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I would like some practical guidance on when I should use a Domain Specific Language. I have found resources about advantages and disadvantages, but what kind of project would warrant its use?
It seems like there is a big investment in time to create and maintain a DSL, so in what application space would I get a productivity return on my time investment?
Edit: It seems the most common use of DSL is for file formats for persisting data state, what about using a DSL for program logic and structure(perhaps code generation)? When is this feasible?
Edit #2 I am mainly asking about when is creating a specific DSL worthwhile. Of course we should use existing DSLs as much as possible to save time.
There are very few good reasons for creating yet another DSL. The world is fat with special-purpose languages.
Think along with these lines.
Solve the problem with a general-purpose language such as Python, Java, C++.. whatever.
Optimize that solution to factor out the common features and build a really nice, really elegant, really extensible class library.
Optimize that class library to emphasize "orthogonality". Make sure all features work well together, without any problems.
If you need simplification of the syntax only, create a scripting wrapper around your nice class library. This is your DSL. For Python, this is easy -- it's already a dynamic language. For Java, there are things you can leverage. For C++ it can be a bit of work to build this flexible scripting environment.
If you still need further optimization, consider writing a compiler for your DSL.
The ACM Computing Surveys article When and How to Develop Domain-Specific Languages provides advice on just this topic, as does Martin Fowler's 2010 book Domain-Specific Languages.
Firstly, I would use a DSL when the problem domain your developing against is a widely well known domain, and some business experts of that domain have already went through great lengths to build such a DSL so that you wouldn't have to go through the lengths yourself to solve all the problems they have already figured out.
If you're thinking of creating a DSL, I would consider doing so if your business is done in a very particular area, and you spend the majority of your time focusing in a specific problem domain. If you bounce around doing applications for multiple problem domains, then I wouldn't advise taking that approach.
For example, if your business is soley in building tax applications, it might be a good idea to build a tax system DSL. This would allow your language not only to be useable by you in your various tax applications, but it would also be marketeable (useable) by other businesses in your industry that want to do similar things that you're accomplishing.
Of course, you have to weight the costs/benefits of building a DSL vs a framework on top of an already existing language.
One situation that comes to mind is when the requirements requires a very high or improbable level of customization/configuration. So you would provide a kind of scripting model against a DSL instead.
Takes a car assembly "arm" for example, providing a configuration model to support various factory configurations would be impossible. (detect this, don't detect that, when this happens do this ... etc.)
But compiling a new application with specialized logic for each customer is probably not a good way to go. So in this case, you create a little framework that would becomes a kind of DSL, and then for each robotic arm you sells, you write a little app in your DSL and save it along with the core software that would compiles and runs your DSL scripts instead. Or better yet, tools to program the DSL are included along with the robotic arm so your customer can "program" the arm themselves in the DSL you created.
One real world examples that comes to mind is Yahoo Pipes (you could think of it as a DSL) or the robots.txt directive for automated web crawler for example. They may not be a full-blown DSL but they demonstrate where DSL might be useful.
Well, someone has to say it, so here goes:
Lisp is regarded by some as the domain specific language for any domain. A well-supported and very extensible DSL at that.
In some cases, fashioning a DSL from Lisp (or a similar language such as Haskell) could actually provide a lot of power with minimal effort, and thus would be quite worthwhile. DSLs do not always need to be big maintenance burdens.
The most obvious is you should definitely use them when the language already exists and is well-supported. The prime examples of this are UIL for Motif-based GUI development and make for software builds.
If you have to make your own, I'd say to look for domains a large amount of effort is in just specifying things properly, and where your compiler can't really find most errors, but a domain-specific compiler could. GUIs are a great example, as most of the work is in setting up the layout, and there are generally lots of ways to make syntacticly valid C++ calls that make no sense whatsoever to your underlying GUI system (EG: trying to embed an entire dialog widget inside a button).
I find UIL particularly a huge gain for GUI development because a UIL compiler can find errors in a GUI specification that just look like nice normal compilable code to a C++ compilter. The fact that it is well-supported means that the code is easy to port between platforms, and even GUI builders.
