*2.4.1. Tacit knowledge*

Tacit knowledge can cause critical knowledge, goals, expectations or assumptions to remain hidden. In consequence, the emergent requirements will appear incomplete and inappropriate, which can cause poor systems or costly effects [18].

### *2.4.2. Situatedness*

Situated actions involve a dynamic interaction with the actor and its environment; they only acquire meaning through interpretation in a specific context [19]. Situated actions involve conscious reference to the context and choice of action. An action is not situated if it takes the form of a prescribed response or if it is an unconscious automatic response. In ISD, situated actions occur frequently; in consequence, requirements are mostly situated and depend on a process of negotiation. In this situation, domain knowledge is fundamental in order to understand the rationality behind requirements, facilitate the negotiation process and propose technological aspects of the solution according to the real necessities of the domain specialists.

### *2.4.3. Disperse knowledge*

Products or solutions in ISD are so complex that the human knowledge required to develop them generally is vastly larger than the maximum individual human capacities [20]. Therefore, organized teams formed of specialists must develop them. In order to cooperate in the solution, domain specialists must share some knowledge about the domain. However, they always have different backgrounds, perspectives, interests and expectations, and their knowledge and experience vary depending on their own practice and role in the domain. Sometimes even inconsistent and incompatible beliefs can exist. Product developers or solution-solvers should reconcile and prioritize the diverse beliefs and knowledge about the application domain in order to incorporate it to the solution.

### *2.4.4. Asymmetry of knowledge*

Domain knowledge is the knowledge of the area to which a set of theoretical concepts is applied. In ISD, the concept of domain knowledge has two meanings. Firstly, solution domain knowledge corresponds to methods, techniques and tools that form the basis for the development of the product or solution. Secondly, those products or solutions are developed to necessities of real-word problems that exist in an application domain. Thus, both solution domain knowledge and application domain knowledge are necessary to develop the product or solution [20].

Asymmetry of knowledge, or symmetry of the ignorance, refers to the knowledge gap that exists between domain specialists, owners of the application domain knowledge, and requirements engineers, owners of the solution domain knowledge [5]. In ISDs, this phenomenon is increased because of the large amount of tacit knowledge involved. When the gap is big, there is not cognitive empathy and the communication process is not effective. Therefore, requirements engineers could produce models that do not represent the reality.
