bodom_lx at task3 dot cc

My first day at FBK has just finished, so there are some updates. I’ve uploaded about every document to the Wiki regarding my analysis of the papers. The Analysis Grid is available for view and as a PDF file. Chek them out at http://www.opensocialcapital.com/dynamic_carpooling/wiki/!
For the next week I’m going to review some existing mobile application. I will also contact some Opentrip members to ask them about the status of their work. I will contact the author of dynamicridesharing.org Wiki to ask him some information.

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While I am waiting for my wiki to be setup, I’m updating here my first week of work. I read lots of papers regarding dynamic car pooling and friends. Most of them are listed on this MIT website and on dynamicridesharing.org. The second site is maintained by Dan Kirshner, the author of three (unlucky) experiments regarding dynamic car pooling.
I actually selected 13 publications for my scope. I’m going to publish the list as soon as I’ve got my wiki. What I’m going to do is to review them, comparing my work with the excellent one done by Hannes Zimmerman and Yann Stempfel (Current Trends in Dynamic Ridesharing, identification of Bottleneck Problems and Propositions of Solutions).

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I’ve just started an internship for my University. I’m working at the Fondazione Bruno Kessler, a research organization of the Autonomous Province of Trento that promotes research in the areas of science, technology, and humanities. In particular, I’m at the Center for Information Technology – Irst, in the SoNET explorative unit.
My research activity will last until the end of January and hopefully continue during the second semester, if the collaboration will be fruitful enough for a thesis.
The internship activities will focus on Dynamic Carpooling. I’m going to use my blog and the new category /carpooling-research to publish updates about the status of my research. We are going to purchase a domain that will also contain the outcomes of the research activities, available to the general public.
Here is a quick overview of the contents of my internship:

1. Dynamic Ridesharing Reviews

• Review of existing papers
• Review of existing web and mobile applications
• Review of protocols
• Research about the motivations of failure/success of existing realities

2. Release of Prototypes

• API definition for Dynamic Carpooling
• Implementation of a web application for Dynamic Carpooling
• Implementation of a mobile application for Dynamic Carpooling
• Possible integration with FBK systems

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BD-review is a dynamic website to allow people to review releases (albums, demos, EPs, singles) of (young, unsigned) music bands. The project is the outcome of the Internet Technologies course at the Faculty of Computer Science of the Free University of Bolzano. The requirements of the project were to build a website using a small subset of JavaEE technologies, without the use of web-frameworks.

A screenshot of a Review

The project is not really meant for production use. It was made as a strong, working and correct base for studying JavaEE academically. It should be useful for every student (also non-student) willing to have an overview on JSP and study it. The code is well-written, uses MVC, and the whole project is documented in detail in a 20+ pages report.

Read more on the project page, download the sources and play with it! Please let me know about your experience with BD-review code.

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BD-review is a dynamic website to allow people to review releases (albums, demos, EPs, singles) of (young, unsigned) music bands. The project is the outcome of the Internet Technologies course at the Faculty of Computer Science of the Free University of Bolzano.  The requirements of the project were to build a website using a small subset of JavaEE technologies, without the use of web-frameworks.

Therefore, this project is not really meant for production use. It was made as a strong, working and correct base for studying JavaEE academically. It should be useful for every student (also non-student) willing to have an overview on JSP and study it. The code is well-written, uses MVC, and the whole project is documented in detail in a 20+ pages report.

A screenshot of a Review

I encourage to read the PDF report of the project. It contains detailed information about the analysis and design phases, as well as the architecture description, screenshots, problems found etc. Please read also the README file. It contains configuration instructions.

There is a running demo located on the evaluation server of the course, but I think it will be removed soon.

Quick Jump:

Vision

Requirements Implemented

Technologies Overview

Download

License

Vision

The aim of the project is to build a dynamic website to allow people to review releases (albums, demos, EPs, singles) of (young, unsigned) music bands. Users will be able to signal interesting materials and review them, while other users will be able to comment the reviews, too.
This web 2.0-oriented application should allow unknown talented musicians to achieve a higher notoriety but also to improve their productions.

