There are basically three ways to formally define a language through its’ semantics: (a) operational – through algorithm, (b) denotational – through mathematical equations and objects , and (c) axiomatic – through logic to prove the correctness of a program.

Operational Semantics

The purpose of this approach is to describe how a computation is performed step-by-step. For instance, in a Java program, the Java Virtual Machine (JVM) does that for us. This type of semantics is very familiar especially those who read how-to books of a programming language since we can understand the operational semantics of a program using pseudocode.

For instance, in Java:

if (condition) {
doSomething1();
} else {
doSomething2();
}

Its’ operational sematics:

if condition = true goto doSomething1()
else goto doSomething2()

Given that condition is a boolean that can have a value of either true or false.

Denotational Semantics

Denotational Semantics is an approach that describes the meaning (denotation) of a program using mathematical objects. Usually, they are functions of some sort.

Let Σ be the set of all program states in a programming language. A boolean expression Bexp can be described in a denotation as:

B: Bexp → (Σ → {true, false})

A variable that has been assigned as a boolean can only have values true or false, and the whole assignment expression means that it can only be true or false. The syntactic equivalent of this expression depends on the programming language (i.e. in Java it is boolean b = true; or boolean b = false;)

Axiomatic Semantics

Axiomatic Semantics asserts the relation will always be true for an input and output interface in a program, each time the program is executed.

The semantic formula is of the form

{P} S {Q}

where P is a a pre-condition, S is the command or the control structure, and Q is the post-condition. It is read as the statement S is correct with respect to pre-condition P and post-condition Q. If P is satisfied and S halts, S terminates in a state where assertion Q is satisfied.

For instance, we would like to prove that:

{x = X ∧ y = Y ∧ z = Z} min(X, Y, Z) {min = min(X, Y, Z)}

So,

{x = X ∧ y = Y ∧ z = Z}
min = x; {min = X}
if (min > y) {x = X ∧ y = Y ∧ z = Z ∧ X > Y}
min = y;
{min = Y}
if (min > z) {x = X ∧ y = Y ∧ z = Z ∧ (X > Z ∨ Y > Z)}
min = z;
{min = Z}
{min = min(X, Y, Z)}

Right now I am taking two subjects – IS201: Computer Ethics, and IS214: Principles of Programming Languages. I’ve started IS201 sometime this week, while IS214′s course website hasn’t been opened. I hope next week I’ll start working on that course.

Yes, I’m studying while working.

I really am enjoying this new mode of learning for me. I’ve been learning through the net a lot for the past few years, and it is only now that I’ve been a DE student. I’m meeting new people (online or otherwise), and I am certainly pleased. But I can’t judge much since it’s only been like a week. But so far, so good.

To end this post, I would like to share an inspiring quotation from Jack Canfield about self-esteem and believing in oneself:

Self-esteem is a huge piece of my work. You have to believe it’s possible and believe in yourself. Because after you’ve decided what you want, you have to believe it’s possible, and possible for you, not just for other people. Then you need to seek out models, mentors, and coaches.

Total Sleeping Hours: 8 hours (23:30-07:30). Yay!

Night 3: 16 February 2010 – 18:30: Logged off early to have a walk in the park with my officemate. I had to unwind due to pressure at work and some personal stuff going on. I had to literally let things off my chest. That gave me enough strength to drive myself home, do errands, finally unpack,  and prepare myself to sleep. Besides, I had to go to QC the next morning to do some errands.

Total Sleeping Hours: 7 hours (00:30-07:30). Yay!

I finally had a wake-up call when I’ve been acting really weird lately, even close to depression. I NEED MY EFFIN’ SLEEP!

Night 1: 14 February 2010 – 19:57. I bought Sleepasil to aid my sleeping. I always have this habit of thinking A LOT before going to sleep. I always find myself waking up in the wee hours of morning, and having a hard time going back to sleep after. 10 minutes after taking Sleepasil, I felt really sleepy so I switch off my PC, and went straight to bed. Good, right? But after an hour (9PM) some kid banged the door that woke me up — JUST to get her toothpaste from our bathroom inside the room. Now I know why my mom always gets mad at me whenever I knock her door whenever she’s sleeping. I swear, I’ll never wake up my Mom from her sleep again.

Anyway, I tried going back to sleep for an hour but to no avail, so I went online, replied to a few stuff on Facebook, checked my email, read some feeds, and finally went back to sleep at almost 12MN. Woke up at 5AM the next day:

Total sleeping hours: 1 + 5 hours = 6 hours (FAIL!)

The thing is, I realized I miss writing long paragraphs, and so I decided to bring this blog back to life.

In case you’re interested, here’s my Tumblr.

Long post coming in a few days.

First offer was for 2 years: I accepted. I was terribly confused since I really want to study for Graduate School next year, but didn’t want to pass up an opportunity to work in Japan. But I failed on the interview since I was really bad in conversational Japanese, and I wasn’t really prepared.