Related
Is it good architecture of an application if,
I am using multiple technologies leveraging strong points of each.
for example:
Encryption in python,
integration of services in java etc.
or should I stick to one technology like Java as I am comfortable with it?
Also the reason for this question is I am thinking of developing a new application in which speed is a major concern, I am targeting to attain.
Also Database that I am preferring for now is MongoDb.
Any suggestions on the Technologies apart from these technologies?
Also will this approach help in speeding up the application?
Writing the main application in one language only is a easier approach than dividing your application and attempting to write pieces in each language that is best suited for the task, unless you are fluent in a few languages and the ones chosen are particularly suited to specific groups of tasks that make up parts of the functionality.
Because MongoDB has a Java Driver there's nothing wrong with writing your main application in Java and relying on libraries written in other languages (MongoDB is written in C++, C and JavaScript).
As long as other works you need to rely on are well maintained there's no reason to switch from your preferred language to match what any of your libraries are using.
If you add artificial intelligence to your program in the future and part of the code is to run on a GPU you are forced to have a program that is a hybrid; learning a new language along with the details of the underlying algorithms is certainly more of a burden than learning the API.
Decide where to draw the line, what you will write in your preferred language and what will be written by others. It's certainly better to choose libraries and programs that you interface with written in languages you understand (assuming that they are open source). If what you interface with has no source available it becomes a 'black box' which simply must work, there are occasions when that is acceptable and occasional when there is no choice.
I'm a fairly advanced hobby programmer. I consider myself capable at Objective-C, Java, some straight C, Python, and general MVC design.
I've written quite a few programs but they have all been relatively self-contained, using external libraries occasionally.
When reading about larger projects, and/or more complicated programs, I hear a lot of language thrown around about "Writing one part in X, and writing this part in Y."
Since I have a lack of experience with this, I was wondering if someone could point me in the right direction. What general designs/mechanisms are employed for applications or projects written in more than one language? What is involved in a "scriptable" design?
Thanks for any guidance on the topic!
-Chase
There is no single "right way". A multitude of approaches exist, including the .NET-way, where all the languages are hosted inside a common runtime environment with well-specified interoperability constraints, and a good old Unix-way, where all the components are supposed to communicate via pipes or sockets, using simple text-based protocols.
For the latter you can read a classic book: http://en.wikipedia.org/wiki/The_Unix_Programming_Environment
Depends on what you need to do. For example if you want to build a poker game online then, most probably you would use java for the application and flash/flex for the interface. Java has the power of the libraries and the flash/flex are quite generally available and offer a rich interface.
If you have a software that receives input from an online application and offers output on a specific output (label printer for example) then your online-ready software (Java/PHP/Python) would best communicate with a specially designed program on the target computer. A program for which I'd use C++ for it's technical power, rigurosity and speed compared to java.
The idea is to identify the languages that suit your purpose best. In my opinion it is ideal that you use one language to do all the stuff, that is why I like java as it seems to fit everything although it has a more or less bad renown for slowness.
I see things in a kind of this way:
1. Engineered, machine oriented stuff then it is C++ (and languages of it's kind)
2. Mobile multifunctional stuff (middle-ware mainly) Java
3. Online , browser based stuff PHP especially for B2C(people oriented) applications
4. Python,Ruby etc are from my point of view somewhere between java and PHP but I never really worked with them so I can not give an exact opinion
You can link them together depending on your needs.
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The language site: http://processing.org/
What are people using Processing for? I have the opportunity to learn this in a classroom setting and am wondering if it will be a good use of my time.
Yes, it is useful and not a waste of time. I'm using Processing mainly for building proof-of-concepts for visualisations and graphic experiments. The time between an idea in my head and working code on my laptop is small, mainly because Processing does not throw too many obstacles in that course.
The ease of experimenting with things in Processing is an advantage in learning to program. Processing is actually a front-end to Java programs. At run-time the Processing code is translated to Java code.
Processing comes with a small but capable development environment (IDE), excellent documentation, a large library of extensions and a significant set of examples and demos.
Finally, I strongly recommend the book Processing: A Programming Handbook for Visual Designers and Artists by Casey Reas and Ben Fry, the authors of Processing. It's a beautiful book, carefully edited and full of sources for inspiration.
