s a curious way of giving health information to young people. Robin uses a familiar language for boys and girls between 12 and 17 years old.

Link | El País

We are just at the beginning of the countdown for the new Ubuntu 8.04 Hardy Heron release. We will be able to enjoy the final version in 4 months. I’ve read at UbuntuLand a list of some new features of Hardy Heron. The following features are noteworthy:

• Auto Detection of Monitor Frequency
• Xorg 7.3 (This feature missed the Gutsy Gibbon deadline)
• Install on an existing filesystem without overwriting /home
• Better and more robust detection of hardware
• New default theme for Gnome (style, wallpapers, colours, …)
• Handling Full Disks
• Dual/Multi Monitor Support (Currently you have to manually tweak Ubuntu if you want to use more than one monitor)
• Apparmor Integration
• GDM Face Browser
• Deleting duplicate libraries

GNU Octave is a cross-platform Open Source alternative for the famous Matlab. Octave uses the same commands as Matlab and it’s an excellent free alternative. The new version 3.0 was released the past December 21st. The most significant changes have been the improvements of graphics (like controling the width of lines, RGB line colors are supported, the possibility of making a subplot and then use the print function to generate file with the plot, …), path handling and built-in variables. You can check out all the notable changes in the Octave official site.

The release of the new KDE 4 will match simultaneously with the development cycle of Kubuntu 8.04. As we’ve said before, Ubuntu 8.04 will be a LTS (Long Term Support) version. Jonathan Riddell sent an email to the Ubuntu MailList telling Kubuntu 8.04 will be released with the option of using either KDE 3.5 or KDE 4. The difference is Kubuntu 8.04 with KDE 4 will not be LTS. Anyway, people who keeps a KDE 3.5 release will receive the usual 18 months of support for that release.