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We know things like buttons and panels are common to most languages, but are there any officially recognized and used recommendations or patterns for GUI APIs? (say, something from W3C maybe?)
I don't think there is a collection of what you are looking for. But in each of the frameworks you will probably find patterns that are applicable. Some might be specific to the runtime architecture that the API is built for but some are fairly general like MVC, Delegation or Decorator. Here are some links I know to appropriate architecture documents
Apple, Cocoa
Qt, General, Model-View Programming
Java, Swing (I don't know how old this is, haven't done anything using swing lately)
I have used a lot GUI frameworks over the last years and I still like the architecture that went into cocoa, it is one frameworks that implements guis in a very object oriented way. Most of the paradigms are applied consistently and repeatedly so that usually if you have figured out a way how to do things it will usually carry over to somewhere else.
I doesn't think there is any official and formal patterns from standard bodies. But there is a UI pattern catalog here. Yahoo also maintains a UI pattern library.
UI design is imho an art -- there's some "do this, don't do that", but not much.
Nonetheless designing-a-gui on SO
has some practical advice.
"Officially recognized": try Microsoft ?
Aspect-oriented programming is a subject matter that has been very difficult for me to find any good information on. My old Software Engineering textbook only mentions it briefly (and vaguely), and the wikipedia and various other tutorials/articles I've been able to find on it give ultra-academic, highly-abstracted definitions of just what it is, how to use it, and when to use it. Definitions I just don't seem to understand.
My (very poor) understanding of AOP is that there are many aspects of producing a high-quality software system that don't fit neatly into a nice little cohesive package. Some classes, such as Loggers, Validators, DatabaseQueries, etc., will be used all over your codebase and thus will be highly-coupled. My (again, very poor) understanding of AOP is that it is concerned with the best practices of how to handle these types of "universally-coupled" packages.
Question : Is this true, or am I totally off? If I'm completely wrong, can someone please give a concise, laymen explanation for what AOP is, an example of a so-called aspect, and perhaps even provide a simple code example?
Separation of Concerns is a fundamental principle in software development, there is a classic paper by David Parnas On the Criteria To Be Used in Decomposing Systems into Modules that may introduce you to the subject and also read Uncle Bob's SOLID Principles.
But then there are Cross Cutting concerns that might be included in many use cases like authentication, authorization, validation, logging, transaction handling, exception handling, caching, etc that spawn all the layers in software. And if you want to tackle the problem without duplication and employing the DRY principle, you must handle it in a sophisticated way.
You must use declarative programming, that simply in .net could be annotating a method or a property by an attribute and what happened later is changing the behavior of code in runtime depending of those annotations.
You can find a nice chapter on this topic in Sommerville's Software engineering book
Useful links
C2 wiki CrossCuttingConcern, MSDN, How to Address Crosscutting Concerns in Aspect Oriented Software Development
AOP is a technique where we extract and remove the cross cutting concerns (logging, Exception handling, ....) from our code into it’s own aspect. leaving our original code focusing only on the business logic. not only this makes our code more readable, maintainable but also the code is DRY.
This can be better explained by an example:
Aspect Oriented Programming (AOP) in the .net world using Castle Windsor
or
Aspect Oriented Programming (AOP) in the .net world using Unity
AOP is about crosscutting concerns i.e. things that you need to do throughout the whole application. For instance logging. Suppose you want to trace when you enter and exit a method. This is very easy with aspects. You basically specify a "handler" for an event, such as entering a method. If necessary you can also specify with "wildcards" which methods you are interested in and then it is just a matter of writing the handler code, that could for instance log some info.
Aspect Oriented Programming is basically for separating the cross-cutting concerns (Non-functional) and develop it as aspects, like, security, logging, monitor etc., kept it aside whenever you need in your application, you can use it as plug & play. Only benefit we can achieve is clean code ,less code and programmers can focus on business logic(core concerns) , so that better modularity and quality system can be developed.
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I try to be very cautious with this question. There are at least three different web-development frameworks available in Smalltalk. The most prominent seems to be Seaside but there is also AIDA/Web and Iliad.
