Such terms as ”web app”, ”front-end architecture”, ”Web 2.0”, and ”HTML5 apps” have recently become trendy. Unfortunately these terms are often found in a misleading context which doesn’t consider the full specificity of implementation and usage of web app architecture. Today we’ll look for out more about the forms of web application architecture in the light of the most recent web trends and key conditions that matter to software owners.
We’ll outline 3 main forms of web architecture and discuss their advantages and disadvantages for three points of view: software owner, software contractor (developer) and end user. There can be other styles but they basically come down to these three as their subtypes.
First we’ll define a web application: it is a client-server application – there is a browser (your client) and a web server. The logic of a web application is distributed among the server and the client, there is a channel for information exchange, and the info is stored mainly on the server. Further details be determined by the architecture: different styles distribute the logic in different ways. It can be positioned on the server as well as on the client side.
It’s near to impossible to evaluate these completely different architectures impartially. But we’ll make an effort to, using several criteria of evaluation:
User:
Responsiveness/Usability. Updates of data on pages, switching between pages (response time). Such qualities of user interface as richness and intuitiveness in use.
Linkability. Ability to save bookmarks and links to various sections of the website.
Offline work. Speaks for itself.
Developer:
Speed of development. Addition of new functional features, refactoring, parallelizing the development process between developers, layout designers, etc.
Performance. Maximum speed of response from the server with minimum consumption of computation power.
Scalability. Ability to increase computation power or disc space under increases in levels of information and/or amount of users. In the event the allocated scalable system can be used, one must definitely provide data consistence, availability and partition tolerance (CAP theorem). It’s also worth noting that the case, when the number of features/screens of your client app is increased at the software owner’s request, depends upon the framework and implementation as opposed to the type of web architecture.
Testability. Possibility and easiness of automated unit testing.
Software owner:
Functional extendability. Adding functionality within minimal time and budget.
SEO. Users must be able to find the application through any internet search engine.
Support. Expenses on app infrastructure – hardware, network infrastructure, maintenance staff.
Security. The software owner must be sure that both business data and information about users are kept secure. Because the main security criterion we’ll think about the chance for changes in functionality of app behavior on your client side, and all associated risks. Standard dangers will be the same for the compared architectures. We usually do not consider security on the ‘server-client’ channel, because all these architectures are equally exposed to break-ins – this channel can be the same.
Conversion: site – mobile or desktop application. Possibility to create the application on mobile markets or to make a desktop application from it with minimal additional costs.
Some of these criteria might seem inaccurate, but the purpose of the article is not showing what’s good and what’s bad. It’s more of an in depth review that presents the possible options of choice.
Let’s outline three main forms of web applications based on the roles performed by the server and your client browser.
Type 1: Server-side HTML
The most widespread architecture. The server generates HTML-content and sends it to the client as a full-fledged HTML-page. Sometimes this architecture is named ”Web 1.0”, since it was the first ever to appear and currently dominates the net.
Responsiveness/Usability: 1/5. The least optimal value among these architectures. It’s so since there is plenty of data transferred between your server and the client. The user has to wait until the whole page reloads, responding to trivial actions, for instance, when only a portion of the page needs to be reloaded. UI templates on your client depend directly on the frameworks applied on the server. Because of the limitations of mobile internet and huge amounts of transferred data, this architecture is hardly applicable in the mobile segment. There are Fort Lauderdale architects of sending instant data updates or changes in real time. If we consider the chance for real-time updates via generation of ready chunks of content on the server side and updates of the client (through AJAX, WebSockets), plus design with partial changes of a page, we’ll go beyond this architecture.
Linkability: 5/5. The highest of the three, since it is the easiest implementable. It’s because of the fact that automagically one URL receives particular HTML-content on the server.
SEO: 5/5. Rather easily implemented, similarly to the previous criterion – the content is known beforehand.
Speed of development: 5/5. This can be a oldest architecture, so it is possible to choose any server language and framework for particular needs.
Scalability: 4/5. If we have a look at the generation of HTML, beneath the increasing load comes as soon as when load balance will undoubtedly be needed. There’s a much more complicated situation with scaling databases, but this may be the same for these three architectures.
Performance: 3/5. Tightly bound to responsiveness and scalability regarding traffic, speed etc. Performance is relatively low because a big amount of data must be transferred, containing HTML, design, and business data. Therefore it’s necessary to generate data for the whole page (not merely for the changed business data), and all of the accompanying information (such as design).
Testability: 4/5. The positive thing is that there’s no need in special tools, which support JavaScript interpretation, to test the front-end, and this content is static.
Security: 4/5. The application behavior logic is on the server side. However, data are transferred overtly, so a protected channel could be needed (that is basically a tale of any architecture that concerns the server). All of the security functionality is on the server side.
Conversion: site – mobile or desktop application: 0/5. In many instances it’s simply impossible. Rarely there’s an exception (more of exotics): for instance, if the server is realized upon node.js, and you can find no large databases; or if one utilizes third-party web services for data acquisition (however, it’s a more sophisticated variant of architecture). Thus one can wrap the application form in node-webkit or analogous means.