Processing has been used for hundreds of high-end projects in a wide range of fields, from multimedia installations to information visualization. It is not a toy or an educational exercise, despite its roots as a teaching tool.
The core application framework simplifies most common multimedia needs (OpenGL, Quicktime, PDF export, camera capture), removing project overhead involved in the boring task of setting up basic applications.It uses an extensible code structure that has allowed the creation of dozens of useful libraries for everything from 3D import / export to complex geometry synthesis.
So no, it is not a waste of time.
A references from my own work:
Stockspace
Anything that beautiful could never be a waste of time. :) It's probably the leading tool in its space, which would be something like, "Declarative languages for visualizing data". (Though I'm told it can do more than that.) Its got a O'Reilly book - that's always a great sign.
'Useful' and 'Beautiful' do not describe the library (processing is not a language), but the programs written in it. They are usually beautiful, but can be useful, too. Perhaps browsing it's showcase can give you a hint about some useful programs. Processing is very well suited for visualization apps, so it can indeed be useful for that.
Now, that's for the usefulness of the applications. For the usefulness of programming them, I think it's a pretty cool way to show more visually how some fundamental concepts of programs work, which you may find enjoyable. Processing is being used a lot nowadays to teach fundamentals of programming; it'd be cool to learn recursion by making fractals.
I have used processing for many interactive installations and found it really useful, because you get real fast results. Programming visual effects is really easy and elegant.
Some examples to watch:
http://www.youtube.com/watch?v=Ziv8Q5N7mSU
http://www.youtube.com/watch?v=zrT5uJox0J0
http://www.youtube.com/watch?v=Y58wBAp7mac
http://www.youtube.com/watch?v=EZp5HsFKxCs
http://www.youtube.com/watch?v=d4LcfsHQnYw
If you are dealing with a lot of data (many bitmaps, videos and sound) you might consider its limitations. I was happy to use it and will continue using it for certain projects.
So as a conclusion: processing is no waste of time. It's a really useful language for real world applications (in its own domain of course).
I agree with what the other posters have said, but I would add that every development tool has advantages and disadvantages. While it is easy to jump right in and visualize stuff with processing, the drawback is that it is hard to incorporate processing code into another project. Tools are in development to make this easier, but if you want a graphical environment that works in your application, all the time that processing saves you when prototyping is mostly lost in the re-adaptation of the code or getting it to work.
Processing is definitely useful for many purposes.
I think the post on "Processing for Programmers" by Eliot Lash answers your question very well, and in much detail. I'll give some highlights based on my experience below, but I recommend you have a look at the post, which also covers practicalities.
Your question has to do with the perception of Processing as a simple programming language and environment that doesn't require much experience to use. However, Processing is also a neat tool that makes life easier for more experienced developers, and the skills you develop with Processing can be definitely useful outside the "classroom" or prototyping contexts.
First off, as a programming language, Processing acts merely as a "layer" on top of Java that simplifies things. All Processing code is translated to Java code first. This means you can write Java code and import Java libraries in your Processing code, within (or outside) the Processing IDE. Pedagogically, this helps Processing serve as a "gateway" programming language into Java and other fully-featured languages. You can start coding with Processing, slowly make way into Java in a familiar environment, and then progress to more advanced tools.
You can also import Processing functionality into your Java projects (see here and here). This lets you exploit the speed and simplicity of Processing for multimedia etc., in the context of complex applications that require a more fully-featured programming language.
On top of these innate features, over the years, people have developed tools, libraries, etc. that can make your Processing skills useful in many contexts. Some examples:
Web/browser: Processing.js is a JavaScript library that lets you run Processing code verbatim in the browser. p5.js is a library for writing JavaScript based on Processing principles and functionality.
Mobile: You can develop Android apps using Processing by using the IDE in "Android mode".
Electronics, IoT...: The Arduino programming language and environment are very, very similar to Processing.
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I'm part of a group that starts a new development project from scratch.
Currently it is on hobby-basis but we aim to make it our living
in the time frame of 1-2 years.
We are senior developers coming from a multitude of languages and techniques
with much of the focus on Java for the last few years.
