The objective of this research project is to aggregate the preferences of different stakeholders using argumentation in a Negotiation Phase. This is done in the context of a specific project, which is explained in this thesis. The aggregation of several stakeholders' preferences may incur into different conflicts due to differences in the needs of each stakeholder. This is where argumentation can be used in order to solve conflicts, as new information may appear and lead to changes in the preferences, even adding new preferences or removing old ones. The concept of Negotiation Phase is introduced in order to allow stakeholders to review their preferences, discuss, argue, and enter new information. As a result of this phase, preferences may be changed in order to solve conflicts, or we may find out that a conflict is not solvable by argumentation, leading to other solutions such as splitting a scenario in order to manage different choices separately.