Stephen on Software

Leaflet, ArcGIS Server Invalid SRS

2013-05-20T16:43:00.002+08:00

I encoutered some problems with ArcGIS Server and Leaflet WMS api. Namely its because the API sends the "srs" parameter to ArcGIS server with the value EPSG3857 while ArcGIS server expects EPSG4326.

Basically these EPSG values refers to the spatial reference of the maps in which they are drawn, they are what determines where exactly the position is when you say a certain location like 1N 103E.

How can you discover this error? You can use firebug to trap what URL calls the webpage is calling the WMS server, then you paste the URLs into a new window there should be an xml telling you the error if there is any, if not then a picture with the portion of the map as specified in the URL should be displayed.

Found the solution in Google Groups bascially you need to setup the map upfront by stating what spatial reference it should use.
e.g

var map=L.map('map',{crs:L.CRS.EPSG4326}).setView([51,0],13);

It's specified as a option to the map function.

Weblogic and Spring Log4jConfigListener [java.lang.IllegalStateException: Cannot set web app root system property when WAR file is not expanded]

2013-05-08T13:49:00.002+08:00

If you are using Weblogic and Spring's Log4JConfigListener you might encounter a problem when in your testing envrionment when you deploy from your IDE to your Weblogic instance it seems ok.

But when you package it into a war file and deploy it. You get an
[java.lang.IllegalStateException: Cannot set web app root system property when WAR file is not expanded].

This is due to the Log4JConfigListener requiring to look up the log4j.properties file and from a war file it can't do that.

You can either always deploy it in a exploded war file or simply adding the following to your weblogic.xml file.

true

This should solve the problem.

InfoQ: Scaling Pintrest

2013-05-01T06:56:00.001+08:00

Some things i learnt from the a InfoQ video about Scaling Pintrest.

1. Clustering is complicated

This changed my whole point of view about High Availability. The comment made about how your application is depending on some complicated algorithm for synchronising and making sure every node is in a correct state is bad because if anything goes wrong you will have a lot of trouble. Which is a problem with a lot of clustering solutions, they are complicated to setup and if anything goes wrong you have a hard time figuring out what's wrong, most of the time I just pray and reboot the servers hoping that everything works.

Compared that to Sharding where you know how your data is stored and partitioned (You wrote the algo). But the problem with Sharding is that your application will need to be smarter on how to find the data, perform joins and you need to have a robust plan for data migration. You will need to plan for future capacity when you are designing the Shard so you don't have to perform migration too often.

The video does show how they designed their sharding algo and considerations made.

2. Keep things simple in the technology stack

This has got to be the rule that everyone knows but damn hard to follow. The Pintrest guys started off with a complicated stack but eventually they settle down to well known technology in terms of maturity, stability and simplicity. They eventually just settled on MySQL, Redis and Memcache. Which are all well know and simple to understand systems.

3. Cache, Cache, Cache

For any large system, caching your reads is important for performance. (But you already know that :))

Agile Fluency

2012-12-27T09:42:00.000+08:00

Nice Article from Martin Flower (or more specifically by Diana Larsen and James Shore) on Agile Fluency.

Good read on how to agile teams should evolve

http://martinfowler.com/articles/agileFluency.html

HBase schema design

2012-06-18T10:26:00.000+08:00

The HBase reference documentation dosen't really say much about schema design and most of us coming from a relational back ground will need to change our way of thinking in order to swtich to a more column based kind of designs.

You need to look more at the types of queries that you will be needing to access your data rather that just nomarlise every thing to 3rd normal form as in traditional relational databases. And that itself might not be easy. I will be writing more as i try to design my current application's data base into a Hbase kind of design, and what are the challenges i find.