Second offer was good for 3 years. I declined since it’s too long for me. Besides, I had other plans. After I declined I decided to stay here in the Philippines in the meantime and study for Graduate Studies instead. I gave myself two years to finish the degree. The past few weeks were spent thinking about my thesis – and I decided to continue what I was working on when I was still an undergrad – Crime Profiling in the Philippines, which incorporates all that I will learn in Grad School. I also decided to focus on Web Science, since it has been my interest since time immemorial.

Yesterday, I got an offer again: I’ll be in Japan for a year. That was perfect for me, except that they want me to leave by January. While I was being asked, I decided to move my studies by 2011. That will be perfect since my target is to finish my degree by 29 years old. (Yes, I have a deadline LOL.) I asked what are the other options, since I have plans for February and April. They told me that my other teammates are scheduled to leave by April – and they want me to go to Japan first. I requested to exchange with my other teammate who is scheduled to leave on April – that means he’ll leave this January, and I’ll leave in April with my other teammate.

Personally, I feel really bad. I’ve been spending my energy the past few weeks thinking about graduate school, but at the same time I want to experience working abroad.

BUT, I’ve been thinking a lot about the Google screening I just had the past few months. I didn’t make it on my technical interview – too bad, huh. I’d like to think it’s because I was both nervous and distraught emotionally during the time of the technical interview since my father died the morning before – but I know I’m just making an excuse. The questions were really interesting, and that Google experience inspired me to study more and strive to get better in computing – particularly Web Science.

If I go to Japan:

April 2010-2011: Japan

May 2011-2013: Philippines while finishing Master in Info Systems (UPOU)

Pros:

• working in another country
• able to save more
• nice place, etc.

Cons:

• stuck with one technology for a year (I can study on my free time, but God knows experience counts a lot)
• must pass up other opportunities (i.e. surprise interview from Google)
• homesick (can deal with it since I’m used to it already)

If I stay here/Original Plan:

June 2010-March 2011: Part-time student – Master in Computer Science (UP Dil)

June 2011-March 2012: Full-time student- Master in Computer Science (UP Dil)

Pros:

• studying what I love
• learning more
• more exposure to research
• more opportunities after grad school
• more opportunities to be more exposed to FOSS
• more free time, yay!

Cons:

• lesser money (yes I can do part-time)
• might get bored (still not sure, it’s just a fear)
• might not finish grad school (still not sure, it’s just a fear)

Grad School wins big time.

I’ve been thinking a whole lot about where to study, what I should focus on during my studies, and what my thesis will be about.

I’m looking for a university which focuses on Web Science, which I’m very interested in. It’s a fairly young discipline which integrates Computer Science, Artificial Intelligence, Business, Law, Sociology, Psychology, etc. that shapes the future of the web.

I’m also keen on continuing my research work on crime profiling in the Philippines, or work on something else for my thesis.

Right now, I’m just plain amazed how Facebook turned into a tool for information dissemination about the typhoon Peping which wreck havoc in Metro Manila.

MyGP, which I am part of, is also working on projects that might benefit a lot of people in the long run.

It’s web science at work – and I’m interested to be of help in shaping the Filipino web.

I stopped watching TV way back 2006, thinking I’d rather be online, pursue my passions in programming, development, and FOSS, meet new people, and download Japanese Drama shows or other interesting programs when I’m bored.

It’s not that I NEVER watched TV since 2006. Of course I co-watch with my friends and family whenever I visit their homes, but it’s not as if I volunteered myself to open the TV and switch to my favorite channel.

Last weekend, when our internet cable operator failed to bill us last month, and thought we didn’t pay up, our internet was cut down. While waiting for the internet to get back, I decided to watch TV instead with my nephew downstairs. I realized I missed watching Discovery Channel, etc.

I did it again yesterday when we were resting for a while at my co-AS2 alumni’s office at University of the Philippines Open University (UPOU) after manning the UPOU (and International Open Source Network – IOSN – booth, for a few minutes) at the Software Freedom Day 2009 at UP National Computer Center (NCC). I watched E! Channel without feeling guilty or feeling stupid. Haha.

It definitely feels good to watch TV (voluntarily) again after some time.

BigDecimal one = new BigDecimal("1");
BigDecimal oneWithDecimal = new BigDecimal("1.25");
BigDecimal result = one.divide(oneWithDecimal);

This will throw an arithmetic exception, since as I’ve read from the Java API,

BigDecimal divide(BigDecimal divisor)

Returns a BigDecimal whose value is (this / divisor), and whose preferred scale is (this.scale() - divisor.scale()); if the exact quotient cannot be represented (because it has a non-terminating decimal expansion) an ArithmeticException is thrown.

This is to say that the example above will throw an ArithmeticException since the dividend and the divisor have different scales.

The code below should work.

one.divide(oneWithDecimal, 3, RoundingMode.HALF_UP);

めんどくさい。(Tedious.)