Announcing Opa: Making Web Programming Transparent

phy_si_kal writes "Opa, a new open source programming language aiming to make web development transparent, has been publicly launched. Opa automatically generates client-side JavaScript, and handles communication and session control. The ultimate goal of this project is to allow writing distributed web applications using a single programming language to code application logic, database queries and user interfaces. Among existing applications already developed in Opa, some are worth a look. Best place to start is the project homepage which contains extensive documentation, while the code of the technology is on GitHub. A programming challenge ends October 17th."

Comments

very expensive to implement

[Tumbleweed]

Every time you do something in Opa that is successful, you have to break a plate. Opa simply isn't economical to scale.

How is it different from, say, Wicket or ZK?

[Cyberax]

How is it different from, say, Wicket or ZK, or even GWT?

I can write complete AJAX-y webapps in Wicket or ZK, including database. They both store state of pages on server side, so AJAX becomes trivial (just rerender the page and send the difference in DOM trees using JSON).

Then there's GWT which compiles static Java code into JavaScript.

Obigtory.....

[Anonymous Coward]

This seems to be getting some use lately.....

For me as a German

[Anonymous Coward]

this language seems to be obsolete from the beginning.

Re:Which open-source license?

[ludwigf]

AGPL 3

Probably the most important implication of AGPL is that it requires you to provide a way for your users to download the sources of the application. In fact Opa facilitates that by automatically enriching the server (in release mode) to serve the source code of the application at a special /_internal_/src_code URL.

But this is not the end of the story. We believe in free software (hence the AGPL license) but we also understand that it may not be very suitable for commercial users of Opa. Such users will be able to obtain a private license (paid). This will allow them to keep their sources closed if they wish to do so and will provide us with funds to further develop and improve Opa — win-win situation :). If you are interested in more details about obtaining such a license, do not hesitate to contact sales@mlstate.com, where we will try to answer all your questions (including pricing).

http://blog.opalang.org/2011/08/opa-license-contributions.html

So here's some example code

[moonbender]

No idea whether it's viable long-term, but I thought it's really interesting. It does way more than GWT does, for example. It's also statically typed, yay.

Here's some example code from the tutorial. This is a chat room. Apart from CSS, this is the entire soure code required to create the chat room server. Yikes. Had to get rid of the comments to appease the spam filter, unfortunately.

type message = {author: string /**The name of the author (arbitrary string)*/
              ; text: string /**Content entered by the user*/}
 
@publish room = Network.cloud("room"): Network.network(message)
 
user_update(x: message) =
  line = <div class="line">
            <div class="user">{x.author}:</div>
            <div class="message">{x.text}</div>
        </div>
  do Dom.transform([#conversation +<- line ])
  Dom.scroll_to_bottom(#conversation)
 
broadcast(author) =
  do Network.broadcast({~author text=Dom.get_value(#entry)}, room)
  Dom.clear_value(#entry)
 
start() =
  author = Random.string(8)
  <div id=#header><div id=#logo></div></div>
  <div id=#conversation onready={_ -> Network.add_callback(user_update, room)}></div>
  <div id=#footer>
        <input id=#entry onnewline={_ -> broadcast(author)}/>
        <div class="button" onclick={_ -> broadcast(author)}>Post</div>
  </div>
 
/* Main entry point. */
server = Server.one_page_bundle("Chat",
      [@static_resource_directory("resources")],
      ["resources/css.css"], start)

Wt

[paugq]

Why is a new programming language required to "make web development transparent"?

Opa automatically generates client-side Javascript and handles communication and session control. The ultimate goal of this project is to allow writing distributed web applications using a single programming language to code application logics, database queries and user interfaces

Wt does exactly the same but in C++. You develop webapps like desktop apps: widgets, ORM, etc. No need to care about Javascript, HTML, etc. Compilers available on all platforms. The result is a single binary which includes an embedded HTTP(S) server.

While I agree with what Opa wants to achieve, inventing a new programming language for that end is unnecessary and, in fact, will become a burden: they will need to maintain both the language and the library. But actually the value lies in the library, which is the one that needs to deal with HTTP, Javascript, AJAX, etc

Re:Wt

[phy_si_kal]

You're the debian packager for Wt, so you must know Wt much better than I do. However, both projects are very different and you should probably have a real look at Opa before popping up on every story about Opa (followed by another comment by someone else saying the link was useful, history repeats ;). Opa is high-level language for writing web apps. Wt is a toolkit for writing web components in C++. There is an order of magnitude between the length of application code in Opa and in Wt. Wt handles everything as strings and does not perform any verification on the soundness of the application -- it's a way simpler project. But on the other hand it is useful to add a web touch to existing C++ desktop apps.

Re:yes!

[mellon]

Yes, and if Javascript weren't so bloody limited, that would be a great solution. Why, oh why, couldn't they just have embedded Scheme, which has all the wins of Javascript, and none of the limitations? Sigh.

