## 2 Related Work  
This paper focuses on two main areas of interest: requirements engineering [16; 18; 19; 20; 21; 22] and scope (or effort) estimation [23; 24; 25; 26; 27]. In the context of Agile project scope estimation, two important aspects are examined in more detail, early-phase requirements elicitation and scope estimation based on these early requirements, as well as the benefits of the introduction of the modeling paradigm in both [19; 21; 22]. While the Agile methodology offers a flexible development approach with a focus on individuals, collaboration, working software, and rapid responses to changes [12], the process of requirements elicitation begins with the project concept clarification [28]. This step involves identifying project stakeholders [29] and establishing goals, and also using various techniques, such as interviews, focus groups, brainstorming, and workshops, to gather initial requirements [12; 28]. During requirements elicitation, the aspects of risks identification [10; 11], stakeholder communication, and human resources management [9; 29] should also be considered. Proposals for Agile requirements elicitation exist, outlining the need for tailored approaches [1; 16; 18; 19], but only a few of them mention early-phase requirements elicitation. Agile may not always accommodate different representations, though textual notation may not always be an appropriate tool for describing different artifacts, like data models, user flows, or the user interface [2; 12]. Just as in classic requirements engineering, in Agile, challenges concerning miscommunication might still occur. To address the challenges of representing artifacts that are not easily conveyed through user stories, solutions exist proposing to incorporate modeling with Agile practices [19; 21; 22]. Strategies for the elicitation and management of requirement [2; 12; 18] must be considered in the context of early scope estimation, as it relies on a backlog or a requirements list, which needs to be developed rapidly and employed to accurately measure scope. Therefore, we analyze in more detail the approaches that introduce requirement elicitation and management strategies [18; 19; 22], and the modeling for structuring the requirement elicitation processes in Agile projects [19; 22]. A framework for improved software requirements elicitation in SCRUM [18] covers three elicitation phases. In the pre-elicitation phase, it utilizes a joint requirements document for identifying, breaking down, and prioritizing requirements based on stakeholder feedback. During mid-elicitation, an initial scope document and priority list of a high-level requirements are used to further decompose and refine requirements using mind mapping techniques. This process involves breaking down each requirement into as many branches as possible for both functional and non-functional aspects, ultimately resulting in the creation of user stories. The post-elicitation phase is performed during development for finalizing and validating user stories derived from mind maps. These user stories are included into the product backlog, where the stories are corrected and refined by the product owner and the development team for inclusion in the sprint backlog. This framework outlines that the hybrid of different approaches and the involvement of multiple stakeholders improves Agile software requirements. Another method for the elicitation, documentation, and validation of requirements (MEDoV) [19] is tailored for Agile and Lean software development. The method supports decision-making processes, and during its first phase, business objectives and KPIs are identified. It employs UML Use case, Class, and Activity diagrams for requirement modeling. The developed \"to be\" and \"as is\" models can also be used for communication and validation purposes, thus increasing the clarity of requirements with minimal impact on agility. An MBSE approach to Agile [22] utilizes both the SCRUM and the model-based system architecture to leverage the benefits of both methods.