Now, we're thinking of choice of toolsets and languages (the future is
bright when starting from scratch).
We want to be able to use modern architectures efficiently and have
good experience in Java and other JRE-based techniques.
The project is in short a lot of I/O, databases and a decent UI that probably
needs to be web-based and feel quite efficient.
One route to go is classic Java and build UI using GWT (or layers on top of GWT),
another is Scala + lift.
Then there are other techniques based on Ruby, Groovy and so on.
My question is then: What would you select as tools for a new long-term
project given the above. Is Scala here to stay for instance or is one
of those with only temporary hype?
What other techniques do you consider for larger projects from scratch?
Possibly your biggest binary choice is whether you decide to stay on the Java Virtual Machine (JVM) via either Java or one of the other languages which compile into bytecode, or to move onto some other platform, possibly Ruby or Python (with the complications of working with different architectures/operating systems that this may entail). Personally, I decided that I very much wanted to stick with the JVM and hence your language choices would be...
Scala
All I can give is my own experiences coming from a Java background: migrating to scala was made easy by its natural integration into the Java ecosystem and the ability to continue to use pretty much the same toolset in the same way.
By this last point I mean that the statically-typed nature of scala means that all the refactoring and code-navigation opportunities are still available to the developer but scala's type inference means that this comes without the unnecessary verbosity of type declarations littered throughout your code.
I can still use my favourite stuff like Spring, ant, IDEA and I can still use all the libraries I've ever written in Java (this is an argument for picking a language which integrates with Java over a completely new one like Ruby, Smalltalk or Python).
From the perspective of whether scala is here to stay as a JVM language, this is what concerned me most. But consider how many questions on SO have been tagged Jython (161), JRuby (176), clojure (388) and Groovy (661), assuming you wish to stay on the JVM. Not only is scala now well ahead of these (815) but it is growing at quite a rate.
Lastly, although I have not used Lift, a colleague has been extremely impressed with it (and I would probably look at it if I were writing a web application). The fat-client alternative (scala swing) I have found to be more than useable (better than raw swing at any rate!).
Groovy
It's worth noting that the creator of Groovy recently said that had he known of the existence of Scala, he would never have bothered to create Groovy!
JRuby / Jython
I have lumped these two languages together because they both represent an attempt to port the syntax of a dynamic language onto the JVM. Unless that syntax is already familiar to you, why would you bother to go down this route? I must say, the SO stats (above) do not indicate that these have the momentum at the moment.
I would also opine that moving from a statically-compiled to a dynamic language is a big step and you might be surprised by what you miss (in terms of refactoring and development aides etc.) - you may also care about the fact that the interpreted nature of these languages makes them over an order of magnitude slower than Scala.
Clojure
I have no real opinions on clojure other than to say that with an imperative background, its syntax is scary and its flow extremely unfamiliar. I am becoming more impressed by the functional paradigm but I felt that clojure was a step too far for me; I would be a fish out of water in the language, having no previous experience of LISP/Scheme.
The choice of language implies a lot of other choices, which collectively can be more important than the language choice itself. More specifically, when you choose a language, you're also choosing that language's web framework, ORM, IDE, build tool, etc.
For example, if you choose Groovy, you're implicitly also choosing the Grails web framework, if you choose Scala you're choosing Lift, etc. Although you can use Eclipse/Netbeans/IntelliJ for almost any JVM language, the experience varies quite a bit depending on which language you're using. Eclipse is a great IDE for Java development, but a pretty crappy one for Groovy/Grails development.
The problem with this kind of question is that if you ask a guy who uses language X, he'll tell you to choose X, then list all the reasons why X is so great and a few shallow reasons not to use the other languages. Examples of such shallow criticisms include:
Scala
poor tool support
functional programming is esoteric to typical OO developers
Groovy
dynamic languages are unsuitable for large projects
dynamic languages perform poorly
Jython
whitespace indendation as code block delimiters sucks
dynamic langages (see above)
JRuby
reputation for bad performance
funky syntax (from the POV of a Java developer, at least)
Clojure
very funky syntax (from the POV of almost everyone)
very immature
I should emphasise that I don't necessarily believe any of the statements above to be true,
the point I'm trying to make is that it's very easy to dismiss languages without any real experience of them (I only really know one of the languages above). So I wouldn't put too much faith in what people say against a particular language, unless you're sure they've really used it.