Screenshot of the personal user page

Requirements Implemented

I report here the requirements of the course, all implemented by BD-review:
What BD-review implements is:

• User Management
  • List existing users of the system
  • Creation of a new user
  • Deletion of the existing user
• List and modify access rights of the users
  • check boxes with some capabilities (min 3)
• User registration and login to the system
• Items management
  • Users add, edit or remove items
  • Users comments or reviews items
  • Administrator can manage the comments (edit,remove, add)
• Personalization
  • Salutation for a returning user
  • List resources that are new from the last visit
  • Customization of the layout for a class of users.
• Techniques – MUST be used
  • Static HTML
  • CSS: all the look and feel must be in CSS files
  • Javascript: check input and manage menus
  • Servlet: Reading (parameters and headers) and writing headers and resulting page
  • Servlet: Session management with cookies and session object
  • Servlet: Redirect the client
  • Servlet: Forward to another page or servlet
  • JSP: Expressions, scriptlets and declarations Beans
  • DBMS access trough JDBC
  • Integration of JSP and Servlets (forward and include) using MVC pattern.

In addition, BD-review implements two Filters and plays with Regular Expressions.

Technologies Overview

• J2EE technologies (JSP, Servlets and JavaBeans)
• Database support (PostgreSQL 8.3) through JDBC 4
• XHTML Strict 1.0 + Cascading Style Sheets 2.1 for presentation
• Apache Commons for conversion and Bean population routines
• Some utility methods found on Books and Internet (their provenience is cited in the sourcecode)
• Javascript for confirmation system and form validation
• Regular Expressions
• TinyMCE rich WYSIWYG HTML editor

Screenshot: modifying a Review

Download

PDF report of the project
Complete Source Code and Documentation (as Netbeans Project)

The Future

There will not be future developments for the project. It was not a real-life project but I will be very proud if you find it an useful example for learning JSP. You can also use it as a basis for developing a real project (also a University Project). You can do anything you want with BD-review, but please respect the license. I would be happy if you send me an email about your experience in using BD-review.

License

BD-review is released under The Gnu Affero GPL version 3! This is different from the license of the contents of the blog

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program. If not, see < http ://www.gnu.org/licenses/ >.

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After the study of pointers versus references, the second natural question that comes in head of a ex Java developer turning to C++ is:

“What are the difference between static and dynamic memory allocation in C++?”

which can be translated as:

“When should I use the stack and when do I have to use the heap in C++?”

that can be further simplified to:

“When should I use the new operator in C++?”

I could simply summarize the answer to: “Use stack when possible”, but I think that this time there is the need of more explanations. Let’s have the following model for a process in the system:

A simplified model for a process

I’m not really interested in an real representation of a process (see Modern Operating Systems by A. S. Tanenbaum for a very good explanation on processes), but focus on the stack and on the heap.
In reality the heap is a software abstraction but you can also imagine it like the stack.
In C++ programs there are also several other memory areas in which objects and non-object values may be stored (see this article on GotW for further details).

Why then choose between stack or heap? Quoting my publication on object-oriented memory management in Java:

Stack-based variables have their extent determined by their scope, so the former is constrained by the structure of the code at compile-time .

Sometimes there is a need for the variables with unconstrained extent in order to cope with
problems where lifetime of a variable can only be known at run-time.
In this case heap-based variables, whose extent is strictly under control of the programmer, are used. [..]

I promise that I will update my 17 pages about OO-memory management to cover also C++ by the end of June. By the way, following some forums, wikipedia, my publication and GotW, I also summarized pros and cons of stack and heap use in C++:

Update 2009-07-03
After 4 months of heavy GUI and Database C++ programming, here are my thoughts: if you are planning to write a program with something more than a couple of objects interacting, using associations and therefore, objects as attributes, use the heap. Every serious program, even if not really big, uses heap for object allocation. Just take care to delete the objects when you don’t need them anymore. Objects on the heap are dynamically allocated and it is more comfortable to pass them through other objects using pointers. The use of the heap assures the live of objects even if the method that generated them runs out of scope ( =dies ). If you also plan to write GUIs, solid toolkits like QT recommend the use of heap to create graphical objects.

In some Operating Systems, stack is also very limited while heap is usually not.

Here are listed the sources I used for writing this article:

• http://www.velocityreviews.com/forums/t278261-stack-vs-heap.html
• http://www.computing.net/answers/programming/stackheap-c/2293.html
• http://www.codeguru.com/forum/showthread.php?p=1186307#post1186307
• http://www.codeguru.com/forum/showthread.php?t=350945
• http://www.gotw.ca/gotw/009.htm
• http://en.wikipedia.org/wiki/Process_(computing)#Representation
• http://task3.cc/object-oriented-memory-management/

Hope that this article helped you to clearly understand the differences between stack and heap allocation in C++, write me if there are other issues or you need more explanations!

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