Below are some of the useful resources that helped me in understanding column based kind of designs.

http://ianvarley.com/coding/HBaseSchema_HBaseCon2012.pdf

http://traackit.blogspot.sg/2010/05/20090713-hbase-schema-design-case.html

Schema Design Guidelines and Case Studies
https://docs.google.com/viewer?a=v&q=cache:Oe0Kf9oQhO0J:india.paxcel.net:6060/LargeDataMatters/wp-content/uploads/2010/08/Schema-Design-Guidelines.doc+&hl=en&pid=bl&srcid=ADGEEShyf8WIXTdsWbYRTWWLHUgvYbWDa2AilTnm6xUWnaHDvpX6gARtzDNBx6GlsbE1hjdZoR3hYBYjk03zlwq8LLkA9VRYlLwihD4S75pxlMtitX640uwrQsOa0cC5K5JPGfhAfQIK&sig=AHIEtbR8TyqVgcc3WFGtpKWX7eZOZBpnFQ&pli=1

Varley Masters report (as referenced by HBase documentation)
http://ianvarley.com/UT/MR/Varley_MastersReport_Full_2009-08-07.pdf

Big List of 20 common bottles necks

2012-05-29T13:46:00.001+08:00

All developers and implementors should take a look at this list of bottles necks from HighScalability.com

http://highscalability.com/blog/2012/5/16/big-list-of-20-common-bottlenecks.html.

Great stuff wish i have this list before i started work on any big systems.

Common Lisp the untold story

2012-05-15T10:05:00.000+08:00

Nice history about the Common Lisp standardization process by Kent Pitman who wrote the Common Lisp Hyperspec.

http://www.nhplace.com/kent/Papers/cl-untold-story.html

Opening Slides from Oracle vs Google

2012-05-02T09:37:00.001+08:00

The opening slides from Oracle
http://www.oracle.com/us/corporate/features/opening-slides-1592541.pdf

The opening slides from Google
http://www.groklaw.net/images/GoogleOpeningStatementSlides.pdf

It will be interesting to see how all this will come out, since it involves whether the API it self is copyrighted, not the implementation but the API signature itself, it the implmentation is the same then all the "worse" in Oracle's eyes.

Dr Dobbs has an interesting article @ http://www.drdobbs.com/jvm/232901227?itc=edit_stub talking about how all this has an impact on all programming languages and even OS's. Like JRuby is an implementation of Ruby and not forgetting the python implementations (CPython, Jython, IronPython).

Let's hope all this comes out in Google's favour though, i think it would be a major step backwards if no one can come up with a better implementation or an alternative implementation of the APIs.

Better Coding: Dealing with Exceptions

2012-04-06T11:31:00.001+08:00

During code reviews or debugging sessions, i always find new programmers having a hard time trying to deal with exceptions especially when the compiler forces you to do something with them. And the thing with exceptions is that if you don't handle them properly, you might have a hard time trying to debug your programs.

What are exceptions anyway?
Exceptions are conditions that change the normal flow of the program, they are usually in reponse to some part of the code having an unexpected error that the programmer needs to handle. Things like when you are reading a file you might get an IOException when something went wrong with IO operations, or when you are converting from a String to a number, you will get a NumberFormatException when the string is not a number.

So what are some wrong ways to handle them,

Don't just print the stacktrace.
IDE's tries to be helpful and will help you to automatically write the "try catch" block statements, and they will usually put in a e.printStackTrace() for you.

public void readAFile(){
    try{
        //Some code that tries to open and read a file
    }catch(IOException e){
        e.printStackTrace();
    }
}

What most people do after that is to forget about it. Printing out stacktraces usually is not advised, hackers can find out what your application does in the back end, and sometimes if you are not careful, SQL errors are printed out and the hackers can devise an attack based on SQL Injection.

Do Nothing!

public void readAFile(){
    try{
        //Some code that tries to open and read a file
    }catch(IOException e){
       //Do nothing;
    }
}

And then we are left scratching our heads what went wrong with the program because nothing was print out when there was an error! These are they type of errors that can make you stay up late in the office, because you simply can't see what went wrong from the UI, console or the logs.

So what should you do?

Rethrow the exception if the class can't handle it.

It is likely that your method might not be the best place to handle the exception, so you rethrow to the calling method to handle it.

Example: The FileLoader class tries to readAFile but things do go wrong when reading a file, but the FileLoader is probably not the best place to handle the error. The calling class and method would like to know when there is an error so that they can either do some remedy action, inform the user or log it. In this case SomeUIClass is trying to read the file and when FileLoader throws the exception, a messagebox comes out and logs the error to the log file.

  public class FileLoader{  
      public void readAFile(File f) throws IOException{  
           //file reading code  
      }  
 }  
 public class SomeUIClass{  
      public void readFile(File f){  
           try{  
                FileLoader.readAFile(f);  
           }catch(IOExecption e){  
                //Print some message to the UI to inform the UI that it failed to read a file  
                //Maybe log something to the log file  
           }  
      }  
 }  
>

Rethrow a more generic exception.

