Monday, 9 July 2012

OAuth protocol

In my previous post I write just a small definition about what OAuth protocol is. Today I'm going to try to explain Oauth Workflow, and therefore the work that I've been doing these last two weeks.

First of all, I am working following the OAuth 2.0. The reasons why I choose to work with the OAuth 2.0 protocol is because OAuth 2.0 is the next evolution of OAuth protocol, a lot of online applications (as Google) considers OAuth 1.0 deprecated, and most of java libs build to work with OAuth, in this case we are using Apache Amber,  do not implement Oauth 1.0.

Now let's take a look at the OAuth protocol basics.

OAuth defines 4 roles, which take part in the protocol:
  • Resource owner: an entity capable of granting access to a protected resource. When the resource owner is a person, it is referred to as an end-user.
  • Resource server: the server hosting the protected resources, capable of accepting and responding to protected resource requests using access tokens.
  • Client: an application making protected resource requests on behalf of the resource owner and with its authorisation. The term client does not imply any particular implementation characteristics (e.g. whether the application executes on a server, a desktop, or other devices).
  • Authorisation server: the server issuing access tokens to the client after successfully authenticating the resource owner and obtaining authorisation.

Let's take a look to OAuth work flow:

OAuth 2.0

The OAuth Client  register itself  in the Authorization Server, as result it will respond with a consumer key and with a shared secret.

The authorization code work flow diagram involves the following steps:
  1. Client obtains request_token: 
    a. The client requests authorization from the resource owner.
    b. The authorization request can be made directly to the resource owner (as shown), or preferably indirectly via the authorization server as an intermediary.
  2. Resource owner authorises request_token:
    c. The client receives an authorization grant which is a credential representing the resource owner's authorization, expressed using one of four grant types defined in this specification or using an extension grant type.
    d. The authorization grant type depends on the method used by the client to request authorization and the types supported by the authorization server.
  3. OAuth Client exchange its request token for access_token:
    e. The client requests an access token by authenticating with the authorization server and presenting the authorization grant.
    f. The authorization server authenticates the client and validates the authorization grant, and if valid issues an access token.
  4. OAuth Client uses its access_token to obtain protected resources:
    The client requests the protected resource from the resource server and authenticates by presenting the access token.
    The resource server validates the access token, and if valid, serves the request.

I've been working with Amber, I had problems trying to include the library in the project and meanwhile I was working the developers changed pretty much the library. The danger of working with a incubator project. Anyway, it's already working.
Sadly I could not find a good documentation about how to write a provider using this library, so if anyone in the community knows about it please share it in the comments, I would be really grateful.

Finally, my mentor, Carl Hall, helped me to understand some principles about OSGi than I had confused. Thanks! :)

I'll keep working in the OAuth Provider, just remember you than you could follow my work at github.
Any comments will be welcome, and any Amber tutorial too. :)

Saturday, 23 June 2012

Oauth integration: First month report

Summer is on, so it's code time. Hooray!

Beginnings are always harder, but the first development month have passed (as my finals) and I would like to speak about what I've been doing so the Sakai community will be updated properly. First of all, I must thank my mentor, Carl Hall for his work.

Now, let's talk about the project. Let's begin with the basic, this is the Oauth definition that we could find in the Wikipedia:
OAuth is an open standard for authorization. It allows users to share their private resources (e.g. photos, videos, contact lists) stored on one site with another site without having to hand out their credentials, typically supplying username and password tokens instead. Each token grants access to a specific site (e.g., a video editing site) for specific resources (e.g., just videos from a specific album) and for a defined duration (e.g., the next 2 hours). This allows a user to grant a third party site access to their information stored with another service provider, without sharing their access permissions or the full extent of their data.
We can easily realize how useful it is for Sakai Nakamura to have an Oauth provider. It will allow third part applications, as native mobile apps, access to private resources to the users, useful isn't? Moreover, the community has already identify this need here [0]

 This first month I've been working basically in setting up the development environment, and learning about Oauth protocol. I was planning to write a tutorial with my notes but this tutorial [1], it's really useful. Anyway, if the spanish-speaking community will find it useful a translation of it, leave a comment and I will write it happily. Also, I fork Nakamura repository and I began to write the skeleton of the Oauth Client and Oauth Server (right now it's just an hello world), you can follow the development here [2].

