Consumers and users of a system ask themselves 3 major questions before deciding on a system; • Will it function properly?• Can the users use it successfully?• Will the users find it suitable for its purpose?These questions suggest a paradigm that users are dependent on the system fulfilling criteria such as utility, usability, likeability, acceptability and cost. A successful system design in terms usability requires a fulcrum to provide balance with functionality. With growing demands, computers are becoming more powerful and cheaper at the same time and usability factor plays a more and more crucial role in driving the decision to whether accept a system design (Shackel and Richardson, 2008). Thus, to achieve good system design, usability is an essential goal and is the dynamic integration of 4 dynamic factors; user, task, tool and environment (Bennet, 1972). Based on this framework criteria, technically usability factor is further dependent on the design of the tool and the amount and effectiveness of the user support provided. Usability is the ease of use and measure of efficacy (Miller, 1971). This theoretical definition is satisfactory, conceptually. But, the in terms of quantifiable properties, many types of usability goals were defined which will be discussed further in the next chapter. Figure 1 A model of the attributes of system acceptability.2.0 TYPES OF USABILITY GOALS 2.1 LEARNABILITYLearnability means exactly what it says. It is the answer to the question; how easy is it for the users to complete basic tasks successfully at the first attempt? It is one of the, most necessary characteristic of the usability factor as the best impression is the best impression. When a user encounters the user for the first time, there is a necessity for the system to be easy to understand to build interests and flourish creative ideas. Unquestionably, there are systems that are designed that gives its users a tough time to learn and can afford to provide sufficient training guides. However, conventionally this affects the likeability factor of the tool-user interaction. So, to say, each system’s learnability can be described with a standard learning curve that increases positively with time. Systems designed for interactive information kiosks that are made for malls, libraries, museums and likewise are excluded as these systems are designed for a walk-up-and-use system. In other words, users must be successful at their first attempts. Also, systems that are upgrades of a previously published system are not susceptible to standard learning curves as well because users would have acquired fair-bit of knowledge in using the system (Telles, 1990).2.2 MEMORABILITYMemorability is an attribute of the usability factor that is related to the ability of the user to have sufficient knowledge of the system from the previous experience; memory from previous encounter. Basically, an answer to the question of how easy is it for the users to re-establish proficiency when they return to using the system after a significant amount of time? These users are the 3rd major category of users after the novice and expert users; so, called casual users. These users use a system irregularly, so for every time they use the system, they do not start from the beginning, they just must recall how it was used before. Extensively, the ability to remember the interface is often improved by steeper learning curves of learnability. For instance, many signs that are seen at places are never significant enough to remember up until the meaning of the sign is understood. In other words, the sign is easier to remember. However, as far as the measurability of this attribute goes, memorability is close to the ability of the user to remember and execute. Two memorability assessment methods are memory test on individual after using the system and alternatively, a standard user test on casual users that tests on the amount of time taken to perform basic tasks after having left the system for specified significant amount of time (Wilson, 2010).2.3 ERRORSErrors account to the question of the quantity of errors, a user makes, severity of the error and the ease of recovery from the error been made. Few errors, possibly, non-catastrophic ones are highly plausible in any user’s encounter with a system. Nature of errors are extremely important to measure this attribute in regards of usability. Errors originated from an incorrect action of the user could cost an extended task completion time provided that the errors can be corrected immediately. Error rates, however, are measured by counting the number of misguided or deviated actions taken that slows down completion period of a specified task. On the other hand, catastrophic errors which by nature, solely is rooted from factors like the absence of familiarity with the mistaken part of the system which extends faulty of accomplished product. Catastrophic errors are of different nature and requires specialized effort in attempts of recovery to avoid risk in damaging product accomplished.?2.4 EFFICIENCYEfficiency is the measure of how quickly users can accomplish tasks after they are familiar or proficient with the design of the system. It is highly relatable to the learning curve explained in the learnability attribute. Efficiency is well-reflected on the expert user’s steady performance learning curve. Over time, the line flattens as