We all like to "program to an interface", but sometimes programming to an interface can be made challenging if we rethrow a checked exception. An example.

Let say we have an interface called BooksDao. It is an Data Access Object used to retrieve books. So we have an implementation called JDBCBookDao that retrive books that is stored in a relational database using SQL. So there is a chance that it will throw a SQLException when trying to retrive some data.

public interface BooksDao{  
      public List getBooks(String query);
 }  
 public class JDBCBooksDao implements BooksDao{  
      public List getBooks(String query){  
           try{  
                //Some JDBC code
           }catch(SQLException e){  

           }  
      }  
 }

But you see what happens if there is an error, it would be quite hard to tell the call method that an error has occured. But if we rethrow the SQLException like the previous rule then we are saying that all implementations of BooksDao.getBooks needs to throw an SQLException.

public interface BooksDao{  
      public List getBooks(String query) throws SQLException;
 }

What if we change the implementation of BooksDao to a MongoDBBooksDao ? and the MongoDB api dosen't throw an SQLException but throw a MongoDBException, we will be force to convert whatever exception that MongoDB has to an SQLException.

public class MongoDBBooksDao implments BooksDao{
 public List getBooks(String query)throws SQLException{
  try{
   //Some MongoDB api
  }catch(MondoDBException e){
   throw new SQLException(..);
  }
 }
}

The trick here is to create your own exceptions for your classes, this makes it easy to handle the different exceptions that the various underlying implementations can throw. All you need to do if just to re-throw the specific exception like SQLException to your custom exception.

public interface BooksDao{  
      public List getBooks(String query) throws DataException;
}  

 public class JDBCBooksDao implements BooksDao{  
      public List getBooks(String query) throws DataException{  
           try{  
                //Some JDBC code
           }catch(SQLException e){  
    throw new DataException(..);
           }  
      }  
 } 

public class MongoDBBooksDao implments BooksDao{
 public List getBooks(String query)throws DataException{
  try{
   //Some MongoDB api
  }catch(MondoDBException e){
   throw new DataException(..);
  }
 }
}

See it now looked much neater, what you should also consider is whether to re-throw all checked exceptions into unchecked exceptions. One limitation of Java is that if you throw a checked exception you need to declare it in the method, for unchecked you need not and it makes your interface cleaner because it does not need to depend on the exception. However you will need to make a conscious effort to try and catch the exception in your code. There are lots of debate on whether checked exceptions are better or not, i leave that up to you. My preference is that if you can throw an unchecked exception.

Hadoop World videos

2012-01-05T23:53:00.002+08:00

Hadoop World videos can be found here http://www.cloudera.com/resources/Hadoop+World/. Seems like I will be spending some time watching these for the next few weeks.

Links:
Hadoop project

Bing 2.0 API is useless

2011-12-29T22:03:00.000+08:00

Bing's 2.0 Search API is basically useless. The results dosen't match up with the Bing.com website and so testing is almost impossible.

And worse the results returned by the API are mostly irrelevant. I think Microsoft needs to seriously look at what are they targeting the Bing API for. Because as a developer i won't want to use it.

But there is a lack of freely available search apis out there.
Google Custom search requires you to search only specific websites that you specify and not google itself.
Yahoo BOSS requires payment so its out for me.

Anyone knows of what other options are out there?

Links to the issue:
Stack Overflow
Bing Community

Sheevaplug Debian Install

2011-12-14T12:02:00.000+08:00

Upgraded from the default Ubuntu install to Debian today, mainly followed the instruction by Martin Michlmayr. Mostly worked but the instructions for after installation of Debian to the MMC card was slightly different for mine.

These are the ones that worked for me.

setenv bootargs_console console=ttyS0,115200
setenv bootcmd_mmc 'mmcinit; ext2load mmc 0:1 0x00800000 /uImage; ext2load mmc 0:1 0x01100000 /uInitrd'
setenv bootcmd 'setenv bootargs $(bootargs_console); run bootcmd_mmc; bootm 0x00800000 0x01100000'
saveenv

The main difference is the mmcinit command, on my uboot it was "mmcinit" together, for the instructions that Martin gave was "mmc init" with a space.