If I was faced with your choice I would use Groovy/Grails, because I find it to be an extremely productive and enjoyable technology to work with for building web apps, with good tool support. Are there other choices that might be even better? Sure, but Groovy/Grails is good enough for me (for now).
If you all have strong Java background and no functional and/or dynamic languages background, then you are likely to do well by keeping to Java or migrating to Scala.
I don't mean to disparage any of the other languages here, but Scala will be more familiar to you, and you can put your Java familiarity to good use. Whether you should jump to Scala or not -- that's another question. If you do, however, take notice that you need not be stuck with Lift. Not only there are other web frameworks in Scala, but people have had success combining Scala with traditional Java frameworks such as Wicket.
I worked a lot with Scala, Groovy and JRuby and I can share my experience
Scala
This language was designed in a very in a professional way. You can see it in every aspect of it.
No performance issues because it is a static typed language.
Interesting to learn and play with because of its functional nature.
BUT:
It is very complicated. You can't spend an evening to write a hello world program. You should spend at least a weekend)) Dmitry Jemerov (one of the creators of IntelliJ) said that Scala is much more complex than C++.
Lack of a good tool support. I believe that IDEs for Groovy and Ruby is much superior.
Not well integrated into java ecosystem. Of course you can use java libraries but you will dance a lot of all conversions from one collection to another e.t.c.
Lack of pure Scala libs. You always have to write a small wrapper over a java lib.
Groovy
Has shortcuts for most java boilerplate code.
Great IDE integration.
Interactions with Java are so natural and easy. It is not important whether you use a java class or a groovy class, it just works.
Great for writing DSLs
BUT:
It is a slow language (But I think that it is not an issue in most cases)
As the integration with java is the main goal of Groovy there are some unnatural aspects of the language.
JRuby
One of the best designed languages I've ever seen.
There are a lot of cool libs that can be used.
The best language for writing internal DSLs
Easy to learn.
BUT:
The integration with java sucks.
In my opinion it is too early to use Scala in production systems. It is just too hard because of the lack of tools and libraries. I used Groovy in many big projects quite successfully so it may be the best tool from these 3 languages.
With the information given you can choose any language proposed. They will all still be here in 5 years.
If you cannot decide which tool to pick for your requirements we can't help you. The information given is just to vague to decide. Start building some prototypes for all language/framework and see what fits best. Maybe the requirements are more clear afterwards.
Have you tried Jython -- Python working on JVM? I use it quite often to do various database tasks and it works quite well with such databases as Oracle, PostgreSQL and Informix. I do not create classic UI apps, but I have read that well known Python Web frameworks like web2py or django work with Jython.
If you have experience using dynamic languages, and are able to write the unit tests to support them, go that way. The development speed should be greater than what you can achieve from a static language. However, as the project will get bigger, it may become harder & harder to mantain ( it may only be me, but compile time checks help you a great deal ).
If however, you have Scala experience, I'd choose that instead. I find Scala to be a nice mix between Java and Ruby.
Good luck!
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I'm facing developing a new web app in the future and I'm wondering how to decide what framework to use. I've settled on Python as my language of choice. But there are still may frameworks to choose from! More generally how do you choose between different similar technologies that are still in the works as the latest round of web frameworks are? I'm curious what your process is for deciding on technologies you've never used.
Recognize that no choice is perfect -- or even very good.
No matter what you choose, someone will have a suggestion that -- they claim -- is better.
No matter what you choose, some part of your tech. stack will fail to live up to your expectations.
The most important thing is "shared nothing" so that the components can be replaced.
After that, the next most important thing is automatically-generated features to reduce or prevent programming.
Look at Django. Lots of automatic admin features make life very pleasant.
There are a number of things you can do:
Download the frameworks and build something similar with them for comparison.
Look for comparisons by other people, but attempt to understand the bias of the reviewer.
