Our dependence and reliance on Web applications have significantly increased due to their importance in information exchange and business transactions [9]. In this sense, flow plays a central role in Web applications since it affects the user behavior towards them [12]. Flow is a state which occurs when navigating in an information space and which is intrinsically enjoyable, self-reinforcing and accompanied by a loss of self-consciousness[11].
In his work, Oinas-Kukkonen [12] modified the general flow concept into a Web-specific construct: “Webflow is an optimal perceived user experience which improves a web user’s orientation and navigational use, as well as vice versa, and which is predicted by balanced user skills and the feeling of the web to be enjoyably challenging, the feeling of being in control of web use, and the perceived ease of use and usefulness of the web”. In this sense, Webflow determines user engagement and is affected by the ease of use and degree of navigation of the Web applications user interface[11]. A Web application aiming at achieving Webflow should posses a high degree of user interaction, since it can improve its ease of use and navigational quality [5]. It is possible to verify all these features by carrying out user interaction inspections, in which expert evaluators,or even the development team, can examine design, navigational and ease of use related aspects of a user interface[14]. In order to assist software engineers in identifying navigationaland ease of use problems early in the Web application development process, we proposed a set of usability inspection technologies for low fidelity prototypes (or mockups), which are images that show how the software would look like after its implementation [17]. These technologies are the Web Design Usability Evaluation (Web DUE) technique [16] and the Mockup Design Usability Evaluation (Mockup DUE) tool [15], which guide and assist inspectors in the identification of user interaction problems affecting user experience and engagement. Also, to facilitate identifying navigational problems, the Mockup DUE tool allows linking the mockups prior to the inspection so that their navigation can be simulated during the inspection. We have evaluated the DUE technologies through empirical studies to verify their feasibility [15]. The results from the studies showed that using the technique allowed finding more user interaction problems in less time, when compared to techniques that are used later in the development process [16].