Hi Caleb, From my point of view, before starting to list technologies that would be great for a next generation XWiki you first need to define what your exact target is for XWiki. It is very important to do that because when I look at Jerome's answer I don't necessarly have the feeling he is looking at exactly the same objective as I would. While his technology choices might make a lot of sense for an eCommerce platform, they might not in the Intranet concept. This is a first big significant task which depending on the answers will serve as input on the technology stack to use. Indeed since 2003 when I started XWiki a lot of new technologies and also use cases or delivery methods have florished. For instance Cloud is now a very important delivery method of Web Applications and wether your write for a Cloud service, for Software deployment or for both this might lead to different technology choices. Mobile is another key delivery method that was not there in 2003. On the technology side, SOA, REST, Javascript are everywhere. NoSQL is also a key technology to consider. So let me first try to address the question of what a new XWiki could be used for, what it is currently used for, what are the strength of XWiki and it's weaknesses. First the initial objective which is the reason for XWiki: - building flexible collaborative intranets on top of a Wiki, allowing to quickly build applications, integrate these applications with the content Then a lot of things that users, clients have asked for, developers have done on their own: - providing Knowledge based solutions - building applications on top of the "Application" development features of XWiki (the extension of the previous use case) - providing a full Intranet solution, including what XWiki does natively, but also providing "Advanced Profiles", "Groups", "Social networks", a set of Collaborative Applications (Forum, files, etc..) - building public or internal content web sites with limited editors (CMS use case) - building a web application using XWiki as a framework, using many or little of the XWiki existing functions - just doing a very nice Wiki in an Enterprise or Public context - doing any of these in the "Cloud" context (multi tenant) and allowing users to subscribe to an "use-case" that would be built using the XWiki technology As you can see this is close to the "flavor" discussion we already have and I've voluntarily listed the first three which are the flavors we are currently discussing because this is at XWiki SAS what we see organizations we discuss with are asking for most. We have seen the other uses cases also but either we had difficulties addressing them or it was less natural to use XWiki to address them. The "framework" use case is a very important one here, because if we think XWiki's objective is to be a Framework objective for ANY web application, then this might be incompatible with the Intranet, Knowledge Base and even the Wiki use case. For instance Jerome's use case does not fit in the "Intranet" use case and the problem he has are very different from those you have in an Intranet environment. The "Cloud" one is a very big one also and can lead to radical different technology choices. As we can see many new cloud services are build around NoSQL and there are some good reason for that. It's because the Cloud provider wants a unique platform for all his customers and wants to run the service in a fully multi-tenant way on top of this unique storage mecanism. The objective here is to reduce the operating cost to the maximum, in order to be able to provide a "freemium" service. However this choice might have a lot of benefits in the "Cloud" context, but it is a radical choice which has a lot of impact if you also want to provide your service as "Software" like we do for XWiki. It complexifies the installation, reduces the features of your storage (very little relational queries), is a radical new technology to learn to build on which is still very young (choosen a NoSQL platform today is a very risky bet and supporting multiple technologies is a nightmare). Now not supporting NoSQL does not necessarly mean you cannot go "Cloud" but this goes against the way of doing business in the cloud and complexifies the cloud platform, has scalability issues, etc. Now it's impossible to ignore "Cloud" but it's important to understand which type of "Cloud". Is is a unique Cloud or is it SaaS where your objective is to be able to "host" the service for users and customers. The first choice might mean going NoSQL, the second might mean sticking with traditional Databases. The first choice might mean that you will have a hard time convince "software" users because you also need to convince them to go NoSQL. For me the biggest success we have is for "Intranets" and it has always been the key objective, and what we see is that the "Intranet" use case has lead us to have to address the "full Intranet" solution but also the "CMS" one as some organizations want a unique platform for both publishing and collaboration. There is a lot of pressure also to support all "Social Network" features as there are obvious bridges between a software that would be the main places to manage profile, groups and discussions and another software that want to manage information, knowledge and applications. For me the biggest strength of XWiki is it's flexibility to build Applications and to Customize it. The first objective of XWiki was to allow organizations to setup a wiki start sharing knowledge and then extend their wiki with applications that would organize the information in a better way. This need is still here today (Podio is a good example of the Application concept without the Wiki part to glue everything together). I believe many CMS include more and more "application" features so that you can extend your web site with more advance organizations and features (but CMS don't have the same collaborative aspects). The power of XWiki is to allow to do this fully from your web browser and to do it fast. It is to allow power users (not developers) to participate because they don't need full developer skill (this one is very important when it comes to the technology choices of how XWiki gets extensible). The power of XWiki is to not limit the customizations capabilities to the content but also allow to customize the UI by overidding all templates and then morph