the user’s proficiency and efficiency becomes prominently maximum of one’s ability to learn. Measure of efficiency is common for experienced users. Users are defined to be experienced considering the time spent on the system. More conventionally, from the learning curve, when the user no longer shows significant improvement on the period spent on completing basic tasks, that ‘experienced user’ has reached maximum efficiency of their own ability, thus the time recorded represents the quantifiable measure of efficiency.2.5 SUBJECTIVE SATISFACTION Regarding the usability framework criteria, user being one humane entity that highly affects all the diverse types of usability, undoubtedly, plays a more crucial role in determining the unique satisfaction level of users. Satisfaction level differs from one user to the other; hence, exposing a subjective nature. Each user, can be asked, how pleasant is it to use the system. As subjective as the question may result in, it is alternatively, a highly appropriate approach to measure the satisfaction level of the users. Traditionally, in efforts of making sure the measurement is indeed consistent, users are questioned after having used the system. To ease the process, the pleasantness of the system is often being scaled in magnitude of agreement to subject matter. Consequently, making the response easier to analyze as they are can be statistically analyzed and mathematically represented.?3.0 DESIGN PRINCIPLES Design principles are sets of commonly appropriate regulations, guidelines, human biases, and design considerations, that reflect the acquired knowledge and experience of users and designers. They facilitate the birth of innovative ideas of a system. Design principles usually consolidate improvements across all design-related disciplines, including behavioral science, sociology, physics, and ergonomics.Design principles are intended to facilitate designers to determine the appropriate approach to enhance usability, influence perception, increase appeal, teach users, and make sound design decisions during projects. These principles can ensure the success of the system from all aspects. The way in which the designer can apply each principle also subjective to his or her ability to rationalize and figure out the problems waiting to be solved (Ghaoui, 2006).3.1 PRINCIPLES BY DONALD NORMAN Norman describes 6 major design principles (Norman, 1988). Despite the age of the book, its content has proven its relevance to up to date internet standards by providing core ideas that are versatile and independent of time. In fact, the design principles are highly appraised as technology advancements continue to progress; yielding desired consumer-friendly interfaces of systems.These attributes of the six basic principles generally focus on features that make the user experience as smooth, easy and as pleasant as possible. Norman describes six fundamental principles: visibility, feedback, constraints, mapping, consistency, and affordances. Designers have extensively used these basic principles of design to create engaging work that clearly communicates to the users.?3.1.1 VISIBILITY Visibility discusses on making relevant parts of the design in a system literally and figuratively, visible. Essential elements to the design can be highlighted with increased visibility and minor elements that are considered secondary or tertiary can be subjected to less visibility. The hierarchy of the design can be depicted in order of the magnitude of the function to match its criticality along with the visibility of that part of the system. Thru this approach, contents will be prioritized according to importance and functionality. The emphasis on key element will defend the importance and promise no compromise towards its purpose. So, basically emphasis on core elements of the system should always be in the mind of a designer and must their high visibility. For example, an elevator that will only operate after an access card is inserted, must make sure that the card reader ‘prompts’ the user to insert the card before the user misguidedly, attempts to operate the elevator without inserting the access card. Thus, efforts to make it more visible must be taken. Either by making the card reader more obvious, provide an auditory message, or label on the card reader that gives out light.3.1.2 FEEDBACKFeedback is about information conveyed in return to what has been accomplished. An assurance to an action that has been done. Indication to user that their action is either wrong or right, if right, then the next step’s guide. This principle is highly related to the subjective satisfaction of users as feedback is a serious approach to avoid frustration and discomfort for users in executing a task. For example, after the enter button has been hit on the Google search engine, a loading circle appears indicating the search is being processed. Without the loading circle in motion, user will not be able to identify if their action has been accepted or has a reaction. Hence, this principle ensures the smoothness of user’s execution flow. ?3.1.3 AFFORDANCEAffordance is defined as a reference to the perceived and the actual properties of an element of the system, in this context. Generally, a relationship between what something looks like and how it is used. Regarding the human-computer interaction, interfaces must be user-friendly to