Max Völkel

Every click counts

2009-11-11T21:31:00.003+01:00

A shot post on usability. Something that must be said. In user interfaces, every click counts.
That means, whenever I ever clicked on anything, the application must try everything to apply the semantics of this click forever.
The application must exploit and persist every decision a user has made -- until she expresses the contrary.
There should never be the need to run the same sequence of user interface commands again and again.

Practically, if I do spell-checking, the UI could remember my choice and apply the same spell-checking again, when I re-run spell-checking. Or even better: Highlight my choice so that I can press just enter. Or ask me, if this choice should be applied forever.

Loss of relevance for personal notes

2009-10-28T18:39:00.002+01:00

From summer 2008 to Autumn 2009, 55 people have been interviewed with an online questionnaire the following questions (among others):

A) In one week, how many personal items do you write down?
B) Of these personal notes, how many are still relevant (in percent)
- ... after one day?
- ... after one week?
- ... after one month?
- ... after one year?

The average values for (B) are 71,55%, 51,73%, 36,09%, 20,55% with rather high standard deviations (0,223, 0,265, 0,278, 0,243).
However, when computing the loss of relevance from one time point to another one we get:

Loss of relevance on first day: 28,45% (0,223)
In the next six days: 19,82% (0,161)
In the next three weeks: 15,64% (0,139)
In the next 11 months: 15,55% (0,146)

with somewhat nicer standard deviations (in parentheses). Interpolating this we get the fraction of relevant knowledge after n days as depicted in this chart:

Assuming one creates 10 new personal notes every day, then the personal notes collection contains after 100 days 1000 notes of which 389 (38,9%) are relevant. After 500 days, 1368 of 5000 notes (27%) are relevant.

From Documents to Knowledge Models

2009-09-24T12:53:00.001+02:00

Aha, mal wieder ein Beitrag in Richtung "From Documents to Knowledge Models".

Knobelaufgabe

2009-09-23T14:03:00.004+02:00

Beim Schreiben seiner Doktorarbeit muss max knobeln.
Er hat 10 Frage-Päarchen mit je zwei Fragen (a) und (b).
Er hat fünf Probanden.
Nun muss er jeden Probanden befragen, so dass

Er von jedem Fragepäärchen mindestens 2 x (a) und 2 x (b) verwendet hat. Dabei is es unvermeidlich das er pro Frage einmal mehr (a) oder (b) verwendet. Insgesamt sollen weder (a) noch (b) bevorzugt werden.
Jeder Proband soll je fünf (a)-Fragen und fünf (b)-Fragen beantworten.
Wenn er Proband 1 und 2 mit (a) befragt, also Proband 3,4, und 5 mit (b), dann soll es keine weitere Fragerunde geben, in der Proband 1 und 2 den selben Buchstaben bekommen und 3,4 und 5 andere. Ander gesagt, die Aufteilung von Probanden in zwei Grüppchen soll für jede Frage anders sein.

Wie muss Max die Probanden befragen? Gib für jeden Proband an, was er gefragt wird (a,b,a,a,...).

Wieviele Lösungen gibt es?

Einige Antworten werden in Kapitel 6 der Doktorarbeit veröffentlicht.

Das braucht die Welt

2009-08-02T14:28:00.001+02:00

Simpel und nützlich.

Detect Unnecessary Code

2009-06-18T15:01:00.004+02:00

A nice little Eclipse plugin that finds all methods and variables that are public -- but not used anywhere in your workspace!

Furthermore, it finds all methods that could be marked private or protected without harming the project.

Both makes your code easier to maintain! Try it.

Wave

2009-05-29T09:41:00.002+02:00

Hi, I can not clearly tell you why, but I am pretty sure that Google Wave will become a really important player in the Web 2.0 / collaboration market.

They plan to open-source the whole thing -> This gives developers confidence
They will host the server as well -> This lets developers start easily
They thought about merging asynchronous + synchronous communication
They have the notion of robots to automate behaviour

Denkwerkzeug SPAM

2009-05-15T18:40:00.002+02:00

My Google alert for "denkwerkzeug" brought up a strange URL.