the initial web site you created into something else. This power is want allowed XWiki to kind of be a full "framework" for web development, but it could be that we have pushed it too far or not far enough. These strength are particularly talking for some of the users case listed before and for others it can actually be a weakness. The weaknesses of XWiki depend on the use cases. For the "Intranet" use case, our weaknesses have been to not work enough on the UI, to not adapt enough to the actual intranet use cases (this is where flavors come in). Another weakness is not enough separation (but not too much) between content and applications. Applications live in XWiki page but we don't have enough markers to separate them and not enough "SOA" at the XWiki Application level. We can fix this. Other weaknesses are how to address mobile, how to address AJAX development and still allowing power-users (not developers) to participate in this development. We also took too much time to build AppWithinMinutes. There are challenges to allowing power-users to develop and still allow this development to be continued by real developers. On the "framework" use-case it's another analysis. Do we need to allow development in the Wiki if XWiki's job is to compete with web-development frameworks ? Can we go without hosting the development in an IDE and if so should it be Eclipse or a Web based IDE ? Is it compatible to provide development features that are more easily accessible to non power-user (like velocity is) or can we go with more advanced technologies. Etc... there are many questions coming from that. There are many other very interesting questions that will yield different answers. For instance should we do a full AJAX UI. What are the consequences of it. If we go full AJAX, what about URLs ? What about search engine indexing. Can we do CMS if we are full AJAX. Full AJAX means more complex to customize also depending on how it's developped. To summarize we need to "choose" first what we want XWiki to be. Once we all agree on this then we can answer how to build the next generation XWiki. I don't disagree that we should think about this, because it's going to be 10 years in November since I started building XWiki and of course technologies evolve and we need to be able to adapt. I'm looking forward to your opinions on that. Then I propose we discuss for each of the use-cases we consider are the future of XWiki what are the right technologies. Then we also look at the compatibility of technologies with each other. This will give us a lot of answers. One being in which direction do we need to put our technological effort on. Another being more clear about what users and developers can expect from XWiki. Ludovic 2013/3/27 Jerome Velociter <jerome(a)velociter.fr>

My answer: XWiki is by definition "the wiki with features", one of the most important features is free-text search. The only serious text search solutions are written in Java so the JVM must be a part of my solution. I would use two layers of code, the bottom layer being a set of modules which do not have any means of communication among themselves so that can not become intertwined. The top layer shall be written in a popular scripting language and must be kept thin. I have reviewed Jython, Jruby, Groovy, and Node.js and gave cursory attention to Velocity, Scala, Rhino, and Clojure. I am a fan of Node and considered running a Node process external to the JVM but decided it is too difficult as it would require C++ to hook the garbage collection of "handles" in node and clear their associated Java objects. Velocity does not have the flexibility to represent models and controllers and I don't think Groovy has grown a large enough community. Scala is very interesting and might come up in the future, after all, Twitter is using it. There seems to be a solid community according to one popularity ranking[1] and it's syntax is quite beautiful by my standards. One can write functional code or imperative as they choose so the learning curve is reasonable. It has been faulted for long compile time. The build must be fast, otherwise developing is a pain. That said I will continue to watch it. We must always remember that even if our core devs like their IDEs, contributors who want to write one small patch will not want to spend hours importing XWiki so we must not make an IDE a requirement for developing. Clojure and Rhino are interesting but like Groovy, they don't have sufficient communities to get me excited. Clojure is very complete in it's vision but for people who are not familiar with functional programming, it's parenthesis soup. Python community is large and Django-on-Jython was a consideration but Jython is not getting much attention and it is said to perform poorly. Ruby performance is bad but it's said to be a reasonably well thought out language. It is one of the top ranking languages in terms of popularity so more users will feel at home, the Jruby engine is getting serious developer attention and the performance should be okay since most of the heavy lifting should be implemented in Java modules. I choose Jruby for the popularity but continue to watch Scala. For an MVC framework, I thought about Rails because it has the most community backing but I have been playing with Rails and found it to be overbuilt and reeking of jar hell. Sinatra to be far more simple so I would select Sinatra or a similar lightweight framework and possibly port to Rails later if need be. "how to run your Ruby webapp on the XWiki2 Platform" would get likely contributors excited who otherwise wouldn't care. I recently had the pleasure of working with HAML template engine which is a ruby-on-rails favorite. While I am quite impressed with HAML, I think Jade is even more complete in it's vision. Jade has been ported to Java so it should be faster than the Ruby implementation. http://jade-lang.com/ I choose Jade for the views. Storage ------- A central part of Ruby on Rails (or Sinatra) is the simplicity of ActiveRecord. Where Hibernate offers every option one could ever want, ActiveRecord offers the options that everybody is likely to want in a simple way. Using Jruby for the front end, ActiveRecord is the default answer and JDBC adapters for ActiveRecord on Jruby are available. Getting the Ruby defined model to be accessible to the Java code is a difficult problem but there