afford to present users with intuitive information that can be accessed easily. For example, the designer of a website need to be able to present users with elements with intuitive information that can be figured out easily. If the designer fails to consider affordance, worst case scenario, users will immediately leave the website as they are not able to find the information they are looking for.3.1.4 MAPPING Mapping is the interaction between control and effect. Conceptually a superior design will be able to depict the effect of what the controls affect. Controls include the users’ interaction with the website. Just like the feedback attribute, only, mapping provides information to the user based on their control of the system. For example, quite conveniently, the vertical scroll bar that enables user to scroll to the desired area and he control, and the effect is executed and affected at the same time, respectively. This is because the scroll bar not only shows where you are going, but also shows your position. As the scroll bar is dragged down, the page will also be dragged down, perfectly reflects a closely mapped, control and effect. 3.1.5 CONSTRAINTS Constraints imposes limitations to interactions within the interface. This constraint can often be something that was inevitable to the design. For example, the size of a phone’s screen. The screen size limits the size of the display. This limitation forces user to take additional actions to overcome it. In this case, a single page website must be scrolled down to seen fully. 3.1.6 CONSISTENCY Consistency refers to uniformity throughout the system. It refers to the ability of the system to have consistent results to consistent inputs. The same action must cause the same reaction throughout the system, regardless of any aspect. For example, logos of brands. These icons that are used consistently throughout the system will prove to have a significant association of the subject matter, hence making it more memorable. Another good example is controls that have the same effect throughout the system. Consistent functionality reflects uniformity in system design.3.2 PRINCIPLES BY JAKOB NIELSENSNielsen published his 10 most general principles of design principles for interaction design, that are more famously known as heuristics as to reflect the nature of the 10 principles to be more like rules of thumb than guidelines. A heuristic evaluation is a usability inspection process for computer software that assists to recognize usability difficulties in the user interface (UI) design. It particularly concerns evaluators observing the interface and assessing its compliance with recognized usability principles (the “heuristics”).?3.2.1 VISIBILITY OF SYSTEM STATUSThe system should always make sure to inform users about what is happening, through relevant feedback within justifiable amount of time.3.2.2 MATCH BETWEEN SYSTEM AND THE REAL WORLDThe system should be able to converse the users’ language, with commonly used terms and phrases that are accustomed to the user, rather than system-oriented terms. So, to say, mimic real-world conventions, delivering information seem in a natural and logical order. Figure 4 Using real life metaphor in computer application.3.2.3 USER CONTROL AND FREEDOMVery frequently, users have grown accustomed to choosing to escape uncomfortable system as mistakes or faults begin to unravel. Users need an escape route to undo and redo their actions as desired. Support dialogues that acquire user’s confirmation are highly recommended to prevent further mistakes from happening.3.2.4 CONSISTENCY AND STANDARDS Users must be able to use similar conventions throughout the system as that reflects uniformity in the system. This also avoids user errors. 3.2.5 ERROR PREVENTION Rather than providing error alerts and support dialogues in recovery efforts, a superior design should be able to defend its system from plausible problems closely precedented to avoid catastrophic and unexpected blunders.?3.2.6 RECOGNITION RATHER THAN RECALL Increase the visibility of prominent elimination and prioritize in accordance with importance and functionality. A user should not be expected to remember unnecessary details of the system. Help and support should be extensively provided wherever and whenever in need. ?3.2.7 FLEXIBILITY AND EFFICIENCY OF USE For added efficiency, speed increasing function elements should be included in the design, such that the system will be able to accommodate both, expert and novice users. Users should be able to have ‘shortcuts’ to frequent actions, to cut down on time taken to accomplish a basic task. Figure 8 Appropriate shortcuts3.2.8 AESTHETIC AND MINIMALIST DESIGN Dialogues should be concise and precisely to the point. irrelevant information should be omitted so that it doesn’t overshadow important information’s visibility.?3.2.9 HELP USERS RECOGNISE, DIAGNOSE, AND RECOVER FROM ERRORS Support dialogues intended to solve errors should be concise and precise in simple terms, adequately explaining the situation and propose constructive solution options. 3.2.10 HELP AND DOCUMENTATION Although documentation is not favored by designers, it is an important documentation of the product a consumer is purchasing. thus, documentation can be made simple by listing out guided steps and small portions. Information provided in the documentation should also be easy to obtain.