I hope you are interested about the project, I would like to hear some feedback. And if you have anything to ask or suggest me, please do not hesitate.

By the way, happy Turing's day :)

[ 0]

Friday, 2 September 2011

GSoC pencils down

Congratulations to our successful GSoC students Aadish, Mai and Kasun on completing GSoC, and for their excellent contributions to Sakai.  It's been a pleasure working with you. 

Unfortunately it's 'pencils down' for the official project, and all that remains is to collect the T-shirt and to plug Sakai at the GSoC Mentors' conference at Google HQ in Mountain View.  Carl Hall will be ably representing again this year - don't forget to take Sakaiger stickers Carl.

Carl is also going to be taking over from me to admin Sakai GSoC next year, provided Google continues to support this excellent programme, so watch this space for an exciting new chapter.

Tuesday, 23 August 2011

Summer and HBase!

I spent most of my summer dealing and learning Hadoop’s column database called HBase. Why this database? To put in Ian Boston’s words : “The reason for HBase is its the DB of choice for many systems that want to do large scale data analysis on Hadoop.” Ian declared that the choice of database was HBase on June 27 and since then, I must have clicked more number of links on Google for ‘HBase’ than perhaps the number of HBase deployments itself! Then started the quest of mine, to reconsider database driver in light of this new database, and code for the tests which would judge its performance. After a plethora of idea exchange the code was written and tests were implemented. This post aims at explaining and shedding some light on deployment of HBase as how I had done it during the summer.

World, HBase. HBase, world.

People coming from RDBMS background, just shake your head vigorously, and forget all the schema that you have ever implemented in your life! To absorb concepts of HBase, just vacuum clean your head and make room for new concepts to flow in.

Why HBase?

To answer that question I’ll have to walk you through the problems of traditional databases. Traditional databases face basically two types of problems: First is scaling and the second one, well, can be called ‘sparse-ity’. Traditional RDBMS may be reliable, widely used, developer friendly blah blah blah, but when you ask it “How do I scale you”, it would reply “Put more money in me and buy more hardware”. The second problem can be addressed thus: Imagine you are trying to stuff an intricate object graph, with many interdependent objects and relations into RDBMS schema. Definitely, you are bound to end up with a schema wherein an object may have several attributes, which well, may be seldomly used. Your RDBMS surely is going to charge you for all those extra ‘NULL’ references out there! So how does HBase deal with this, lets see!

HBase and scaling :

HBase is specialized column DB(more on it soon), mastered in scaling. It partitions horizontally and ‘distributes’ data over huge number of commodity servers. HBase is built on Hadoop , which implements functionality similar to Google's GFS and Map/Reduce systems. It provides means to efficiently organize and serve huge amount of data. If you are more interested read Google’s BigTable Paper and Map/Reduce concepts.

HBase and ‘sparse-ity’:

HBase is a column oriented database. This means that it stores contents in form of columns rather than rows. This frees up the need of attributes which may not be necessary for an object. In row DBs, where you would have nineteen NULLs and one attribute, HBase(or rather any column DB) would only save that one attribute. So, less room for storage, and high speed performance!

HBase datamodel:

An excellent read for this would be :

How I went about setting up HBase for SparseMapContent:

Configuring Apache HBase database on Windows:
The page describes how to configure Apache HBase in a standalone mode on Windows using Cygwin.

For Windows environment, 3 technologies are required which are JAVA, SSH and Cygwin.

Installing JAVA:
Download the standard Edition JAVA plateform from here and follow the simple GUI wizard to install the same.