I received this snippet by email:

=== Google Web Alert for: denkwerkzeug ===

Degauss Coil
Ich will ein denkwerkzeug, imitrex dosage dass mir verschiedene sichten auf
das selbe set von w rtern oder textschnipseln erlaubt diese verschiedenen
...
http://mebil.agilityhoster.com/cheap-lo24/cheyom.html
Note: I tweaked this link-text to point to http://www.stopspam.org/.

This once a day Google Alert is brought to you by Google...

When clicking on the link you get immediately redirected to another crappy page with a big red button labelled "don't click". I didn't click.

Then I got curious and googled and found this:

http://www.25uhr.de/wordpress/?p=181

That is where the spammer spidered the text from. Including the Umlaut-bug.

The spammers website looks like this:

(tons and tons of CSS delcarations)

<div id="side-col">    <ul id="services">       <li id="logo-design">Friendly Sites<br>           <li class="selected"><li class="selected"><a href="ctrasstheda.html">car nascar setupa>li><li><a href="uretexich.html">buy chevy enginesa>li>li>li>       <li id="web-design">Other Pages<br>           <li class="selected">li>li>

      <li id="valid-markup">Menu<br>           <a href='index.html'>Degauss Coila> :: li>           ul>     <h3> h3> div>  <div id="main-content">

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  <p id="footer">       Copyright Â© 2008 by Degauss Coilp> div>  body> html>

Is there something fun an clever we can do against them?

Symptom: java.lang.IllegalStateException: Level number 20 is not recognized.

2009-05-14T04:01:00.001+02:00

Problem: Somebody logs to an slf4j version 1.3.x

Solution: Replace slf4j 1.3.x with slf4j 1.5.x

Latex Tips

2009-04-30T21:01:00.002+02:00

Two great packages! This post is dedicated to Jens :-)

placeins
Just put
\usepackage{placeins}
at the beginning an then
\FloatBarrier
wherever floats should not float across. This really tames flots nicely! E.g. if a float should be placed before that other subsection is startet: Just put ub a float barrier, and it will not come later.

zref
This is aresome! It enhances labels with the ability to carry arbitrary metadata. I used it in my PhD for consistent requirements numbering. It works like this:

\usepackage[user,titleref,hyperref]{zref}

\newcounter{requirementcounter}%
% === requirement definition
\newcommand{\requirement}[3]{%
\refstepcounter{requirementcounter}%
\ztitlerefsetup{title=#3}%
\zlabel{#2}%
\paragraph{Requirement \therequirementcounter: #1}%
\hypertarget{#2}{}
}%
% === requirement reference
\newcommand{\reqref}[1]{%
\hyperlink{#1}{\zref{#1}}~$^{\textrm{\ztitleref{#1}}}$%
}
% === requirement reference by number
\newcommand{\reqrefno}[1]{%
\zref{#1}%
}

I used these definitions like this (6 other \requirement defs come before):
\requirement{Simultaneous use of Different Levels of Formality}%
{req:simultan}{simultaneous formality levels}
Often research notes and references are already managed digitally. Works in PIM \cite{PIM2006Proc} and Semantic Desktop research have further stressed the need for unified search and organisation of a user's personal items.

This defines three parts for the requirement: A long name, a shorter title and a keyword-like name. The macro further assigns a unique number in order of appearance.
This example renders as
Requirement 7: Simultaneous use of Dierent Levels of Formality Often
research notes and references are already managed digitally. Works in PIM Proceedings
of the Second SIGIR Workshop on Personal Information Management
(PIM) (2006) and Semantic Desktop research have further stressed the need for
unied search and organisation of a user's personal items.

A reference like
\reqref{req:simultan}
is then rendered as
7^{simultaneous formality levels}

Zref seems to be able to do much more, so read the doku!

Thomas Pogge verändert die Welt?