Product Owner's Guide - Breaking down estimates

2011-07-25T16:58:00.004+08:00

Image: Ambro / FreeDigitalPhotos.net

Overhead this while at work.

"The Product Owner wants us to break down our inital estimate on the development effort into parts like analysis, design and coding ...".

That sounds to me like the Product Owner(PO) thinks that whatever estimate that the team came up with is too long and wants to cut the estimate. If the team gives such such a breakdown, then be prepared for the negotiation about the time needed for the project to be discussed.

But how is the team going to come up with such a figure anyway? I always found the statement like "Most of the time is spent in design but little in coding", or using the 80-20 rule that 80% is spent in design and 20% in coding. Is that statement still relavant today? In the past (I mean way way past), people do spent a lot of time in design because computers process ur programs in batches and you better get it right the first time if not you wait a day for the next run.

Fast forward to today, where we have powerful ides, programs run almost instantly, where you can code a little, test a little, you are more likely to try a program a vertical slice and then build up your system from there, with refactoring tools so powerful, changing methods, implementing interfaces no longer is such a chore.

Now back to the story, not matter what the project team tries to justify their number the PO will just try to cut it. The problem with most people is that they have some prenotion of when the project will end, but they do not realised that an estimate is just that, an estimate, it's a educated guess base on whatever information you have. An estimate is not an accurate prediction of the future and couple with the fact that software estimates are usually wrong. Steve McConnell says it well in his book Software Estimatation.

"Estimation should be treated as an unbiased, analytical process;
planning should be treated as a biased, goal-seeking process"

So if you ask someone for an estimate, you are asking for his opinion on how long it will take, and you shouldn't try to cut his estimate down.

More likely is the product owner is trying to get a plan from the team not an estimate, and the team's estimate isn't matching his plan. His plan can be anything, could be trying to meet some timeline for marketing, or some trade show demo.

Product Owners please just tell the team what is your plan, it may be because of marketing, budget and other reasons that you need to slim it down. But please tell the real reason and not by trying to get the estimate within your plan.

For the development team, try to find out the underlying reason for doing such an exercise, buy a copy of Steve McConnell Estimation book and give it to him. Negatiate on the scope, not all features need to be a mercedes, sometimes a vespa is good enough.

The only thing that can be reliably cut down to meet the target is actually the scope of the project. Does the Product Owner need 100% of all the features of the software to be done to be really useful? More likely than not something like 50-70% will probably be good enough.

Main takeaway - Estimation and Planning are 2 different things, try to make sure what is it you are talking about.

Expanding your toolbox - Picking a new language to learn.

2011-04-28T00:08:00.004+08:00

Image: graur razvan ionut / FreeDigitalPhotos.net

One day a developer on my team came up to me and asked, what should he programming language should he learn next to be marketable (and by the way he also thinks that Java is slowly dying).

Well as to whether Java is dying a not, I don't think so, a quick check with TIOBE shows that Java is still ranked among the top few languages and lots of places still runs Java. So i do have a job for the next few years.

But the thought came to me, it is worth learning things that are marketable or should you learn things that broaden your knowledge? What's your take on it? Should you expand your toolbox or have more of the same tools?

Steamhead takes the languages from Seven Languages in Seven weeks and puts it into a nice flow chart. I think all should go check that out and pick something out from that list. After doing quite a lot in Java I begin to appreciate the simplicity of using interpreted languages like python and php, and the fact that their frameworks are usually simple as compared to Java ones where sometimes we descend into XML configuration hell.

Steve Yegge has a interesting way of categorizing the various languages, he breaks them down into Nouns (Java, C# or OO languages), Verbs (LISP, Clojure or Functional Programming) and Verbs and Nouns (Scala, Ruby, Python, C++ or a Mixture of both).

Well for me I am more for the expand your toolbox model, go learn something that makes you have a new way of looking at things. A lot of people learn languages but they don't really learn design, think stuff like design patterns (Gang of Four, Java EE Design ...), SOLID principles, OO Metrics. Even if you know the syntax, you simply can't write maintainable programs and all you write lacks a certain craftsmanship to it.

By learning a different language and looking at the api, you can have a different idea about how to design your programs. An example will be like in Java. You have Math.abs a static function to get the absolute value of a number, have you ever wonder why its so "un OO" like? Compare with Ruby its just number.abs(), simple and elegant and fits into the OO paradigm.