They seem to be very similiar, but this impresson may be wrong. I wonder who has tried the different tools and can share the pros/cons of the different packages.
A more concrete question would be, do yo know of let's say any software in the bookkeeing area which has choosen to use either of the three (or other) web development frameworks.
Here's one other question. What about maturity and compatiblity. Which framework can one judge as the "most" stable?
99% of my practical experience is with Iliad, so my comparison is primarily about how I got to choose Iliad instead of the others.
Seaside. Tried it first, it is the most known and the first you stumble in. I found it hard to understand (as always, no matter what you use, when it gets to real implementation you always run into issues that fit badly with the general theory), there was little documentation around and the community seemed to care little about telling n00bs how to grow up. I eventually dropped it to check Aida. You find them here: http://seaside.st/ and on IRC at #seaside
Aida. I really liked it, as Janko is extremely patient and supportive. It is large, though. I decided to use it, when I was to start implementation for our project and it was only by chance that I ran into Iliad a few days before starting. You find Aida here: http://www.aidaweb.si/ and on IRC at #Aida
Iliad. The main reason I chose it was that I had just dropped Squeak and switched to gnu-smalltalk. gst seemed to have a lot of ongoing activity on Iliad, so I reckoned I was probably going to get a better assistance with it. It is much smaller as a concept (though it does absolutely everything) and I had very little trouble in getting started and in tweaking it to what I needed for. It also proved to be well managed, as I went thru 3 releases without ever being in trouble with what I had already deployed. You get answers to questions usually in 12-24 hours max, which is fine for me. You find Iliad here: http://www.iliadproject.org/index on IRC issues are usually channeled on the #gnu-smalltalk channel
What we are doing is a GUI for a PostgreSQL database used to manage a large multimedia dictionary, that in turn produces content (among others, for KDE-edu). I have no notion of booking apps in general, so I cannot answer to your question properly.
Yet, speaking as an analyst, a booking app is mostly a DB with an online GUI, so I see no reason why you could not make it. Much will depend on how easily your db can translate into objects. You could use a RDBMS, as we did, and design tables to map objects, or use an OODBMS. Both solutions have pluses and minuses, none of them is going to have an impact on your choice of framework, I'd say.
My suggestion is that you take a month or so in making experiments and see what better fits you. I don't think there is a tool that fits everyone, we are all different and what is easy for me may be hell for someone else (and the other way round, obviously). So try your car before buying it ;)
I would not invest too much time in studying the general theory. Using a smalltalk framework is going to turn upside down the way you make a web app anyway, and your first contact is going to be full of "false friends" you inherit from previous mindsets. Your best asset is definitely going to be "how quick can I grasp what they tell me", and this is largely an individual thing, depending on you and on who you bump into. So I'd really suggest you get your hands dirty BEFORE reading too much theoretical stuff.
These frameworks are all quite different and have different goals. It would be interesting to collaboratively create some kind of comparison.
As an author of Seaside I can provide the key properties of Seaside only:
Seaside makes building web applications feel like composing traditional GUIs: components can be freely composed and reused. Sequences of components are defined using a sequence of Smalltalk statements.
Seaside has a layered architecture, providing you with high-level abstractions (components, control flow, callbacks, HTML generation, JavaScript generation, ...) over low-level concepts (HTTP, Request, Response, URLs, HTML, JavaScript). If you need to, Seaside gives you full access to low-level constructs too.
There are two Seaside books to help you get started: Dynamic Web Development with Seaside and Seaside Tutorial.
Seaside provides a tight integration into various state of the art web technologies: JavaScript (JQuery and JQueryUI), SVG, RSS, HTML5, Comet (Server-Push)
Seaside runs identically on most today's Smalltalk platforms: Pharo Smalltalk, Squeak, GNU Smalltalk, GemStone Smalltalk, VW Smalltalk, VA Smalltalk, and Dolphin Smalltalk. It is supported by all vendors of Smalltalk platforms.
Seaside provides industry proven open-source components for meta-modeling (Magritte) and content management (Pier).
