3 Why Carousel?
Carousel started life as a simple editor designed to make life easier for the developer. The XUI library had helped make construction of the user interface (UI) simple and in Carousel this had been extended to include many of the features needed to build rich enterprise level applications. The modular nature of the framework meant that inevitably there was some configuration required. Carousel was therefore born to assist in the setup and configurations of such applications. Over time Carousel has developed to include a range of advanced features and tools that ease the task of building modern applications.
Background
Carousel is a Java-based system that sets out to solve many of the problems encountered when building smart, client applications.
In its basic form, Java can be misused despite all its power. It also suffers from some shortcomings from the application developer's perspective: for example excessive plumbing is often required to perform simple tasks, no support is included for high-level abstractions such as the MVC architecture, and there is little high-level support for communication and data-access.
Many of today's client applications, be they built in Java or not, suffer from code bloat and poor maintainability. This problem largely derives from the use of IDEs and the throwaway nature of the code they generate. Unaddressed, this lack of emphasis on good design and quality leads to poor performance. For many, this is typified by the monolithic fat-client application, with all its deployment and maintenance issues. One common solution to these problems is to employ a thin-client architecture, moving processing to the server side and removing client administration woes, yet this solution is not without its own perils.
Despite the poor reputation gained by some client applications, there has been a resurgence of interest in smart client applications. Most client devices, even handheld devices, now have sufficient processing capability to perform useful work and this is wasted in a thin-client environment. Many of the fat-client problems have been solved and the thin-client solution is not the panacea that many had desired.
The XUI library at the core of Carousel is an open-source framework designed to solve some of the problems involved in building modern smart client applications.
Why do we build applications at all?
It may seem obvious to say that we build application to meet business needs, yet it is worth reflecting on the bigger picture. What do we hope to accomplish with our applications?
Typical requirements include getting the work done in an efficient and effective manner and having a reliable and maintainable system. All quite straightforward, but what about keeping the customer happy? Quite often the job is not just about getting the immediate business done but also about keeping the customers happy.
Many of today's applications fall short of providing an all round satisfying user experience. Frequently the user simply wants to accomplish the task at hand with the least amount of pain. At other times the user wants a richer, more informative experience, one that adds value.
Carousel can help you provide fast and effective client solutions.
The Form Metaphor
According to 2001 analyst estimates American businesses alone spend upward of $15 billion transferring data from paper-based forms such as loan applications and purchase orders to their computer systems. Billions more is invested every year in web based forms and other electronic forms. Not surprising when you consider the ubiquity of the humble form. Almost every business process involves form processing of one sort or another. In a broader view forms are an essential part of the data capture process for many businesses.
Electronic data capture and form processing offers many advantages over paper alternatives and act as the basis for a wide range of business applications. In many cases it may not even be possible to achieve comparable results with a paper based approach. Electronic forms can be of great value to both the end user (ease of use and error checking) and for backend processing (speed, quality and security).
Today a wide range of technologies are available for electronic forms processing. Many of the newer technologies are enabling completely new areas of automation and better, more functional applications. Couple this with other related technologies like mobile computing and wireless communication and you have many exciting new opportunities for improving workflow and communications.
From a business perspective automated form processing can bring many returns above and beyond the direct savings. The improved data can lead to better analysis of the customer relationship. Closing the enquiry-sales-fulfilment loop to manual data entry can even reduce leakage from the sales cycle. Where field workers or representatives are involved, faster more efficient technology will empower the employee.
In an application context the notion of a form can be quite vague but for the purposes of this guide we will assume that a form is a fairly discrete component that helps capture a subset of data. How that form is presented to the user can vary greatly within the definition of the user interface but from the point of view of the application logic the form's role is fairly well defined and helps for a logical subdivision of an application.
Beyond Forms
HTML forms have been the mainstay of web applications for some time. Although forms can be considered a workhorse of data capture, their use as the de facto user interface is not particularly well suited to the demands of modern business processes or for more complex application design. It is common for applications to comprise whole sets of forms and much of their value comes from relating the information on one form to another and to business intelligence.
It is easy to see that the smarter an application appears and the more responsive it is to the user, the richer the experience. Many of the web technologies in use today go to great lengths to provide such responsiveness and such intelligence, yet in many ways they face an uphill struggle. The infrastructure required to deploy some of these frameworks can be significant and rapidly pushes up the total cost of ownership despite what may be the obvious technical merits of an individual technology.
HTML was designed primarily for the display and linking of static text and static content. Extensions, plug-ins and many server side technologies have added to the power and capability of the basic HTML technology. The so called thin client that these technologies popularized has gained enormous popularity over the last few years. Despite the ubiquity and popularity of the thin client there are many areas where these web technologies have been less successful.