Dear Creators of Opa...

[drgroove]

Dear Creators of Opa - Honestly, what were you thinking? Opa is basically another crack at the same approach that ColdFusion tried years ago, and failed at. Opa isn't Object Oriented, meaning that developers working in an OOP language (Java, .NET, Python, PHP, Ruby, Perl, etc) will have a tougher time making the transition - it also means that Opa can't implement or support standard Design Patterns, which is a huge mistake IMnsHO. The sample code on the Opa site shows a mix of Opa functions, database interaction, markup language, CSS, Javascript... what a mess. Haven't we all learned that clean separation of functional application concerns is the only way to write scalable, enterprise-class programs yet? Opa doesn't appear to support any database beyond it's own build-in, slightly obfuscated one, meaning it will gain no enterprise/business traction. As much as I like to see new programming languages succeed, I have to agree w/ a lot of the other posters on /. - Opa is dead on arrival.

Re:Dear Creators of Opa...

[Seferino]

Dear drgroove,

Thank you for your considerate feedback.<sarcasm mode="off"/>. While we understand very well the drawbacks of Opa not being Object-Oriented (at least not in the usual meaning of the term), there are several reasons for this choice. The first and most important of these reasons is that experience from 15+ years of experienced developers writing scalable systems with Object Oriented Programming Languages, and concluding that OO is not the right paradigm for the task, and that other paradigms need to be hammered upon OO languages to make them scalable. Rather, when designing Opa, we decided to choose a paradigm not on its popularity, but rather on its suitability for the task of writing highly-scalable, highly-secure, highly-dynamic web applications. This paradigm is comparable to that of Erlang or Scala. Certainly, this requires leaving the comfort zone of OO and putting all these learning neurons back to work, and certainly not all developers who have tried Opa have liked it, but direct and indirect feedback seems indicates that most did – a lot.

The second reason is more complex. We have experimented with OO in Opa and our experience shows that, to obtain the same level of security guarantees we achieve at the moment in an OO language, we would have had to abandon either lightweight programming (and require type annotations in many places), automated client-server distribution (and require site annotation just about everywhere) – theoretical sidenote: if you wonder, a large part of the problem is related to open recursivity in a structural setting, a nasty topic in particular when some methods depend on untrusted code.

Haven't we all learned that clean separation of functional application concerns is the only way to write scalable, enterprise-class programs yet?

We have worked very hard to permit separation of functional application concerns in Opa. Our tutorials and samples focus on conciseness, which is why it is a bit hard to see, but it is possible, and if we find time and resources to proceed in this direction, future versions of Opa will go much further along the way. However, I concur that this is one of the areas we could improve most (other ones being error-handling, the default UI toolkit, and expanding the database access primitives). So if you have any suggestion, really, we are quite interested. The current project lead can be reached at Mathieu.Baudet@mlstate.com and I am certain that he will be eager to hear about your ideas.

Opa doesn't appear to support any database beyond it's own build-in, slightly obfuscated one, meaning it will gain no enterprise/business traction.

Actually, at low-level the current version of Opa does support a few additional databases, but this is something that we do not publicize yet as we are certainly going to make changes before we are satisfied with the feature. As for enterprise/business traction, well, let's start with non-enterprise/business developers and work our way up :)

Yours truly,

the architect-in-chief of Opa.

Re:Integrating everything into one thing?

[Seferino]

Integrating everything into one thing seems like a poor idea. Sure, it makes it a little easier for the dev, but in the end, you are just learning 5 times the amount of Opa when you could learn each thing.

Well, that's not quite true. Having the same language for database manipulation and for in-memory manipulation is a huge time-saver. Having the same language (indeed, the same piece of code) for server-side validation and for client-side validation is more efficient and less bug-prone. And you have only learnt one thing.

Not only that, but can one thing really do all those tasks the other things do, and do it as well? Even if it can, it's harder to keep all of those on a level, you can't replace those parts if you find something better. It just seems to me that splitting things down into the parts seems like something we should be doing, not reversing.

Ok, on this, you may have a point.

I also really don't like the whole compiling to JavaScript behaviour. Maybe just because I don't like JavaScript.

Well, that's part of the point: with Opa, you do not need to write any JavaScript.

Caveat I'm part of the Opa team. Well, worse than that, I'm the architect-in-chief.

Re:needs time

[Anonymous Brave Guy]

I think you're misunderstanding the concern. If I build my code using GCC, then GCC itself may be open source under whatever licence, but my code is mine to license as I wish. If you follow the link I gave above, you'll find that the Opa guys think that not only Opa itself but also anything you write with it should be forced open (by their definition of open, which is different to almost anyone else's). That's the kind of policy that gets abrupt from corporate lawyers saying "Put this within 50 miles of our network and you're fired". It's also incompatible with many other popular OSS licence policies.