2009-04-30T16:01:00.003+02:00

In der letzten Ausgabe der ZEIT war ein schöner Artikel über Thomas Pogge, der gegen die Armut in der Welt anschreibt - und angeht!
Die Leserkommentare der Online-Ausgabe verirren sich ruck-zuck in Überbevölkerung, Islam, und Korruption. Ja, wie wird man Korruption los? Keiner den ich fragte hatte eine Idee.

Can Adsense in Gmail help spammers?

2009-04-27T11:56:00.003+02:00

Just a little insight. If a spammer manages to send spam to my GMail account - which is not so easy, but does occur almost every day - then I get ads beign displayed on the right, matched to the content. GMail does not load images, I do not click links, so the spammer cannot know, if I ever read the email. However, by butting bogus words such as LKJAKFJHWK in the mail and buying adwords for just that word, he could get advertisements shown next to the email. If he would buy a "pay-per-view", he could get to know when I watch the mail. Maybe this just allows the spammer to find out how well he got arounds GMails spam-protection.

SKOS is great!

2009-04-11T15:50:00.001+02:00

They fix so many bugs from OWL, e.g. the owl:sameAs is so useless for PKM, skos:exactMatch is much cooler. Sec. 3.6 of my thesis in progress is happy, too.

How to become a good developer

2009-04-06T14:46:00.002+02:00

Some of the students I work with asked me: How do I become a good (Java) developer? Instead of an answer, here is a reading list, that will hopefully help.

Read good books

The Pragmatic Programmer: From Journeyman to Master (Paperback)

Design Patterns

Wikipedia on THE book - examples in smalltalk and C++
Java Design Patterns - Free ebook (PDF) from 1998

Listen to good podcasts

Review of Software Engineering Radio (se-radio.net) Podcasts for new developers
The ratings are highly subjective and indicate my personl recommendation of relevance for junior developers as well as sound quality etc.

#81: 4 stars - Nice motivating episode with Erich Gamma (Patterns, JUnit)
Interview Erich Gamma
#82: 4 stars - Organisation of large codebases into modules, packages, classes etc is a very important aspect of SE to keep complexity mangeable. Evolution of APIs!
Organization of Large Code Bases with Juergen Hoeller
#83: 4 stars - Requirement-driven SE with a very nice British accent
Jeff DeLuca on Feature Driven Development
#94: 3 stars - Introduction to business models with open source. Explains different motivations for organisations to do open-source and different ways to make money
Open Source Business Models with Dirk Riehle
#98: 4 stars - Every developer should know REST - nice introduction
Stefan Tilkov on REST
#104: 2,5 stars - Good intro what a plugin really is.
Plugin Architectures
#109: 4,5 stars - Enlighting episode how to deal with a very complex, scalable, evolving IT system
eBay's Architecture Principles with Randy Shoup
#110: 4,5 stars - Basic knowledge about different roles in SE!
Roles in Software Engineering I
#112: 4,5 stars - Second episode
Roles in Software Engineering II
#114: 4,5 stars - Requirements engineering is hard, the episode is well-structured
Christof Ebert on Requirements Engineering
#117: 4 stars - Good intro from behind the scenes what UML is and isn't
Bran Selic on UML
#118: 4,5 stars - Solid demystification of a basic technology
Eelco Visser on Parsers
#119: 4 stats - Inspiring introduction to an emerging technology
DSLs in Practice with JP Tolvanen
#123: 3,5 stars - Good overview to model-driven anything
Microsoft OSLO with Don Box and Doug Purdy
Unreviewed episodes: #0 - #67, #69 - #71, #73 - #79, #85 - #86, #89, #91 - #92, #95, #125, #127 and newer.
Episodes not mentioned have less than 2,5 stars.

Suggested order:

Start with Roles in SE (#110 and #112), then learn who defines what will be built: Requirements: (#83).
Next learn about quality via patterns and testing (#81), learn how to deal with API changes (#82). Round up your knowledge with two nice episodes on loose coupling basics (#98) and applied (#109).
Then listen to individual technologies like parsers, UML, DSLs and modeling.

Ok, enjoy listening and give me and other readers some feedback - e.g. if you more introductionary material to become a good developer.

