3 FORMS OF Web Application Architecture

Such terms as ”web app”, ”front-end architecture”, ”Web 2.0”, and ”HTML5 apps” have recently become trendy. Unfortunately these terms are often used 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 types of web application architecture in the light of the most recent web trends and key issues 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 types but they basically come down to these three as their subtypes.

First we’ll define a web application: it’s a client-server application – you will find a browser (your client) and a web server. The logic of a web application is distributed on the list of server and the client, there’s a channel for information exchange, and the data is stored mainly on the server. Further details depend on the architecture: different ones distribute the logic in different ways. It can be positioned on the server in addition to on the client side.

It’s near to impossible to judge these very different architectures impartially. But we’ll try to, using several criteria of evaluation:

Responsiveness/Usability. Updates of data on pages, switching between pages (response time). Such qualities of 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.

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 usage of computation power.
Scalability. Capability to increase computation power or disc space under increases in amounts of information and/or amount of users. In case 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, once 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 discover 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. As the main security criterion we’ll think about the chance for changes in functionality of app behavior on the client side, and all associated risks. Standard dangers are the same for the compared architectures. We do not consider security on the ‘server-client’ channel, because each one of these architectures are equally subjected to break-ins – this channel can be the same.
Conversion: site – mobile or desktop application. Possibility to publish the application on mobile markets or even to make a desktop application out of it with minimal additional costs.

Some of these criteria might seem inaccurate, but the reason for the article is not showing what’s good and what’s bad. It’s more of an in depth review that shows the possible options of choice.

Let’s outline three main forms of web applications according to 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 called ”Web 1.0”, because it was the first to appear and currently dominates the net.

Responsiveness/Usability: 1/5. The least optimal value among these architectures. It’s so since there is a great amount of data transferred between your server and the client. An individual has to wait until the whole page reloads, responding to trivial actions, for instance, when only a part of the page must be reloaded. contemporary houses templates on your client depend directly on the frameworks applied on the server. Because of the limitations of mobile internet and large sums of transferred data, this architecture is hardly applicable in the mobile segment. You can find no means 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 your 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 is actually the oldest architecture, so it is possible to choose any server language and framework for particular needs.

Scalability: 4/5. If we check out the generation of HTML, under the increasing load comes the moment when load balance will undoubtedly be needed. There’s a much more complicated situation with scaling databases, but this task is the same for these three architectures.

Performance: 3/5. Tightly bound to responsiveness and scalability in terms of 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 essential to generate data for the whole page (not only for the changed business data), and all the accompanying information (such as for example design).

Testability: 4/5. The positive thing is that there surely is no need in special tools, which support JavaScript interpretation, to test the front-end, and the content is static.

Security: 4/5. The application behavior logic is on the server side. However, data are transferred overtly, so a protected channel may be needed (which is basically a story 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 most cases it’s simply impossible. Rarely there’s an exception (more of exotics): for instance, if the server is realized upon node.js, and there are no large databases; or if one utilizes third-party web services for data acquisition (however, it is a more sophisticated variant of architecture). Thus one can wrap the application form in node-webkit or analogous means.

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