HTML's limits
An HTML application or form normally requires a request to the web server to provide updated content. Plug-ins or scripting may be used in some situations to avoid the round trip to the server and provide some element of local interactivity but often at the cost of complexity.
For anything other than simple applications the mix of HTML, JavaScript and server side technologies can rapidly lead to a complex technology solution. In many ways the solution is often more complex that the original problem. The more complex the applications become the greater the strain for these solutions to be effective.
Even without the implementation and delivery issues, HTML based applications suffer from the inherent delays associated with having to make frequent requests to the server. A simple round trip leads to noticeable delays in responding to user interaction and hence there is a limit to what is effective in terms of user interactivity with such applications.
Scripting
One of the defining characteristics of many web frameworks is the use of client-side scripting technologies. While scripting may be acceptable for small scale use it does not work well for large scale use. Scripting lacks many of the object-oriented features that programmers expect of a modern platform. Couple this to the common problem of separating roles with a environment that normally sees scripts embedded in user interface declarations and you can end up with a complex mess.
Underlying HTML's use is of course the browser, with all its security restrictions and compatibility problems. Even within an individual browser the lifecycle of a page can prove troublesome, making it difficult to maintain state. HTML is just not a natural fit for the needs of many modern applications.
Application delivery in a connected world
Today, a new range of connected workers has emerged, the road warrior, the business traveller, the salesman, the field worker, the PDA/Smart device owner. This type of user presents many new challenges. Typical of these demands is the occasionally connected nature of their usage. It's not much good to have smart devices if it is assumed that the application software needs constant connectivity, or if the applications cannot cope with loss of connectivity mid session.
Rich Client to the Rescue
Desktop computers and even the majority of mobile devices have significant computing power and therefore it is well within their capacity to handle much of what is delegated to the web server by thin client applications. One of the cornerstones of performance is locality of computing. Holding true to this maxim, locality of computing for a form application means that such things as data validation, prompting, user interaction can be handled locally. Doing things locally means not having to wait for a round trip to the server to complete. This alone can lead to faster, more interactive applications and interacting with data locally can also facilitate disconnected and mobile applications. Add to the local interactivity the rich user interfaces that can be built for today's rich client applications and you can get some very attractive applications.
So Why Carousel?
Carousel is a rich client application development platform designed to improve the way in which Forms and internet applications can be built. Bringing together two powerful technologies, Java and XML, Carousel offers many advantages in terms of ease of development, performance and portability. These advantages lead directly to reduced development and maintenance costs. The rapid development process that Carousel enables also means that you may have more time to devote to improving content and creativity.
The open source XUI framework addresses many of the problems discussed above and then some more. Carousel adds many additional widgets for building applications and business sector specific features and wizards, not found in the basic open source platform. Carousel also provides client-server support so that applications can more easily work within a corporate environment and communicate with back-end services.
Carousel comes with a feature packed editor and is built in an open way, supporting open standards. Vendor lock-in is avoided and the editor can be used in conjunction with other tools. So even if your authors and developers don't want to use low level technologies like XML they can build applications with the familiar drag and drop metaphors.
The Development challenge
For many organizations the move to thin clients was driven by administrative issues as much as implementation ones. The thin client was seen as a way of reducing administrative and helpdesk requirements as the client application had zero footprint. Furthermore the assumed ease of updating content was considered a major benefit in itself.
The penalty for this approach was that more responsibility was placed on the server side. All the users, all the user information and preferences had to be managed by the server. All the processing was shifted to the server as well. While architecturally this structure may have seemed simpler it often involved several tiers and a large array of systems.
The return of the rich client will not do away with many of the demands placed on today's servers but it will certainly reduce the load and in many ways simplify the applications. With each client managing its own state the server can be focused on providing the centralized enterprise level facilities to which it is best suited.
A rich client framework like Carousel implemented in a single language is considerably simpler than the highly layered approaches common in today's thin client systems. The problems that dogged rich clients of the past are but a memory. Zero footprint and incremental updates are a given. Security and a richer user experience are bonus.
Individual features of Carousel are worth using on their own not to mention using them in concert with other Carousel features. Take for example Carousel's method of constructing user-interface components via factories. This feature alone saves large amounts of code over what would be generated by a typical IDE. Carousel is a modular system so you can employ just one feature like this on its own, mixing and matching to your needs. Carousel, can therefore be integrated into new, old or legacy applications without difficulty. For legacy applications the Carousel framework can provide a convenient way of adding new and modern features to what may otherwise be tired looking applications.
Above all Carousel is designed by programmers for programmers.
If you were logged in you could rate this article or add a comment.
;)