3 Types 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 tend to be used in a misleading context which doesn't think about the full specificity of implementation and using web app architecture. Today we'll look for out more about the types of web application architecture in the light of the latest web trends and key conditions that matter to software owners.

We'll outline 3 main types of web architecture and discuss their advantages and disadvantages for three points of view: software owner, software contractor (developer) and person. There can be other types 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 exists a browser (the client) and a web server. The logic of a web application is distributed among the server and the client, there's a channel for information exchange, and the info is stored mainly on the server. Further details depend on the architecture: different ones distribute the logic in different ways. It can be placed 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 try to, using several criteria of evaluation:

User:
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 parts 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. Capability to increase computation power or disc space under increases in levels of information and/or number of users. In the event the allocated scalable system is used, one must provide data consistence, availability and partition tolerance (CAP theorem). It is also worth noting that the case, when the number of features/screens of your client app is increased at the program 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 in a position to discover the application through any internet search engine.
Support. Expenses on app infrastructure - hardware, network infrastructure, maintenance staff.
Security. The software owner should be sure both business data and information regarding users are kept secure. As  read my post 'll consider the possibility of changes in functionality of app behavior on your 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 could possibly be the same.
Conversion: site - mobile or desktop application. Possibility to create the application form on mobile markets or even to make a desktop application out of it with minimal additional costs.

Some of these criteria may 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 presents the possible options of preference.

Let's outline three main types of web applications based on the roles performed by the server and the 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'', since it was the first to appear and currently dominates the web.

Responsiveness/Usability: 1/5. The least optimal value among these architectures. It's so since there is a great amount of data transferred between the server and the client. An individual has to wait until the whole page reloads, responding to trivial actions, for instance, when only a section of the page has 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 large sums of transferred data, this architecture is hardly applicable in the mobile segment. There are no means of sending instant data updates or changes instantly. If we consider the possibility of 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 full page, we'll go beyond this architecture.

Linkability: 5/5. The best 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. It is the oldest architecture, so it's possible to choose any server language and framework for particular needs.

Scalability: 4/5. If we take a look at the generation of HTML, beneath 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 when it comes to traffic, speed etc. Performance is relatively low because a big amount of data should be transferred, containing HTML, design, and business data. Therefore it's essential to generate data for your 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 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 form behavior logic is on the server side. However, data are transferred overtly, so a protected channel may be needed (that is basically a tale of any architecture that concerns the server). All the security functionality is on the server side.

Conversion: site - mobile or desktop application: 0/5. Normally 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 you can wrap the application form in node-webkit or analogous means.