Friday 17 August 2018

A paper on defining and modeling context-awareness

A paper I wrote a few months ago is just published.

"On defining and modeling context-awareness", International Journal of Pervasive Computing and Communications, (2018), https://doi.org/10.1108/IJPCC-D-18-00003

Also there is an Author Accepted Manuscript pdf (or else preprint).

The paper presents a methodology on defining and modeling context-aware systems. These are systems that detect their environment in order to operate and interact with users and other systems. The methodology is based on a computational model, named Networked Turing Machine, that extends the capabilities of classical Turing machines by enclosing interaction on their operation and supports modeling of interactive and distributed computation. Then using this computational model the notion of context-aware systems is defined.
One of the motives of writing this paper is discussing context-awareness using the theory of computation. It is common in the literature of the field to talk about context-awareness using plain language and developing definitions and theoretical frameworks that avoid mathematical definitions. This habit does not allow the connection of any context-aware framework with the rich and valuable literature of computing theory and with fields like computational complexity.
The methodology in the paper describes a useful way of developing models that describe distributed systems focusing on their structure.
A case study is also presented. A model that describes the structure of the web application WMS Map viewer is developed using the methodology of the paper.

Saturday 5 May 2018

Hacking geoserver.war

One easy and efficient way to setup geoserver is as a standalone servlet on an application server like Apache Tomcat. Geoserver is released in many formats one of them is as a web archive (.war file) which contains all the necessary application and configuration files to run geoserver. This is a particularly convenient way to setup geoserver as application servers are available on cloud platforms like Amazon AWS and Azure with a simple deployment procedures and affordable prices, even free in many cases.
There is only one disadvantage in this approach. The .war file contains files with default configurations and they may not be modified during the execution of the application. So every time you need to install geoserver it is necessary to set up the configuration from scratch; nothing is saved on the web archive. This is quite problematic as you will have to setup geoserver from scratch even after a simple reboot of Tomcat or the cloud container. Luckily you may easily hack it.
Web archives .war files are simple zip files, changing their extension or opening the file on a zipping application is enough to reveal their content. As far as it concerns the configuration files of geoserver they are the same on all formats for all platforms. So this is what to do.
Download the platform independent platform binary version  and run the application on your local machine. Set up the application as you will, setup map layers, wms layers, styles and anything else. Don’t forget to change the passwords and security settings.
Unzip and delete the files from the data directory of the web archive. Then copy the files from the "data_dir" directory of the locally installed application to the "data" directory of the web archive. Zip again the web archive version and change the extension back to .war. You are fine.
Deploying the modified .war file on cloud or on an application server will get you a working geoserver with the setting you have applied locally as default settings.

Wednesday 14 March 2018

An interestng lecture of Steven Hawking about randomness

There are some scientists that besides their talent in discovering the mysteries of the universe also have a talent in talking in plain and comprehensive language about them.
Steven Hawking definitely had both talents. This lecture of his about randomness is an example.
http://www.hawking.org.uk/does-god-play-dice.html

-RIP