Let me introduce some strengths of Aida/Web too, because as its author it would be hard to me to compare with other two frameworks. Aida strengths are:
RESTfull URLs
MVC support, every domain object can
have its own RESTfull URL, each domain class has its own web presentation class,
Integrated AJAX and Comet
support, you don't see any difference
between a traditional and Ajax
programming anymore,
Tree-like control flow for GUI-like
control flows, without need for
continuations
Building web pages programatically by
composing from components/elements
(no template based)
Scalable in complexity and performance
Integrated security with access
control and users/groups management
Ported to most Smalltalk dialects:
Squeak/Pharo, VisualWorks, Gemstone
GLASS, Dolphin, Smalltalk/X
Prime and most fresh example of Aida at work is this year Smalltalk Google Summer of
Code site.
This is the is a nice example because it was developed it in maybe a week in
total, together with a development of GSoC process in parallel and in
the same time managing that process as an admin. This site is actually
an extended Aida/Scribo CMS, with strong use of so called scriblets,
that is, dynamic web "includes" directly into the content of the site.
That way I was able to very quickly support the new ideas which come
during the evolving GSoC process.
Well, Suixo uses Seaside. Take a look at the GSoC projects we defined. Its more ERP than bookkeeping, and currently focused on healthcare.
What are the improvements in vb.net compared to vb6 that make developing such an application easier?
I can think of a few:
ADO.NET is better than ADO for data access (and more options such as the Entity Framework, data repository blocks, LINqtoSQL)
better ability to structure your code for ease of maintenance because of better support for object oriented programming
better testability
overall a much better IDE
better handling of XML
richer set of interface choices: silverlight, WPF, WinForms, WebForms, ASP.NET MVC,
Web Client Software Factory
ASP.NET allows you to divide your interface code from your business logic much better by moving the logic into the code-behind file: better separation of concerns leades to easier and cheaper maintenance costs
WinForms has a much richer set of controls allowing you to build apps that are much easier for your users
better integration wilth other Microsoft products such as Sharepoint
This is by no means an exhaustive list. But it's at least a good starting point.
I switched to VB.Net because of LINQ. Everything else was a nice bonus. ^^
The ability to use the farking scroll wheel on my mouse in the IDE!
Sorry, had to vent on that one since I've recently been stuck in VB6 for maintenance on a legacy app.
I asked this question about Microsoft .NET Libraries and the complexity of its source code. From what I'm reading, writing general purpose libraries and writing applications can be two different things. When writing libraries, you have to think about the client who could literally be everyone (supposing I release the library for use in the general public).
What kind of practices or theories or techniques are useful when learning to write libraries? Where do you learn to write code like the one in the .NET library? This looks like a "black art" which I don't know too much about.
That's a pretty subjective question, but here's on objective answer. The Framework Design Guidelines book (be sure to get the 2nd edition) is a very good book about how to write effective class libraries. The content is very good and the often dissenting annotations are thought-provoking. Every shop should have a copy of this book available.
You definitely need to watch Josh Bloch in his presentation How to Design a Good API & Why it Matters (1h 9m long). He is a Java guru but library design and object orientation are universal.
One piece of advice often ignored by library authors is to internalize costs. If something is hard to do, the library should do it. Too often I've seen the authors of a library push something hard onto the consumers of the API rather than solving it themselves. Instead, look for the hardest things and make sure the library does them or at least makes them very easy.
I will be paraphrasing from Effective C++ by Scott Meyers, which I have found to be the best advice I got:
Adhere to the principle of least astonishment: strive to provide classes whose operators and functions have a natural syntax and an intuitive semantics. Preserve consistency with the behavior of the built-in types: when in doubt, do as the ints do.
Recognize that anything somebody can do, they will do. They'll throw exceptions, they'll assign objects to themselves, they'll use objects before giving them values, they'll give objects values and never use them, they'll give them huge values, they'll give them tiny values, they'll give them null values. In general, if it will compile, somebody will do it. As a result, make your classes easy to use correctly and hard to use incorrectly. Accept that clients will make mistakes, and design your classes so you can prevent, detect, or correct such errors.