Web Programming

2009-03-23T15:48:00.002+01:00

(Originally written on 21. Februar 2009)

Listening to an episode on SE-Radio on Haskell made me think. Haskell is a pure functional programming language, in the sense that all functions are side-effect free. This makes debugging and testing much easier. From another perspective every function in Haskell is a well-defined interface between two components.

On the web, one main feature of the REST-style architecture is the side-effect free GET-method, which makes caching by intermediaries possible, which in turn makes the web so fast. Datatypes on the web are MIME content-types. So instead of calling a function with an getting a return type, on the web you call a function and express a list of desired return types in ascending order. Compared to programming languages, the type system of the web is rather weak. E.g. the IANA which is responsible for maintaining the registry of content types lists less than thousand types. Of course, many vendor-specific types are not listed there. Web APIs emerged together with the Web 2.0 hype. These APIs are described in natural language terms. In principle, the web has both call-by-value (sending data, returning data) as well as call-by-reference (sending URI, returning data).

The semantic web an RDF could serve well to describe a rich type-system. The missing building block for treating HTTP GET calls to URLs a functions in a programming language is a sort of language and compiler or runtime environment, that allows to compose functions etc. Or a library could map function calls in Java automatically to HTTP GET calls.

Hmm, this post seems unfinished. I'll post it anyway.

How to learn CSS

2009-03-12T15:28:00.003+01:00

CSS ist the back-bone of web-applications. It's a wonderful declarative language. You should learn it, here is how:

Visit Zen Garden to see how beautiful CSS can be.
Use Firefox and get Firebug from http://getfirebug.com/
Visit any website and open Firebug by clicking F12.
Learn how to inspect and tweak CSS of any website
Print the CSS CheatSheet 2-page PDF summary and put it next to your PC.
Forget all tutorials, web schools and whatever.
Rely only on http://www.w3.org/TR/CSS2/ and read it.
Learn the basic formatting models (normal, floating, ...)

Take home messages:

CSS is much like LaTeX, both were designed to render text and figures
With CSS2, you can change the semantics of ANY HTML element. Yes, you can e.g. make headlines look like bullet list items or the other way round. Your fantasy is the limit.
CSS purists don't like tables. However, many things work only with tables. Do use tables. But use few of them and only if you need them (if you don't get things done with CSS in 5 minutes).
Learn CSS by inspecting other cool websites with Firebug. There are e.g. ca. 10 different ways to create "rounded corners" and they are all somehow "primitive". But they work.
Test CSS on different browsers, but ignore Internet Explorer 6, that one is just broken.
Firebug is your CSS editor. Explore it well an learn e.g. to move values with the up/down cursor keys to perfection while the live website changes.

Tools:

Free CSS Editor Plugin for Eclipse - syntax highlighting, autocomplete, outline.
Use it only to not loose overview when you edit a lot in Firebug. Copy and paste the changed CSS from Firebug to Eclipse and use the auto-format source to make it readable. Comment your CSS well. Firebug kills all formatting and all comments, so copy-and-paste only small portions.

Solvr

2009-02-24T09:06:00.002+01:00

I just found a nice little tool in the spirit of Meet-o-matic (great for making appointments).
Solvr is a tool that helps you to think structured about a problem. No logins or stuff required, just like in Meetomatic. But be careful: At Solvr you really need to set a bookmark, I won't send you emails.

Programming Insights 3 - Make errors localisable by design

2009-02-15T21:58:00.003+01:00

Errors may not be a huge problem is they cause not much harm (e. g. if they occur in a CMS for a web shopw) and if they are easy to fix. Most errors are easy to fix if the are localisable within a component. And if that component is rather small. Therefore one should design module systems where at the component boundaries there are strict checks. This makes errors localisable and easy to fix. So it is at development time less important to avoid them, so it is possible to develop much quicker. To achieve strict checks at component boundaries, the "surface" where two components touch should be small. So interfaces between components should have simple data structures and few methods. Taken to the extreme, each component has simply one method: "process this change object".

