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 consider 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 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 drawbacks 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's a client-server application - there is a browser (the 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 be determined by the architecture: different ones distribute the logic in various 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. Capability 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.  reformas integrales  of response from the server with minimum consumption of computation power.
Scalability. Ability to increase computation power or disc space under increases in amounts of information and/or number of users. In the event the allocated scalable system can be used, one must provide data consistence, availability and partition tolerance (CAP theorem). It is 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 on 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 find the application through any search engine.
Support. Expenses on app infrastructure - hardware, network infrastructure, maintenance staff.
Security. The software owner should be sure that both business data and information about users are kept secure. As the main security criterion we'll consider the possibility of changes in functionality of app behavior on the client side, and all associated risks. Standard dangers are the same for the compared architectures. We usually do not consider security on the 'server-client' channel, because all 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 purpose of the article is not showing what's good and what's bad. It's more of a detailed review that presents the possible options of preference.

Let's outline three main forms of web applications based on the roles performed by the server and the client browser.

Type 1: Server-side HTML

Probably the most widespread architecture. The server generates HTML-content and sends it to your client as a full-fledged HTML-page. Sometimes this architecture is named ''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 because there is a great amount of data transferred between the server and the client. The user has to wait before whole page reloads, giving an answer to trivial actions, for example, when only a portion of the page must be reloaded. UI templates on the 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. You can find no method of sending instant data updates or changes in real time. If we consider the possibility of 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 best of the three, since it's the easiest implementable. It's due to the fact that by default one URL receives particular HTML-content on the server.

SEO: 5/5. Rather easily implemented, much like the previous criterion - this content is known beforehand.
Speed of development: 5/5. This can be the oldest architecture, so it is possible to select 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 the moment when load balance will undoubtedly be needed. There's a a lot 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 necessary to generate data for the whole page (not only for the changed business data), and all of the accompanying information (such as for example 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 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 could 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. Usually 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's a more sophisticated variant of architecture). Thus one can wrap the application form in node-webkit or analogous means.