Installing Cygwin
Cygwin provides *nix like environment in Windows. Steps for installation are as follows:
1. Make sure you have Administrator privileges on the target system.

2. Create Root and Local Package directories. A good suggestion is to use C:\cygwin\root and C:\cygwin\setup folders.

3. Download the setup.exe utility from here and save it to the Local Package directory.

4. Run the setup.exe utility,

1. Choose the Install from Internet option,
2. Choose your Root and Local Package folders
3. and select an appropriate mirror.
4. Don't select any additional packages yet, as we only want to install Cygwin for now.
5. Wait for download and install
6. Finish the installation
5. Add CYGWIN_HOME system-wide environment variable that points to your Root directory.
6. Add %CYGWIN_HOME%\bin to the end of your PATH environment variable.
7. Reboot the sytem after making changes to the environment variables otherwise the OS will not be able to find the Cygwin utilities.
8. Test your installation by running your freshly created shortcuts or the Cygwin.bat command in the Root folder. You should end up in a terminal window that is running a
Bash shell. Test the shell by issuing following commands:

1. cd / should take you to the Root directory in Cygwin;
2. the LS commands that should list all files and folders in the current directory.
3. Use the exit command to end the terminal.

9. When needed, to uninstall Cygwin you can simply delete the Root and Local Package directory, and the shortcuts that were created during installation.

Installing SSH:
HBase (and Hadoop) rely on
SSH for interprocess/-node communication and launching remote commands.

1. Rerun the setup.exe utility.
2. Leave all parameters as is, skipping through the wizard using the Next button until the Select Packages panel is shown.
3. Maximize the window and click the View button to toggle to the list view, which is ordered alphabetically on Package, making it easier to find the packages we'll need.
4. Select the following packages by clicking the status word (normally Skip) so it's marked for installation. Use the Next button to download and install the packages.

1. OpenSSH
2. tcp_wrappers
3. diffutils
4. zlib
5. Wait for the install to complete and finish the installation.

Installing HBase
Downlaod HBase from here, unzip it and place it under the directory C:\cygwin\usr\local\ so that it gets installed in Cygwin(C:\cygwin\usr\local\hbase-)

Configuring JAVA
1. Create a symbolic link in /usr/local to the Java home directory by using the following command and substituting the name of your chosen Java environment:
LN -s /cygdrive/c/Program\ Files/Java/ /usr/local/

2. Test your java installation by changing directories to your Java folder CD /usr/local/ and issueing the command ./bin/java -version. This should output your version of the chosen JRE.

Configuring SSH
1. On Windows Vista and above make sure you run the Cygwin shell with elevated privileges, by right-clicking on the shortcut an using Run as Administrator.

2. First of all, make sure that the rights on some crucial files are correct. Use the commands underneath and you can verify all rights by using the LS -L command on the different files. Also, notice the auto-completion feature in the shell using is extremely handy in these situations.

1. chmod +r /etc/passwd to make the passwords file readable for all
2. chmod u+w /etc/passwd to make the passwords file writable for the owner
3. chmod +r /etc/group to make the groups file readable for all
4. chmod u+w /etc/group to make the groups file writable for the owner
5. chmod 755 /var to make the var folder writable to owner and readable and executable to all

3. Edit the /etc/hosts.allow file using your favorite editor (why not VI in the shell!) and make sure the following two lines are in there before the PARANOID line:

1. ALL : localhost : allow
2. ALL : [::1]/128 : allow

4. Next we have to configure SSH by using the script ssh-host-config. The following may be asked in random order but don’t worry about that.

1. If this script asks to overwrite an existing /etc/ssh_config, answer yes.
2. If this script asks to overwrite an existing /etc/sshd_config, answer yes.
3. If this script asks to use privilege separation, answer yes.
4. If this script asks to install sshd as a service, answer yes. Make sure you started your shell as Adminstrator!
5. If this script asks for the CYGWIN value, just as the default is ntsec.
6. If this script asks to create the sshd account, answer yes.
7. If this script asks to use a different user name as service account, answer no as the default will suffice.
8. If this script asks to create the cyg_server account, answer yes. Enter a password for the account.

