Turingmaschinen

Merke

Mit keinem heutigen Rechner und keiner heutigen Programmiersprachen können Funktionen berechnet werden, die nicht auch mit einer Turingmaschine berechnet werden können.

Die Turingmaschine ist ein allgemeines Modell für die Berechenbarkeit.

Entscheidbarkeit

Ein Problem P ist entscheidbar, wenn es einen Algorithmus gibt, der für P mit Ja oder Nein beantwortet werden kann.

Unentdcheidbare Probleme

Z.B. Kommt eine bestimmte Ziffernfolge im Nachkommsteil von Pi vor?

RDF Primer

> reading the RDF Primer @ http://www.w3.org/TR/rdf-primer/

This Primer is so long - I couldn't make it to the end of the document, yet. The more I read the more complex this whole topic seem to become.

Till paragraph 2.4 it explains the basic structure of RDF. Data or any information is formed as triples, separated in a predicate, an subject and an object. When you are not using any abbreviations it would look like this:

<http://example.de> <http://information.de/what-type-of/data/> <http://example.de/data/value/>

The first defines let's say the "thing" we want to bind information to. The second defines what type of information we are saving here. And the third is the value.  The value could also be a literal string like "value", instead of a resource to the value.

Fortunately this can be made shorter. You can define abbreviations for long URIrefs (in this case the URLs). These are called QNames (qualified names). So you could say "ex:" stands from now on for "http://example.de". Then you can reference it like this:

ex:index.html info:data exdata:value

(where info = "http://information.de/what-type-of/" and exdata = "http://example.de/data/") When you use QNames you don't need the brackets < and > around the resources. Just when the resource is a URI than you have to wrap them with brackets.

Basically you could define your own dictionary (the "abbreviations") with your own meaning for what is what. There are no restrictions from RDF. But if everybody defines his "own crap" it would get quickly very messy in the web and no one (especially no software) would understand what is meant. So it is considered best practise to use already well defined dictionaries, like this one http://purl.org/dc/elements/1.1/ . This way everything is more clean and if you find an RDF document referencing to this dict you can be sure what it is about. Of course you could also define your own one and reference to it - but why try to invent the wheel again 😉

Learning Diary

A learning diary - or as I call it here, a journal - is a good possibility to review what you've learned. Just by writing about your thoughts to a specific topic you are thinking about everything again and by that are somehow forced to remember. Since the current semester is almost over, I can evaluate my learning diary writing now.

I must admit that it was quite difficult to write something regularly. And this is mainly because it is quite time consuming, especially in the beginning. Thinking of, that I would do this for every course I have during the semester (that was the plan at the beginning), I would be quite occupied with writing. But again, this is a matter of practice. I wasn't really used to do this kind of writing, so I had some difficulties with my first entries. Now, at the end of the semester after I wrote some entries (but still not as much as I wanted to), it's slowly becoming easier.

I actually like this and I will try to keep on writing this journal during the rest of my master studies. Especially when using wordpress this might be very helpful for me. For example using hypertext to connect old and new knowledge looks interesting to me. Also the possibility to go back to old entries and add or alter them is great.

I used this of course with my computer. I logged in and wrote some entries. But I also used this with my BlackBerry. This is great when I am on the go. I can write some entries while I am waiting for public transport and this way use the time for something meaningful.

Writing an entry to my learning diary on my BlackBerry

E-Learning

Actually I like e-learning. I have a quite big internet affinity. So of course I like using my computer and the internet for learning.
But I have a problem how e-learning is done by many companies, organisations and different people. Like I already mentioned in the mobile learning entry, the whole e-learning area with all its subsets is so focused on technology. Of course technology is the key to e-learning. It makes it possible. But it is very often so bad made that it is just not useful. Which in the end makes e-learning useless.
This is a issue the e-learning area has to fight with and hopefully "they" will find ways to make everything better. Until then I guess, e-learning will take make up just a small part in my learning.