CONVID-19 coronavirus quarantine. A chance to promote e-conferences.

The quarantine that has been imposed to many parts of the world due to the spread of the CONVID-19 virus creates a lot of problems in transportation and in events like conferences. This may be a chance to reconsider the way that scientific conferences are organized. Although modern technologies of teleconferencing are used in a wide scale in education they are not used in conferences. So in parts of the world were the organization of gatherings is nowadays impossible, conferences have to be canceled.
A good alternative in all these trouble is simply teleconferencing, probably including an archive of video presentations and lectures. But if the scientific community will ever move to this direction there will be more benefits than just dealing with a temporary uncomfortable situation. Promoting teleconferencing and establishing a new type of e-conferences will make conferences open to a wider audience, not just to those people that make it to attend the event. Even without the quarantine, traveling to other countries and continents to attend a conference is not always an easy case and for many people is a difficult issue.
The demand for open science and data should not be restricted to the free dissemination of papers and preprints. In an era were multimedia flood the web and MOOCs are the latest trend in education, conferences should follow the same direction and become open platforms for exchanging ideas and interesting results in global scale.

Continuum Hypothesis and Uncountability

After setting the foundation on set theory by working on number sets and proving that the set R of real numbers is larger than the set N of natural numbers, Georg Cantor started working on a puzzling issue that was later called the Continuum Hypothesis. This deals with the following question “Is there a set of cardinality larger that set N and smaller that set R (the continuum)?”
Cantor believed that the answer to the question is negative but he did not managed to prove it and no one else did. So 150 years later this belief is formed as a hypothesis and it is still open, for most people.
Perhaps the most complete article on the hypothesis may be found here, it explains in details the whole issue its implications and the progress so far.
Researchers mainly use logic and axiomatic set theory on their attempts to prove the hypothesis. The research efforts focus on applications of the Zermelo-Fraenkel axioms with the axiom of choice; known as ZFC axiomatic system. The problem on this approach is that the hypothesis has been proven by Gödel and Cohen to be independent of ZFC. Since then, the scientific community has been divided in two parts. Scientists like Cohen believed that independence imply undecidability and the hypothesis has no answer. Others, like Gödel, believed that the ZFC system is not appropriate of resolving the hypothesis and some new system of axioms should be adopted.
This post is about some remarks that I have about the hypothesis and the ZFC application on it. The belief that ZFC independence results undecidability clearly implies that the ZFC system is universal on the sense that the properties of every possible set may be effectively described by the system. As ZFC is an axiomatic system and some of its axioms rely on intuition its universality should not be taken for granted.
For instance, the well-ordering theorem that is equivalent to the axiom of choice states that in every non-empty set there is one least element based on some property of the set. If we consider a set of uncomputable numbers how can we claim that any element of the set is the least element? It would be fruitful to investigate new axiomatic systems or try to provide stronger evidence about the validity of the currently used axioms.
Now let us suppose that the hypothesis is false and there is set H the cardinality of which lays between N and R. Set H is uncountable and its elements are uncomputable.
Set H is uncountable as it is larger than N. Considering the Turing machine model as a universal model of computation and as the set of all Turing machines is countable there are more elements in H than Turing machines so there are elements of H that do not correspond to a Turing machine and as a result they are uncomputable. There are uncomputable numbers in R as well and these considerations imply that a system or a theory that could be used to prove or disprove the existence of H should be able to handle uncomputable numbers and their properties.

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.

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.

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