In short

If you know Java, C# go learn Lisp Dialects (Common Lisp, Clojure), Haskell, Ruby, Python...

If you know Python, Ruby, you are pretty much there, since you straddle the limits between the 2 kingdoms.

If you know Common Lisp, Clojure, dont bother learning any other thing since you will think why in the world Java, C# programmers are typing so much code and configuring so much XML.

If in doubt just learn PHP to be marketable :)

Amazon.com Widgets

One hour early a day...

2011-02-02T11:14:00.001+08:00

My latest read is Robin Sharma's book (The Leader who had no title), interesting read. But one statement struck me (I more or less paraphrase it)

"If you wake up one hour early each day for a month, in 30 days you will have almost one weeks worth of working time, think of the things you could do"

When i told this to some of my colleagues/friends they say wha sleep less one hour how ? Not enough time to sleep already.

"You have enough time to sleep when you are dead"

I guess this is the difference between people who do impressive/great things (physically fit, be it in doing voluntary work, open source projects, making lots of money, hobbies, making a difference, side business, execise often) and the rest of us. They spent the time not just dreaming and talking about it but actually doing it. I am not actually saying that you forgo sleep altogether but think of the possibilities that could happen if you think about how to spend your time wisely.

At the end of our life, lets not spend time regretting what it might have been, or what we might have done better.

Remember the saying that you need 10,000 hours to become good at what u do, maybe i should start doing things instead of writing things on my blog :)

Ebooks from top StackOverflow answers

2011-01-26T23:37:00.002+08:00

Have you tried StackOverflow, if you are a developer its probably one of the best resource for asking questions.

Its a great site, what is even greater is that someone converted the best answers into an Ebook format.

Great for bring around, the link is here http://hewgill.com/~greg/stackoverflow/ebooks/. Whats nice is that it is broken up nicely into the different subject like ajax, python, c#.

Posting data with Node.js

2011-01-25T17:53:00.001+08:00

Recently i needed to post data using node.js, I was not trying to post a long string of data but rather parameters from a form. But the Node.js help page isn't too helpful, it just say use request.write() to write data to the stream

This is the first interation i got.

var http=require('http'); var post=http.createClient(80,'localhost'); var request=post.request('POST',/test.php'.{'host':'localhost'}); request.write('test=10'); request.end(); request.on('response',function(response){ response.setEncoding('utf8'); reponse.on('data',function(chunk){ console.log(chunk); } });

test.php is a simple php script that prints out the parameter value.

I got nothing... nothing was printed out. What was wrong?

Using curl and Fiddler, i did a little investigating about what went wrong, what was missing was the Content-Length and the Content-Type which needs to be application/x-www-form-urlencoded.

Adding these 2 parameters to the script

var http=require('http'); var post=http.createClient(80,'localhost'); var request=post.request('POST',/test.php'.{'host':'localhost','Content-Length':'7','Content-Type':'application/x-www-form-urlencoded'}); request.write('test=10'); request.end(); request.on('response',function(response){ response.setEncoding('utf8'); reponse.on('data',function(chunk){ console.log(chunk); } });

And yeah ! It works !

JRex, Embedding Gecko (Firefox) in eclipse

2011-01-11T17:29:00.001+08:00

Jrex is a Java component that embeds Mozila Gecko in your application. The project has been dead for some time since 2008 from what the mozdev.org page. So the version of Gecko may not be the latest but should be good enough for whatever you would like to try out.

However looking at the code from Vijay (http://www.vijaykiran.com/2006/09/05/using-jrex-in-eclipse-rcp/
), i got it working and it seems to work fine, but Vijay dosen't really go into how to setup the project like where to download the jars and where to put the dll and so on, and I did have some hard time trying to find out where to find the jars.

Downloads
1. At first i took apart the jnlp file on jrex.mozdev.org to find out what are the dependencies, but after looking around the mozdev site, i finally found the downloads for the jars, source and docs in here (http://www.mozdev.org/source/browse/jrex/downloads/#dirlist).

2. But it dosen't include the jrex_gre files that are in the jnlp, those you can get them here (http://www.mozdev.org/source/browse/jrex/www/releases/jrex-1.0b1_dom3/). Look for the jrex_gre.jar

Setting up your eclipse.
Put the jrex.dll in your eclipse directory, if not you will get a UnsatisfiedLinkError when you try to run the view. Put the jrex.jar in your lib folder of your project.

