What exactly is Intentional Programming

StackOverflow https://stackoverflow.com/questions/201386

Question

On my reading spree, I stumbled upon something called Intentional Programming. I understood it somewhat, but I not fully. If anyone can explain it in better detail, please do. Is it being used in any real application?

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Solution

You got me started on this one...
Looks like C. Simonyi wanted to step to the next level of abstraction from High level languages. Reduce the dependency of customers on developers to make every change.. in code (cryptic for people not in development). So he invents this new product called IP, which has a WYSIWYG type GUI editor to create a domain specific model. (i.e. IP has a GUI to create the building blocks for your app.. LISP allowed you to create the meta/building blocks but not in a way that domain experts could easily do it.)
Like the models in UML, the promise is that you can auto-generate the corresponding source code at the "push of a button". So the domain experts can tweak the model in the future and press the Bake button to deliver the next version of the app. It seems to utilise DSLs however with the added benefit that multiple user-created DSLs can talk with each other via a built-in IP mechanism... which means the finance model and sales model can interact and reuse blocks as needed. As with DSLs, you get the benefit of code that conveys developer intent rather than appeases implementation language constraints.

The idea being to give greater control to the BA and domain experts who actually know what's needed...

Update: Real world use looks like 'not yet'.. although Simonyi believes 'absolutely in the long term'.
Short Story: MS squished IP in favor of .Net framework, Simonyi left MS and formed his own company 'Intentional Software'.. with the contract that he could use the IP ideas but he would have to rewrite his working proto from the ground up.. (that should slow him down). It's still Work-In-Progress I think.. and being written in C# (to boot)

Sources:

To think till yesterday.. I didn't know a thing about this. Investigative reporter signing off. Going back to day job :)

OTHER TIPS

It's the opposite of what happens when I come home at 2am after a pub crawl and fire up the laptop "just to check my email real quick, hon."

Then, the next day, when I peel open one eye and find my way to the bathroom at the crack of noon, I start brushing my teeth and realize, toothpaste dribbling out of my mouth, that last night I made 4 SVN commits, closed 3 bugs, and figured out how to solve the starvation problem on our distributed locking protocol. And I have no idea how the hell any of it works, anymore.

Or maybe it's what workmad3 said.

It appears to be a method of programming that allows the programmer to expand what is actually in the language to more closely follow their original intent, rather than forcing the programmers intent into the constrained syntax of the language.

It explicitly mentions LISP as a language that supports this, so I'd suggest you read up on this great language :) LISP Macros are exactly what are described in the article, allowing you to indefinitely expand the language to cover almost anything you would care to express. (A fairly common outcome of large LISP systems is that you end up with a domain specific language that is very good for writing specific applications, i.e. writing a word processor ends up with a word processor specific language).

For your last part, yes LISP (and thus Intentional Programming) is used in some projects. Paul Graham is a great proponent of LISP, and other examples of it include the original Crash Bandicoot (a game object creation system was created in LISP for this, including a LISP PlayStation compiler)

I have a slightly different understanding of Intentional Programming (as a more general term, not just what Charles Simonyi is doing). It is closely linked to fluent interfaces and can be achieved, with various degrees of difficulty, in modern Object Orientated languages.

Some of these concepts come from Domain Driven Design (in fact the term "fluent interface" has been popularised by Eric Evans, the author of "the" blue book - Domain Driven Design: Tacking Complexity in the Heart of Software).

The aim is to make business layer code readable by a non-programmer (i.e. a business person). This can be achieved by class and method names that explicitly state the intent of the operation. In my opinion, being explicit and being intentional produces highly readable and maintainable code.

Consider the two examples below that achieve the same thing - creating an order for a customer with 10% discount and adding a couple of products to it.

//C#, Normal version
Customer customer = CustomerService.Get(23);

Order order = new Order();
//What is 0.1? Need to look at Discount property to understand
order.Discount = 0.1; 
order.Customer = customer;

//What's 34?
Product product = ProductService.Get(34); 
//Do we really care about Order stores OrderLines?
order.OrderLines.Add(new OrderLine(product, 1)); 

Product product2 = ProductService.Get(54);
order.OrderLines.Add(new OrderLine(product2, 2)); //What's 2?

Order.Submit();

//C#, Fluent version
//byId is named parameter, states that this method looks up customer by Id
ICustomerForOrderCreation customer = 
  CustomerService.GetCustomerForOrderCreation(byId: 23); 
//Explicit method to create a discount order and explicit percentage
Order order = customer.CreateDiscountOrder(10.Percent()) 
  .WithProduct(ProductService.Get(byId: 34))
  .WithProduct(ProductService.Get(byId: 54))
  .WithQuantity(2); //Explicit quantity

Order.Submit();

By changing your programming style slightly, you are able to communicate your intent more clearly and reduce the amount of having to look at code elsewhere to understand what's going on.

Seems to me like yet another fad of software engineering. We've seen thousands of them already: meta programming, generative programming, visual programming, and so on. For a short time they get very fashionable, people use it everywhere, and then they invariably go back to old ways of creating software.

Why? Frederick Brooks has already answered this question over 20 years ago: there's No Single Silver Bullet to kill the werewolf...

Intentional Programming is encoding your intent, or goals. Thus it is Goal-Oriented Programming or Planning. Step up to manangement.

It's where you intend to program, you don't just accidently do it. ;)

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