5. Start the SSH service using net start sshd or cygrunsrv --start sshd. Notice that cygrunsrv is the utility that make the process run as a Windows service. Confirm that you see a message stating that the CYGWIN sshd service was started succesfully.

6. Harmonize Windows and Cygwin user account by using the commands:

1. mkpasswd -cl > /etc/passwd
2. mkgroup --local > /etc/group

7. Test the installation of SSH:

1. Open a new Cygwin terminal
2. Use the command whoami to verify your userID
3. Issue an ssh localhost to connect to the system itself
1. Answer yes when presented with the server's fingerprint
2. Issue your password when prompted
3. test a few commands in the remote session
4. The exit command should take you back to your first shell in Cygwin
5. Exit should terminate the Cygwin shell.

8. If you get stuck with some password problem, you can change it using the command passwd.

Configuring HBase

(2nd and 3rd steps are optional.)
1. HBase uses the ./conf/ to configure its dependencies on the runtime environment. Copy and uncomment following lines just underneath their original, change them to fit your environemnt. They should read something like:

1. export JAVA_HOME=/usr/local/
2. export HBASE_IDENT_STRING=$HOSTNAME as this most likely does not inlcude spaces.

2. HBase uses the ./conf/hbase-default.xml file for configuration. Some properties do not resolve to existing directories because the JVM runs on Windows. This is the major issue to keep in mind when working with Cygwin: within the shell all paths are *nix-alike, hence relative to the root /. However, every parameter that is to be consumed within the windows processes themself, need to be Windows settings, hence C:\-alike. Change following propeties in the configuration file, adjusting paths where necessary to conform with your own installation:

1. hbase.rootdir must read e.g. file:///C:/cygwin/root/tmp/hbase/data
2. hbase.tmp.dir must read C:/cygwin/root/tmp/hbase/tmp
3. hbase.zookeeper.quorum must read because for some reason localhost doesn't seem to resolve properly on Cygwin.

3. Make sure the configured hbase.rootdir and hbase.tmp.dirdirectories exist and have the proper rights set up e.g. by issuing a chmod 777 on them.

Testing the installation and configuration of HBase on Windows using Cygwin.
1. Start a Cygwin terminal.

2. Change directory to HBase installation using CD /usr/local/hbase-, preferably using auto-completion.

3. Start HBase using the command ./bin/

1. When prompted to accept the SSH fingerprint, answer yes.
2. When prompted, provide your password. Maybe multiple times.
3. When the command completes, the HBase server should have started.
4. However, to be absolutely certain, check the logs in the ./logs directory for any exceptions.

4. Next we start the HBase shell using the command ./bin/hbase shell

5. You can run some simple test commands

6. Leave the shell by exit

7. To stop the HBase server issue the ./bin/ command. And wait for it to complete. Killing the process might corrupt your data on disk.

8. In case of problems,

1. Verify the HBase logs in the ./logs directory.
2. Try to fix the problem.
3. Get help on the forums or IRC ( People are very active and keen to help out!
4. Stop, restart and retest the server.

Getting the code using git
Open the GIT bash or command prompt and follow the following commands:

$ cd
$ mkdir sparsemapcontent
$ cd sparcemapcontent
$ git clone
$ cd sparsemapcontent/
$ maven clean install
$ exit

For developing the code in eclipse

1. Import sparsemapcontent folder as existing maven project.
2. Include the following jar files into the project in case they are not there from /usr/local/hbase- folder.
· Hbase-.jar
· Hbase--test.jar
3. Start the HBase server as stated before.
4. Create the tables au, an, cn and smcindex.

So that was how I dirtied my hands in HBase. It’s a great DB to understand column DB concepts. I hope this was helpful.