Unzip the jrex_gre.jar contents to a nice location you can remember. You will see in Vijay's code a place that you will need to supply the path to the file in org/mozilla/jrex/jrex_gre files.

That should fill up the missing pieces in Vijay's writeup.

I will try to package the source code into github at some later time.
&n bsp;

Fedora 14 - Using the DVD as a software repository

2011-01-06T09:32:00.001+08:00

Installed Fedora today at office in order to try out some web acceleration stuff lile squid and varnish. I used the DVD iso version, so that i can have most of the essential software already.

When i rebooted i found that the dvd is not recongnised as a software repository, because there is no entry in /etc/yum.repos.d/.

No biggie, just mount the dvd, in the root of the dvd there is a file media.repo, jus copy the file to /etc/yum.repos.d/ as packagekit-media.repo and you are all set, your dvd becomes a software repository.

Resolutions 2011

2011-01-05T09:53:00.001+08:00

My resolutions for 2011.

For the personal geek in me (Probably have little to do with work)

I declare this to be the year of functional programming for me!

Common Lisp

Begin by first completing Practical Common Lisp and Land of Lisp, and the little pet project that i do when i have free time, the idea of closures and high order functions really appeal to me.

Erlang

Another Functional Language that I hopefully have time for this year. Invented by Ericsson for using in telephony applications, it has some interesting properties like fault tolerant and hot swapping. Since it's designed for telephony (which has something like 9 9's of availability) you can actually swap in code while the system is running which i think its pretty cool.

Hadoop/Map Reduce

Always heard about MapReduce and Hadoop, I shall attempt to read google's paper on it and hopefully setup a working instance.

NoSQL

NoSQL is getting big nowadays with Twitter and Facebook all moving/developing part of their infrastructure on top of NoSQL type of storage.

Learn at least one implementation and see how it can be worked into a project.

For the bookworm in me

Read The Elements of Style, one of the great books on the writing for the English language. Time to get better at my writing, better written communication is essential as you go along ur working life.

Read more "management" style books especially in the realm of making people happy at work, I am quite interested in how great organizations retain their people and keep them happy.
So far i have FISH! tales, Why work sucks from the library here with me.

For the not so fit me

Finish taking my IPPT before June and pass it.

Run at least once a week at least 2.4km.

Attempt to run a half marathon by then end of the year. (Haha this will the hardest one in my list)

For the bad habits in me

Second guessing or interrupting people midway

I don't know if people noticed but i do have a bad habit of either completing other people's sentence or second guessing what they will say. I will let others finish what they want to say before I start, I will try to follow the rule of One Conversation at a time.

Procrastination

I have a habit of procrastinating, enuff said.

For the father and husband in me
Vacation

Hopefully I will have time to go for a vacation, hopefully it will be the first time that I am bringing Chloe overseas.

Better Father/husband

Its quite hard trying to be specific as to what makes a better father, could be a variety of factors but i sorta like this one that I got from FISH! Tales book, "Love for child. is simply being there".

Lets look back again in 2012.

Reflections on 2010

2010-12-28T21:07:00.001+08:00

Well 2010 has come and soon will be gone, so time to look back.

I have been married for 2 years now although there are ups and downs but I am happy that I have a nice wife and a cute (and she continues to amaze me everyday) daughter.

Being a father does entail some sacrifices, no longer will you have "your" time, but rather it will be the "family's" time or more accurately the "baby's" time. But the smile of Chloe when she see you wake up and when she is scared and runs to hugs you ( only when the mum in law not around) makes it all worth while. But as for having another one .... lets wait and see :)

Hdb finally decides to give me my house, and it is in the process of renovating, left the painting and the carpentry to be done and it should be ready to move in.

Work wise has been good, finally saw a project from the start to the OSAT phase, couldn't see it all the way to the end though, got rope into another project, as a Software Develop ment Manager, its sort of like a Project Lead kinda thing. Challenging though because the project had already been running for sometime before I came in and there are lots of stuff that I need to pick up and be very familiar with. I am aware of the Peter Principle and the Dilbert Principle, hope that this is not the end yet :)

On more personal note, I have been trying to pick up the Diatonic Harmonica, practicing while waiting for my wife to go off work. Always sort of regretted that I never did pick up a musical instr ument, haha now trying to catch up. Seems like a lot of people around my age are playing catch up in music, I know a few who are trying to pick up the piano, trumpet and the violin.

