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 are often found 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 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 styles but they basically drop to these three as their subtypes.

First we'll define a web application: it is 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 is a channel for information exchange, and the info is stored mainly on the server. Further details depend on the architecture: different styles 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 very 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 used.
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 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 is also worth noting that the case, once the number of features/screens of the client app is increased at the software owner's request, depends upon the framework and implementation rather than 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 should be sure both business data and information regarding users are kept secure. Because the main security criterion we'll consider the chance for changes in functionality of app behavior on the client side, and all associated risks. Standard dangers will be 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 form on mobile markets or to make a desktop application out of it with minimal additional costs.

Some of these criteria might seem inaccurate, but the purpose of the article is not to show 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 in line with the roles performed by the server and your 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 plenty of data transferred between your server and the client. An individual has to wait until the whole page reloads, giving an answer to trivial actions, for example, when only a portion of the page has to be reloaded. UI templates on your client depend on the frameworks applied on the server. Due to the limitations of mobile internet and large sums of transferred data, this architecture is hardly applicable in the mobile segment. There are no method of sending instant data updates or changes instantly. 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's the easiest implementable. It's because of the fact that by default 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. Here is the oldest architecture, so it's possible to choose any server language and framework for particular needs.

Scalability: 4/5. If we check out the generation of HTML, beneath the increasing load comes as soon as when load balance will be needed. There's a a lot 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 when it comes to traffic, speed etc. Performance is relatively low just because a big amount of data should 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 of 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. Generally 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 in node-webkit or analogous means.
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