Please feel free to mail me at Hopefully your mail would put me in a tizzy!

Also interested readers may ponder over the matter in these site:

1. Configuration of HBase :

2. HBase data model :

3. HBase book :

4. HBase on Windows OS :

5. Place to start learning about Hadoop :

6. HBase debugging and troubleshooting :



Sunday, 14 August 2011

Sakai OAE Native mobile app: almost the end.

It is almost the end of the summer of code, (time flies!), so this post will be just a quick summary about how the project is going on, because I want to use all the remaining time to finish some code, add new features and write documentation.

So this is just a sneak view, to keep the community update. Again, I must begin this post thanking my mentor Carl Hall, for his hard work, he has asked every question that has arisen and also he gave me some freedom to make take some decisions. So, thanks Carl! I am really proud to work with you :)

Ok, let’s focus on what matters. If you read my previous post (Why should I develop native mobile application (sometimes)?), one of the bad things about writing native applications is the maintenance, when I wrote this post I have already complained about the problems of implementing functions in one platform that are completely different in the other. I have been stuck in a lot of device specific problems, I tried my best to take benefit of the iOS and Android user interface, so the layout is slightly different in this two apps.

I am going to quickly enumerate things that are already implemented:

  • Skeleton application for Android : It has grown up a lot since last time I talk about it. It has 3 tabs for the main features in Sakai OAE that they match with the 3 main tabs on Sakai web version. Also it has the navigation menu inside “You” tab. All the strings than you can see are internationalized.
  • Skeleton application for iOS: idem in IOS. It took me a lot of time make it work. As you could see in the demo tabs are in the lower part of the screen, to use the UI specific tabs, and make the application easier to use for iOS and Android users.
  • Authenticate users in Android and iPhone: last time I wrote I had users could authenticate themselves sending their credentials in Android. Right now they can do the same also in the iOS application.
  • Store and manage Sakai URL in Android: Carl and I were thinking than write down every time the Sakai URL was really tedious. So we add a new first view where the user writes the URL, the app checks if it’s a valid URL and store it inside the device. In Android it is stored inside the SharedPreferences of the app, so we can get the URL every time we needed it.
  • Store and manage Sakai URL in Android: same for iOS. Here the URL is stored in a singleton class inside the NSUserDefaults.
  • Calling a web service and show data in Android: Although the authentication was already a web service, we have achieve to call the Me Service with the user credentials, get back the Basic Information inside a JSON Object, parsing it, populate java classes and showing the information inside the Android App. Apache has really useful libraries to do this.
  • Calling a web service and show data in iOS: again the result for iOS is the same, but the implementation has nothing to do, here I used JSONFramework to parse the data and Objective-C classes to manage the connection. This web service is inside a thread so it runs in background.

And since a picture is worth a thousand words, I have uploaded a small demo video to youtube.

I hope you find this project interesting. Thank you for your time and I’d be waiting for your comments.

Saturday, 13 August 2011

Sakai CLE Mobile Application using phoneGap and jQuery mobile.

After a long time I think I should write something here as this will be the last or one before the last opportunity to write in the Sakai Google Summer of code projects blog.

Last month or few weeks was really a hard time because the things I had to handle were almost new to me and almost all the cases were issues and my mentor was getting so many mails with the title * issues (this is a regex) examples would be “Localhost issues”, “Cross domain issues” :-).

I think discussing solutions for them would be really worthy because when I googling also what I noticed in some places was “21 users has this question (Stackoverflow)” so I was the (n+1)th person to have same question.

First issue raised just after the last post because as I discussed in that I was using JSONP feeds from the server to render application on mobile but due to security reasons JSONP feeds were stopped and I was in trouble. When I searched I note that the solution is JSONP and having a proxy sever both are not going to work for mobile application as JSONP support also no longer there. But all these restrictions are for http:// and https:// protocols I realized later with the help from my mentor. Because as we are developing the application using phoneGap and it uses file:/// protocol there is no such restriction to get JSON feeds from a remote server so finally the problem solved. For completeness here is a snippet.

