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 forms of web application architecture in the light of the latest 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 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 among the 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 styles distribute the logic in various ways. It can be positioned on the server in addition to 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. 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. Maximum speed of response from the server with minimum usage of computation power.
Scalability. Ability to increase computation power or disc space under increases in amounts of information and/or amount of users. In case 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 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 search engine.
Support. Expenses on app infrastructure – hardware, network infrastructure, maintenance staff.
Security. The software owner must be sure both business data and information regarding users are kept secure. As 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 are the same for the compared architectures. Chicago architects 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 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 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”, since 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 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 needs to be reloaded. UI templates on the client depend on the frameworks applied on the server. As a result of limitations of mobile internet and large sums of transferred data, this architecture is hardly applicable in the mobile segment. You can find no method 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 page, we’ll exceed this architecture.
Linkability: 5/5. The best of the three, since it is 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. This can be a 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, under 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 task may be 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 just 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 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 check 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 (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. 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 you can wrap the application in node-webkit or analogous means.