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 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 types 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 – 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 info is stored mainly on the server. Further details depend on 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 very 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 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 usage of computation power.
Scalability. Capability to increase computation power or disc space under increases in levels of information and/or number of users. In case the allocated scalable system is 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 the client app is increased at the program 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 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 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 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 exposed 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 from 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 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 your client as a full-fledged HTML-page. Sometimes this architecture is called ”Web 1.0”, because 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 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 instance, when only a portion of the page must be reloaded. UI templates on the client depend 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 no means 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 the client (through AJAX, WebSockets), plus design with partial changes of a page, we’ll exceed this architecture.
Linkability: 5/5. The highest of the three, since it is 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 a oldest architecture, so it’s 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 the moment when load balance will undoubtedly 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 regarding 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 necessary to generate data for the whole page (not merely for the changed business data), and all 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. Chicago architects is on the server side. However, data are transferred overtly, so a protected channel could be needed (that 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. Typically it’s simply impossible. Rarely there’s an exception (more of exotics): for example, 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.