Next the issue with localhost, when we are going to test application with emulator (in my case Android) when it sees localhost with in the emulator (device) it is looking for a localhost inside the emulator and eventually failed to find. So I had to use my friends laptop as my dedicated Sakai server. But for mac users I saw a solution here [1] but I can't try it out. Though phoneGap wiki has something like this [2], I could not get it working, please correct me if I am wrong by adding a comment.

Next the very immediate issue I had was ajax requests that were in different pages to not working. The issue is like this, I used all the ajax requests in doument.ready event in different htmls but as jquery mobile uses ajax is used to load the contents of each page into the DOM as we navigate, and the DOM ready handler only executes for the first page. [3] So instead of DOM ready, in jquery mobile, we have to bind the pagecreate event in order to execute the code when the page is loaded and created by ajax. Note that the above snippet is using pagecreate. And one more thing I noticed most of the places is to use data-role=page and create new pages without adding a new HTML this will increase the loading time of each page as well. Use separate HTMLs if you really need only and if you are not happy with the pagecreate you can just use rel=”external” flag with your link like this,

but this will stop you by using page transition effects like slide and all and currently there is no way to get the effect with this.
And finally, I would like to add some screens that we can see in the application.

"This will be the view of a profile for an user in sakai CLE. User details are categorized in to sections as we can see and they collapsible too. Moreover users can update their status on the go via @sakaimobile :-)"

"This is how an user will see what are the new alerts from different tools in a selected site. We will, most probaby, be supporting Announcements, Assignments, Forums and Roster tools." Note that un-supported tools are grayed out. And users can see how many new alerts are there from each tool.

At the beginning as I said this will be the last or one before the last post in this blog but one day I might be writing here again but as a proud *mentor* for an student of Sakai foundation, who knows? :-)
Add you valuable comment and correct me if there is anything I have mentioned wrong. Thank you all for giving this opportunity to write in this blog and thanks to my mentor for guiding me and help me in all the issues I had.
Next week will be for any documentation stuff, if there are any, and correct the application where necessary to work with different devices.

Thursday, 28 July 2011

Why should I develop native mobile application (sometimes)?

When we faced the question about if we should develop a web mobile application or a native mobile application, there is no universal answer (although sometimes, reading some articles, it seems there is one). When we begin a new development, first of all we must begin with a requirements analysis and functionalities that we are going to implement, and based on these we can make decisions. Just like when an architect designs a building, does not arise if there are good or bad materials or techniques, the architect just think if these materials or techniques are suitable for this particular work. We should think about every developmet independently and carry out a specific analysis for the application we will develop (otherwise the bogeyman will come and he will take away all our work, developers
who worked during the software crisis will tell us that this is true).

The purpose of this post is to analyze the case of developing a mobile application for Sakai OAE, of course, this is my analysis and I will be happy to rectify any mistake or any approach that can be wrong. Anyway, if you are interested in something more generic, google is our friend, simply search for "native apps vs web mobile" and you could spend all evening reading tons of articlees about this subject.

During this GSoC, two mobile applications are being developed for Sakai, and each one follows a different approach. I sincerely believe that both decisions are correct. I'm sure that Kasun Lakpriya and Steve Swinsburg who are developing the web-based mobile application for Sakai CLE, will give you plenty of good reasons why a web application makes sense to Sakai CLE. I'll focus on Sakai OAE.