Hope to play like this guy below someday!

or even this guy!

Till the next time...

Winston W Royce - Father of waterfall

2010-11-26T21:53:00.001+08:00

Uncle Bob posted an article, What killed waterfall could kill agile.http://cleancoder.posterous.com/what-killed-waterfall-could-kill-agile. He mentioned about a person named Dr Winston W Royce (whom uncle bob called the "Father of waterfall") who published a paper, Managing the Development of Large Software Systems: Concepts and Techniques, in which a system of developement now know as the Waterfall model was described.

What shocked me in that paper was not that he advocate the waterfall model, but rather he condemns it. In his own words
"I believe in this concept, but the implementation described above is risky and invites failure".

The funny thing is so many generations of programmers who studied in colleges and university were brought up believing that it was one of (or depending on how old you are) or "the" model of how software actually gets built. Now we know better, that's why we have things like the Agile movement, Kanban and so on

If you read the paper, you will discover he has views on how to improve the process and what is surprising is how similar it is to practices that we are advocating today.

His 4th and 5th recommendation looked remarkably like Agile practices.

Step 4: Plan, Control and Monitor Testing
Testing

Code inspection
He advocates the use of code inspection by a second party, he said the use of computers would be too expensive for this task. But with the computing power we have today. Software like Findbugs or JTest can help in the first line of bad code detection and Pair Programming helps in that aspect too.

Code Coverage
Code coverage is also advocated in fact he advocates testing every logical path if possible and if he is the customer he would not accept delivery until this step is done. Although he acknowledges the difficulty in accomplishing this step for large programs.

Step 5: Involve the customer
He knows that software design and specifications is open to a wide interpretation even after agreements, customer involvement in his words should be "formal, in-depth and continuing".

Let's not remember Winston W Royce as "Father of the waterfall" but rather one who saw how software development could be done better 40 years ago.

Relational selects in YII

2010-11-20T08:27:00.001+08:00

How do you do relational selects in YII? The kind where you have a many to many relationship on a table. The YII page on relational queries didn't have many good examples on how to do it, so I tried it out and found it to be actually quite easy, its quite like how you would do for single table query.

The above figure was taken from the YII page on relational queries (I was too lazy to do up my own example).

We will just concentrate on the tbl_post , tbl_post_category and the tbl_category tables.

I will assume you know how to overwrite the relations function in CActiveRecord to setup the relations correctly.

So the scenario is, I would like to retrieve posts that are in a certain category.

The idea is to use the with() method that is part of CActiveRecord, we would like to retrieve the categories together with the Posts.

So the query would look like this:

$posts=Post::model()->with(array('categories'=>array('condition'=>'name="FunStuff"')))->findAll();

In the with portion you specify the relations that you want to load in this case categories, and with it you can specify the different relation query options like select, condition and so on. In this case we use the "condition" option to specify what from categories that we want to retrieve. For this we want to retrieve all the Post with categories name = "FunStuff".

Simple rite!

LOTW - 11 Oct 2010

2010-10-11T21:09:00.001+08:00

Design Principles Behind Smalltalk - One of the most influential language although it didn't become popular. Java, Ruby all draw inspiration from it. If you are a programmer you owe it to yourself to go try Smalltalk. Squeak and Pharos are probably the more famous of the free implementation around.

Google's answers to Oracle's allegations

Doing quite a bit of PHP programming these days so there are the few links that might be useful
Using Emacs to edit php files
Geben + XDebug to debug php code on emacs - Haven tried this, so far with PHP, doing print statements still works for me.

AptOnCD Backs up all the packages that you have installed, making it easy to restore your packages instead of downloading them all again.

LOTW - 4 Oct 2010

2010-10-04T11:24:00.000+08:00

A really simple introduction to Map Reduce - Great intro to what Mappers, Groupers and Reducers are all about. I was scratching my head about Map Reduce before this came about.

How big are Facebook's data centers? This FAQ will tell you all that you need to know including servers, software, location and expansion plans.

Google URL shortener goo.gl opens for business

Heard of the Arduino, unknown to me there is actually a Netdunio yeap, and it runs on .Net. Scott Hanselman talks about it.