The capabilities of cell phones increased dramatically in the last few years. While in the old days most mobile phones were primarily used to make phone calls, modern smart-phones are mostly all-round devices. With the possibility of accessing the Internet and the availability of various sensors (e.g. location or noise), mobile applications have become interactive and flexible. The trend towards location-based services and context-awareness allows applications to react on their surroundings and to behave intuitively towards the user.

For developers, context-awareness can be both a blessing and a curse. While the mobile operating systems iPhone OS and Android come with relatively good sensor-support, the vast majority of devices deal with Java ME’s basic and heterogeneous sensor functionalities.

The Aware Context API (ACAPI) aims to bridge this gap by providing a framework for building context aware applications for mobile devices based on Java ME. In this article, I’d like to introduce ACAPI, its structure and usage briefly. Please feel free to comment.

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In the last few years, the importance of the Internet has risen constantly and made it indispensable for businesses and most individuals to be on-line around the clock. One of the greatest drivers of this development was and still is the shift of the traditional one-to-many Web to an advanced, participatory version of the Word Wide Web. Rather than only making editorial information accessible to many users, the Web 2.0 encourages participation and enables user generated contributions. Leveraging this new paradigm, services like Flickr, Facebook, or Twitter have become very prominent examples for this development.

An essential part of this evolution, but mostly hidden to the end-consumer, is the set of tools that enable these large scale applications. Cloud computing is a relatively new technology that serves as underlying architecture for most of these platforms. By providing virtualized computing resources as a service in a pay-as-you-go manner, cloud computing enables new business models and cost effective resource usage. Instead of having to maintain their own data center, companies can concentrate on their core business and purchase resources when needed. Especially when combining a privately maintained virtual infrastructure with publicly accessible clouds in a hybrid cloud, the technology can open up new opportunities for businesses and help consolidating resources.
However, since cloud computing is a very new term, there are as many definitions of its components as there are opinions about its usefulness. Most of the corresponding technologies are only a few years old and the toolkits lack of maturity and interoperability.

This article introduces the basic concepts of cloud computing and discusses the technical requirements for setting up a hybrid cloud. It briefly looks into security concerns and outlines the status quo of current cloud technologies. In particular, it evaluates several existing cloud toolkits regarding its requirements, occurring problems and interoperability.

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WordPress is a very popular open-source blog software and is used widely throughout the Internet. However, with great success comes great attack potential: like any other wide spread open-source software, WordPress is target for frequent hacking attacks and spam-bots. All the more important is it to always update the distribution to the latest release.

As Debian/Ubuntu user, I am spoiled when it comes to update management: apt-get updates most of my software, and apticron notifies me when updates are available. For WordPress however, the packaged versions of Debian/Ubuntu are really old and less adjustable which unfortunately makes a manual installation inevitable. While there are several automated WordPress update mechanisms out there, I couldn’t find a simple notify-on-update tool.

This post introduces the WordPress Update Notifier (WP-UN), a simple script that frequently compares the installed WordPress version with the latest available one. If a new version is available, it sends an e-mail to a given address.

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Greylisting is a very efficient technique for fighting spam and can reduce the spam messages in your mailbox by more than 90%. It uses the fact that most spammers only try delivering their spam-mails once, whereas real mail transfer agents (such as the ones regular e-mail service providers are using) try delivering each message up to 4-5 days before they give up.

I have always wondered why most ESPs don’t offer greylisting for their mailboxes, but only rely on less effective and resource-hungry post-retrieval filter methods. Unfortunately, my e-mail provider is one of them so that I get at least a couple of spam mails a day …

Luckily, it is very easy to set up your own mail relay with greylisting support, i.e. a mail server that simply forwards the mail to your real provider once it passes the greylist-filter.

This little tutorial describes how to set up Postfix and SQLgrey as mail relay.

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