Sakai is a young web application OAE, based on well-recognized standards, such as ajax or json, its design completely revitalizes the user experience by improving the workflow for both teachers and students. It is a highly scalable application that is developed following best practices ... It is definitely a really cool a web application. In fact, thanks to the hard work being done by the ux team, we can browse the web application using a mobile device and the application still will look really nice. So, in my point of view, since we have a good web application that with small changes may well be a mobile web application, it makes more sense to try to take advantage of the possibilities that native applications will give us.
And what these possibilities are? Well these are some of them that we could use in Sakai OAE, but certainly these aren't the only ones:

  • Connectivity (Off-line mode): Although it's becoming less common, not all places have a good Internet connection, in Spain from where I write at least this is so. And web applications need, obviously, Intenet connection to work (even though we can achive some things with html5 and Google Gears). So being able to have the application running all the time is an advantage, we won't lose an alarm that warning us a deadline of a job, or stop reading some content because we don't have an Internet connection.

  • Improve the user experience: Native applications, in general, improve the user experience, not only by the performance they can achive, but to use elements of the user interface of the device itself, although, of course this can also be emulated. It is also very interesting the possibility of having the application running in the background and receive certain notifications, as twitter apps do.

  • Device-based caching:Certain information could be store encrypted on the device itself, which is very useful for improving the user experience, not forcing him/her to introduce the same data each time.

  • Using the device features: This property could seem a bit strange in case of an educational application, but if you think about it is not. For example, when a teacher creates an activity, he/she could not only tag the date and time whe the activity will be done, also it is possible to introduce aGPS address indicating the place where the activity is take place, which is really helpful if we think about field practices, especially large campus or for students with no spatial orientation (this is my case). And surely we could imagine a lot of creative utilities using phone services such as the agenda or the camera. Why should we limit it?

  • Discoverability: It's really easy to find an application in the market / app store.

  • Performance: This is, in my opinion, the jewel in the crown of native applications. We can develop threads, use devices notifications, and make the application run in the background... And in the case of our application, where normally users turn on the app early in the morning when they arrive to university and they won't turn off until they go home, this is a very interesting feature to exploit.

Although there are also mobile applications features negative, we can see the positive side of these (or at least, do not consider them so negative)

  • Automatic Updates: Web applications are updated automatically, while in the case of native applications we should upload them to market/app store and wait util the user updates them. This is initially a point for Web applications, but from my point of view, this is not so negative for Sakai OAE. The mobile application of a large university, must be stable and not constantly updated unless absolutely necessary (I'm thinking of a security bug), so we shouldn't worry too much.

  • The censorship of the market/app store: I have write market/app store because I don't want to not arouse suspicions, but really where the applications pass quality tests and can be rejected is at the appstore. Again, this seems quite negative, but an application is rejected by quality issues primarily (or duplicate a service of IOS, which is not the case), which obliges us to work hard on the quality of the application, and Apple is not particularly ambiguous on how we should develop applications. If we'll see it this way, I honestly do not think it's an inconvenience at all.

And since not everything could be so beautiful, there are features that are inherently negative (if you can see a positive side please tell me!):

  • Reaching the audience: Although Android IOS and monopolize the market for mobile devices, these are not the only platforms, which makes our mobile applications fail to reach the audience. But as I mentioned in the introduction, Sakai OAE is a good web application that can be accessed from any mobile browser.

  • Maintenance: This really is a handicap. A native application implies that we must develop at least two projects for IOS and Android, and the rise of Windows Phone makes me think than maybe for this one too. This multiplies the cost of development and maintenance. I'm developing it for IOS and Android, and I suffer the problems of implementing functions in one platform that are completely different in the other, I can not deny this. Some months ago I was naive because I though that the development and maintenance costs would be lower since both apps are restful applications and the same web services are called. Anyway, Sakai community is big and great and I think the advantages outweigh the disadvantages.

I don't mean that web applications can't work as native applications. And every day we will find new frameworks to simply the work and get better performance.

To summarize, I don't think there is no good or bad answer about what kind of app develop. This is my analysis, and of course there are many nuances to all the features I've listed, I won't be surprise me if I'm completely wrong in more than one point, so I encourage you to leave me any comment with your thoughts and talk on here or IRC #sakai where you can find me as AdaHopper.