Observe the community at work, see what people are building and the issues they run into when using the technology. Forums, blogs, mailing list etc are good places to check out.
Go to conferences and meet like minded developers interested.
You can also take the approach of using stable versions rather than alpha bits. After a while you might move closer the bleeding edge. People associated with the project in question are generally more biased than those approaching from other platforms, be careful who you trust.
Consider the impact of using a bleeding edge framework versus an established one. Sometimes it's important to your customers that you are on one perceived as stable. At other times this doesn't matter. How comfortable are you with fixing the framework itself? Great developers will learn the internals, or at least know enough to keep things moving whilst a bug is sent to the framework mailing list etc.
Consider some general best practices in building abstractions and reusable code on the python platform. You may be able to save yourself some work in moving to another platform. However, don't be a reuse junkie as this can limit the effectiveness of your use of the framework. The 37Signals guys are right when they talk about extracting frameworks from working code rather than building frameworks from scratch.
I know this is an old posting, but I am in a similar situation (again) and I think there are other people who may want to look for different opinions, and hear of (somewhat) successful experiences.
Since baudtack mentioned Python, I will try to answer this along the lines of my experiences using Python. Here is what has been working for me:
determine the scope of your project - outlining what your application is supposed to be able to do without introducing any programming or design notes will clarify your goals greatly
determine how you would like to work with your code, stack and data:
a. what sort of programming paradigm do you want to work with? i.e. object-oriented, functional, etc. do you want to play to your programming style or do you want to follow somebody else's programming style?
b. use semantic web or not? do you want greater control over URIs and their design? (I found web.py great for this by the way - It is my choice to create REST APIs in Python)
c. do you want to be trapped by framework requirements, or do you want a better separation of the application from the web component, i.e. use a framework to utilize your application as a set of modules, for example. My problem with Django was that I ended up not programming Python, but having to learn more Django than I needed to. If that works for you, then that is the way to go.
d. data stores... some sort of SQL vs. non RDBMS (xml databases like eXist-db with full xquery support) vs. OODBMS vs. a combination of the above? how complicated do you need this to be? how much control/separation do you need to have over how data gets stored and recalled in your application?
e. testing: unit tests... thank goodness for python! if your web app has the potential to grow (as they often do), having a sane and coherent testing platform to begin with will help out a lot in the future - I wish I had learned about this earlier on. oh well... better late than never.
f. how much control over the server do you need? hosting considerations? how much control over an Apache instance do you need to have? OS specific needs? I found that using shared hosting providers like Webfaction has been great. I eventually found I needed greater needs for flexibility and bandwidth. In other words, what can you get for your budget? If you have USD50 to spend each month, it may be better to consider a virtual hosting solution like Linode....
Finally, I echo S.Lott's sentiments that no choice for a solution is perfect, and are subject to obsolescence.
Experience trumps hearsay. I've found that prototyping is a huge help. Make a prototype that uses the features you expect to be the most important for various frameworks. This helps route out any features that may not work "as advertised."
In general though, kudos for being willing to look at new technologies.
I have a set of criteria in different categories:
Activity & Documentation
Is there an active user base?
Is there an active development base?
Is the support responsive and information accessible?
Are there user and development guides and reference material?
These are essential, there needs to be traceability of all of these to build confidence in the solution.
Ease of use
Are basic features easy and complex features possible? I typically give a new framework a test drive and try to roll out a set of use cases to see how intuitive the framework is to use.
Is installation intuitive and simple for a local/dev installation and production deployment?
How is it backed up and upgraded?
What is the effort and UX for implementing a "Hello World" type blog post, static page, menu item, and plugin?
How are versions dealt with for the core & plugins?
Example (on the topic of Automated Testing/Continuous Integration solutions)
Several years ago I evaluated several Automated Testing solution. At the time Jenkins and TeamCity were front runners and in the end I chose TeamCity because of the UX, active user & development base and quality of accessible documentation.
Example (CMS for a blog)
This criteria is also why I prefer to use Wordpress over other options. While wordpress has its shortcomings, the user and development base is strong and active which leads to a software architecture with more potential to evolve over time and maintain its relevance and a development community that provides quality plugins and themes to choose from.