2009-02-10T10:42:00.002+01:00

I just read the German book Die Kunst, vernetzt zu denken: Ideen und Werkzeuge für einen neuen Umgang mit Komplexität from Frederic Vester (1925-2003).

And I must say: I am impressed. Thus guy was really cool. He saw that many people discuss problems only in small parts and never see the big picture. He did not got research funding. So he went on and created a company and developed the model and tools to let his vision happen. At the end he has an impressive list of ca. 50 published studies based on his models and tools.

PKM2009 is third-largest workshop

2009-02-03T18:49:00.002+01:00

PKM2009 is with 35 registered participants already third-largest workshop at the
5th Conference Professional Knowledge Management. Register now before we run out of space!

Memory Consumption of Processes in Windows XP

2009-02-02T10:08:00.003+01:00

Just a small note to myself: The memory usage displayed in the task manager does not match the total memory usage displayed in the graph. When you terminate a program using x MB RAM, you will free 3x RAM in the graph display. Estimating memory footprint of software should thus better be done using the graph display.

Programming Insights 2

2009-01-28T20:10:00.002+01:00

Having Richard in my comments reminds of another great quote:

"You can either solve a problem - or make it a configuration option"

- Richard Cyganiak

Richard, I love this quote and keep telling it my students and colleagues when they get dreamy eyes and say proudly: "wow - we can simply put it in the configuration file ... to let the user decide which filter to use instead of a default filter when the default defaultFilter could not be loaded " - or similar things :-)

Programming Insights 1

2009-01-26T13:02:00.002+01:00

In API design, strive for clarity over convenience. Convenience often leads to confusion, confusion is chaos, chaos is not convenient.

Clarity of an API must be the overall goal.

Instead of
interface A extends B{
...
}
to make it convenient to use A's as B's, better add a method
interface A {
B asB();
...
}

Google Desktop Search + BibTex?

2009-01-21T16:59:00.002+01:00

I searched all the known web, but there is no BibTex index plugin for Google Desktop Search.

Second, I just wonder: With all the indexers out there (bundled with Lucene, Strigi, Aperture, GDS, ...) when will we see an abstraction framework for them? Possible a simple web service that returns for a URL such as localhost:1234\indexer\file=C:\mydir\myfile.ext an XML response with extracted metadata and textual content. This way one could separate the value creation on file format understanding from the value of efficiently indexing stuff. Maybe the user interface is then a major thir part. Today, all three parts (translating whatever to text, indexing text, UI) are always bundled. As a result, all desktop search engines still suck.

Counting Lines of Code in Java

2008-12-12T22:32:00.002+01:00

I searched half an hour, installed the famous metrics-plugin from sourceforge, could get it to run on some projects, but not on others. Played around, no luck. Searched for another half hour. No luck. Either you use the metrics plugin or you can your lines of source code yourself. In another half hour I wrote a simple Java program to count the lines of code, including comments. But hey, it even ignores blank lines. I was most surprised that coding was actually faster than searching.

Here is the complete code:

package de.xam.loc;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public final class LOC {

public static void main(String[] args) throws IOException {
if (args.length == 0) {
System.out.println("Usage: LOC ");
} else {
LOC loc = new LOC();
File root = new File(args[0]);
loc.countLinesOfCodeInDirectory(root);
System.out.println("Found " + loc.lines + " lines in " + loc.files
+ " files within " + root.getAbsolutePath());
}
}

private long files = 0;
private long lines = 0;

private void countLinesOfCodeInDirectory(File dir) throws IOException {
for (File f : dir.listFiles()) {
if (f.isDirectory()) {
countLinesOfCodeInDirectory(f);
} else {
if (f.getName().endsWith(".java")) {
BufferedReader br = new BufferedReader(new FileReader(f));
String line = br.readLine();
while (line != null) {
if (!line.trim().equals("")) {
this.lines++;
}
line = br.readLine();
}
br.close();
this.files++;
}
}
}
}
}

Maybe one day this will end up in an Eclipse or Maven plugin ;-)