Strive for portable code. It's not much harder to write portable programs than to write unportable ones, and only rarely will the difference in performance be significant enough to justify unportable constructs.
Even programs designed for custom hardware often end up being ported, because stock hardware generally achieves an equivalent level of performance within a few years. Writing portable code allows you to switch platforms easily, to enlarge your client base, and to brag about supporting open systems. It also makes it easier to recover if you bet wrong in the operating system sweepstakes.
Design your code so that when changes are necessary, the impact is localized. Encapsulate as much as you can; make implementation details private.
Edit: I just noticed I very nearly duplicated what cherouvim had posted; sorry about that! But turns out we're linking to different speeches by Bloch, even if the subject is exactly the same. (cherouvim linked to a December 2005 talk, I to January 2007 one.) Well, I'll leave this answer here — you're probably best off by watching both and seeing how his message and way of presenting it has evolved :)
FWIW, I'd like to point to this Google Tech Talk by Joshua Bloch, who is a greatly respected guy in the Java world, and someone who has given speeches and written extensively on API design. (Oh, and designed some exceptionally good general purpose libraries, like the Java Collections Framework!)
Joshua Bloch, Google Tech Talks, January 24, 2007:
"How To Design A Good API and Why it
Matters" (the video is about 1 hour long)
You can also read many of the same ideas in his article Bumper-Sticker API Design (but I still recommend watching the presentation!)
(Seeing you come from the .NET side, I hope you don't let his Java background get in the way too much :-) This really is not Java-specific for the most part.)
Edit: Here's another 1½ minute bit of wisdom by Josh Bloch on why writing libraries is hard, and why it's still worth putting effort in it (economies of scale) — in a response to a question wondering, basically, "how hard can it be". (Part of a presentation about the Google Collections library, which is also totally worth watching, but more Java-centric.)
Krzysztof Cwalina's blog is a good starting place. His book, Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries, is probably the definitive work for .NET library design best practices.
http://blogs.msdn.com/kcwalina/
The number one rule is to treat API design just like UI design: gather information about how your users really use your UI/API, what they find helpful and what gets in their way. Use that information to improve the design. Start with users who can put up with API churn and gradually stabilize the API as it matures.
I wrote a few notes about what I've learned about API design here: http://www.natpryce.com/articles/000732.html
I'd start looking more into design patterns. You'll probably not going to find much use for some of them, but as you get deeper into your library design the patterns will become more applicable. I'd also pick up a copy of NDepend - a great code measuring utility which may help you decouple things better. You can use .NET libraries as an example, but, personally, i don't find them to be great design examples mostly due to their complexities. Also, start looking at some open source projects to see how they're layered and structured.
A couple of separate points:
The .NET Framework isn't a class library. It's a Framework. It's a set of types meant to not only provide functionality, but to be extended by your own code. For instance, it does provide you with the Stream abstract class, and with concrete implementations like the NetworkStream class, but it also provides you the WebRequest class and the means to extend it, so that WebRequest.Create("myschema://host/more") can produce an instance of your own class deriving from WebRequest, which can have its own GetResponse method returning its own class derived from WebResponse, such that calling GetResponseStream will return your own class derived from Stream!
And your callers will not need to know this is going on behind the scenes!
A separate point is that for most developers, creating a reusable library is not, and should not be the goal. The goal should be to write the code necessary to meet requirements. In the process, reusable code may be found. In that case, it should be refactored out into a separate library, where it can be reused in the future.
I go further than that (when permitted). I will usually wait until I find two pieces of code that actually do the same thing, or which overlap. Presumably both pieces of code have passed all their unit tests. I will then factor out the common code into a separate class library and run all the unit tests again. Assuming that they still pass, I've begun the creation of some reusable code that works (since the unit tests still pass).
This is in contrast to a lesson I learned in school, when the result of an entire project was a beautiful reusable library - with no code to reuse it.
(Of course, I'm sure it would have worked if any code had used it...)