has been some work on this front. http://blog.liveramp.com/2011/03/28/bringing-rubys-activerecord-to-java/ User defined model is the original killer app of XWiki and since the heavy normalization used in the current implementation poses some performance issues, I would have to generate native objects at the user's request and add and update the database tables on the fly to handle them. This is a technical challenge but not one which I think can be avoided. Where to put the data? Mysql? integrated HSQL/Derby? Hadoop? Cassandra? One thing I really don't want to deal with is customers who want to store the data in a weird backward database and then report bugs in my code because of problems they brought on themselves. I have a huge soft spot for Cassandra, it allows the code to scale to big data which we all know every enterprise has and just doesn't know it yet ;) Since it can be integrated in the JVM without very much hacking, it can keep the stack I test the same as the stack the user runs. This means getting ActiveRecord to talk JDO or to talk directly to Cassandra but the potential benefits are enormous: "The only wiki which can seriously scale" "Run your Ruby app in your own Cassandra cloud." Since this exercise didn't come with a budget or a timeline, I'm going to go long and say "integrated Cassandra node". My budget/timeline answer would have been Mysql. What will be Java ----------------- So far this sounds a bit like a total port to Ruby. What will stay in Java land? The answer is that heavy lifting and hot codepaths will be in Java since it's faster but the Java code will be designed to be generic in nature. Wiki syntax rendering and Jade templating will be in Java. Storage in Cassandra, search via Solr (or possibly ElasticSearch which I just learned about) and doc import and pdf export would be all in java (as extensions). Why will this not become a ball of mud? --------------------------------------- It should be easy to see why the java layer will not become a big ball of mud. Each module has no means of communicating with any other module. I have concluded that dependency injection is too dangerous to use on a project. In a well designed project DI provides little in the way of benefits but in a poorly designed project it acts as a Bank of Technical Debt, sweeping design problems under the carpet and allowing them to compound until the project becomes truly unmaintainable. For example: A dependency injector which allows Search module to pull in Permissions allows Search to: A: alter the state of Permissions in a way that causes a bug which can neither be seen in Search nor in Permissions alone but only in the two together. B: alter the state of Permissions in a way that causes a bug when Search is not present, creating a surprise dependency. Also my design would have no XWikiContext, no globally accessible thread local ExecutionContext or similar. All of these designs provide back channels through which modules can unintentionally communicate, leading to scenarios A and B. A module must only work with the tools which it is given by the code which called it. Why will the Ruby code not become a ball of mud? This is harder because it is the part which is designed to be easy to alter, it is easy to alter because most customization of the look and feel will be done here. Step 1: Use a framework, follow best practices for the framework. MVC, keep the logic in the controllers. Step 2: When controllers get too big (1000 lines), start finding code which can be moved down into the lower level. This is hard! You have a big controller filled with logic that calls modules like Search, Permissions, Database and Rendering and you have to subdivide the logic. You have to write new Search APIs for the Search code which can't touch Permissions, Rendering or Database. You can choose to write a wrapper module which wraps Search and Database and provides a richer API but your API must remain generic. If you are just rewriting the ugly controller in Java, you're pushing the dirt around. Suppose you don't keep up with it, what you get is a great big controller which is an eye sore and nobody likes it. You have obvious technical debt in one place. This is infinitely better than shoving the code down into some module which pulls in what it needs (wants) by dependency injection because then what you get is subtle technical debt accumulating in places all over the codebase. In place of dependency injection, I would use a single initialization script which lies on the boundary between code and configuration. This script constructs each module, feeding them their dependencies as they are constructed. This script is expected to look somewhat ugly, that's because any dependency problems will concentrate in this one place so it should be forgiven of some uglyness but watched as it is a metric of overall project health.

Thanks, Caleb [1] http://techcrunch.com/2012/09/12/javascript-tops-latest-programming-languag… On 03/26/2013 09:12 PM, Caleb James DeLisle wrote: _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs

On 03/27/2013 11:22 AM, Jerome Velociter wrote: http://blog.liveramp.com/2011/03/28/bringing-rubys-activerecord-to-java/ hacking, instances ? auto-wiring of components. Is this correct ? Hardwiring is not very cool but my main problem is that it allows for what the big ball of mud people call "Byzantine back channels that circumvent the system's original structure." EG: @Inject private ExecutionContext ec; ... ec.put("hack", somePieceOfInformation); ...later, in a "completely separate module".... @Inject private ExecutionContext ec; ... x = ec.get("hack"); This is a textbook case and it's obvious something is wrong but this pattern can be highly insidious. Seemingly innocent things like "putting the User object in the Session" create surprise communication channels which eventually make individual modules impossible to test without elaborate mocks and impossible to debug without taking in to consideration the state of the entire engine. The problem is if you put in place the systems to slay this monster, DI becomes far less useful so I would scrap DI entirely and accept the additional difficulty with designing such things as runtime extension loading. Thanks, Caleb http://techcrunch.com/2012/09/12/javascript-tops-latest-programming-languag… _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs