## 2 Proposed Benchmarking Method and Objectives of the Paper
* A _(user) need_ is an explicit expression of interest for a benefit to be enjoyed by means of using or owning a product or a system. * A _competing factor_ is a parameter through which a system can be evaluated, which features specific benefits and advantages for one or more stakeholders of the product under consideration; in other (scientific) contexts, a competing factor would be referred to as a \"metric\". * A _requirement_ is the combination of a competing factor and the corresponding performance level or the degree of fulfilment (either qualitative or quantitative) a specific system has achieved. If interpreted in a design perspective, a so-defined requirement is a target to reach in order to comply with a design specification. * An _attribute_ is a property or a feature of a product or a system, which is ascribable to the attempt or necessity of bringing a specific benefit; new attributes are therefore proxies of the introduction of new competing factors in value curves. Given these definitions, the following conditions apply to enable an effective interpretation of value curves considering different competing technical systems. * Competing factors are defined in a way that is consistent with user needs and expectations, i.e., they are an expression of a benefit, e.g., \"cheapness\" instead of \"cost\". This means that, with reference to Figure 1, the system 1 outperforms the system N for the first competing factor, and, as such, it is preferable in terms of the benefit underlying the first competing factor. Still, the system 1, if compared to the system N, has been designed in a way that it has fulfilled a more challenging requirement in the perspective of the first competing factors. * The competing factors presented in a value curves diagram are mutually independent, as they are intended to show how different systems have fulfilled requirements differently. Indeed, requirements are, in their turn, independent and non-redundant still according to the expected properties of design specifications [18; 44]. The present paper shows a case study in which values curves are built upon a structured search for information concerning a specific industrial domain, where the main target was the individuation of currently fulfilled requirements. A characterization of currently available products in terms of competitive factors and the determination of possible contradictions to be solved in subsequent design phases are inferred based on the value curves. Therefore, the lessons learnt concern the utility of using value curves as a graphical tool to deduce similarities and differences between competing technical systems, as well as their potential for individuating unfulfilled requirements that might feature future design endeavors. The structured search is organized as illustrated in Figure 2. The definition of the industrial domain of the study, in terms of the main functionalities of the technical systems under consideration has to provide, is presented in Section 3. The search method aimed at collecting relevant documents is presented in Section 4. The competing systems pertaining to the industrial domain of the study, their classification (in terms of their belonging to a family of solutions), and their main characteristics are shown in Section 5. In Section 6, the main competing factors that characterize these systems, i.e., the attributes that these systems and/or their subsystems should have, the benefits that they should provide, and the problems that they should solve (or actually cannot solve), are discussed based on the information available on patents and scientific papers. The identification of the performance level that characterizes each competing factor for each competing system is presented in Section 7. The creation of the value curves is presented in Section 8 along with implications for the technical systems under consideration. The rest of the article includes Section 9, where methodological remarks are made, and Section 10, where conclusions are drawn.