**4. Explicit versus implicit interaction**

In the customary computing models, users are expected to interact with the system (engineered product) explicitly—hence explicit HCI (e-HCI). In the case of e-HCI, the interaction design aims to design and present the engineer product in such a way users know the presence of the product, and they should learn and understand how to interact with the product. Hence, it is required to design the computer-to-the-user.

However, as the result of smart computing models like ubiquitous computing, where the interaction is desired to be implicit, the notion of the command and feedback design might requires to designing the user-to-the-computer as well so as to enable the computer perceive the context of the user [22]—leading to implicit HCI (i-HCI) [6].

Weiser's vision of ubiquitous computing, which demands that computer to be an invisible servant [23, 24], can be realized if the user interacts with the engineered product less obtrusively. This is also pertinent in designing smart devices that improve the efficiency and automation of industrial devices.

Also, with regard to HCI, invisibility of computers can be achieved, partly through i-HCI [22] and context-aware systems. On the other hand, in addition to providing natural interaction (such as speech and gesture), the e-HCI development for interactive ubiquitous systems requires consideration of capabilities and constraints of heterogeneous platforms and users. Hence, the designers and developers are often compelled to configure and integrate heterogeneous platforms to meet needs of ubiquitous computing, such as mobility and implicit interaction. Therefore, both considerations of designing the-user-to-computer and the computer-to-the-user might be required.

In interactive systems where the user interacts with the engineered product explicitly, the user needs to have the model of the system. Thus, the interaction design focuses on crafting the computer/device, assuming the user will understand the presence of the engineered product, and it can operate it with its motor capability. Thus, the focus is more about the human-to-computer (H2C) interaction.

For example, consider a user who conducts quality inspection in a manufacturing process while the item is being manufactured, the item might need to pass over a conveyor belt. The user (inspector) needs a control over the conveyor—from turning on/off the conveyor to speed control. Thus, the user needs to explicitly access the control panel. In such case, the important usability consideration for the interaction design is positioning the control panel using the right metaphors for the interface. Otherwise, the user would have the knowledge on the existence of the control panel and the associated buttons/switches. Yet the design of the control panel shall consider various usability attributes discussed in Section 2.

Alternatively, the interaction could be computer-to-human. For example (considering the example in the preceding paragraph), instead of requiring the user to directly manipulate the control panel, the conveyor could be designed to be smart and know the absence/presence of the user (inspector) might take actions autonomously or advise the user on favorable actions. This approach makes the interaction implicit.

In i-HCI, the presence of the user in the computing model is not primarily to interact with the product. But, the presence can be sensed by the computer, and the computer shall take actions (give feedback to the user) based on previously or dynamically modeled user's context. Implicit interaction is based on the assumption that the engineered product, with which the user interacts, has a certain understanding of users' behavior and action in a given situations being a user-aware [6]. Thus, the design and architecture of the engineered product need to consider

additional components (such as sensors and actuators) other than the components useful to attain the functional operations.

## **5. Conclusion**

Any engineered product is designed and constructed with the intention of solving user's problem, often, through improvement of the user performance and capacity. And the users need to interact with the product in order to utilize it for accessing the service/s or functionality/functionalities provided by the respective product.

The interaction between the user and the product is primarily for addressing the user's problem which is associated with the usefulness of the engineered product. But the usefulness of the product is only one aspect. Otherwise, the acceptability of the product is associated with the usability and usedness of the product as well. Therefore, considering computer/device as an engineered product, the design and architecture of any engineered product shall give due consideration for the design of human-computer/device interaction.

First and foremost, as a user is one who operates and interacts with engineered product; it is important to properly profile the user considering the user's motor capability, psychological makeup, as well as the perceptual and cognitive model. Secondly, as the engineered product, which eventually interacts with the user, would be constructed over a certain platform and set of technologies, it is worth to consider the capabilities and constraints of the platform over which the product is designed or the product itself. Therefore, the understanding of the user as well as the platform capabilities and constraints would help to consider the right types of interaction modalities.

Also, in the design and architecture of an engineered product, in today's technology and with the emerging needs of smart computing, interaction design might lead to the design of implicit interaction between the product and the user. This, in turn, requires integration of various technologies such as RFID, sensors, and actuators to build smartness in the engineered product. Hence, the design and architecture of engineered product need to take into account the specification and organization of additional components beyond the ones used for processing the functional requirements and storing the information produced in relation to the task.

#### **Author details**

Dagmawi Lemma Gobena Addis Ababa University, Ethiopia

\*Address all correspondence to: dagmawi.lemma@aau.edu.et

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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