## 9 Evaluation
### Methodology  
Overall, our evaluation methodology included focus groups, summative usability testing, the think-aloud protocol and the cognitive walkthrough method. Focus groups were used at the earlier stages in order to identify the usability requirements [35]. Led by experienced moderators, the focus groups sessions took place at the Hellenic Parliament, where the archivists and the end users collectively discussed their expectation of the functionality and content of the SARA application. The focus groups included few people at a time who discussed preservation methods and the types of semantic data required for retrieval of archived documents as a part of the design and the formative evaluation during the development iterations. Major findings included the need for metadata-driven semantic search, the use of the semantic information, such as entities, topics and opinions and provision of information that would help end users to better understand the content of the archived documents. The latter was exemplified as an overview of the semantic metadata, as well as links interconnecting metadata items. The main usability evaluation method that was used in the evaluation presented in this paper was the summative usability testing, that is the summative evaluation of the SARA interface. The summative evaluation is used at the end of the design and development life-cycle for finished user interfaces. In this evaluation methodology, real users perform concrete tasks that are designed to measure effectiveness, efficiency and satisfaction. The feedback from the users is evaluated against the usability requirements. The summative usability testing is performed in a controlled environment and aims to collect both subjective and objective feedback. The Likert scale is a commonly used representation for graded user feedback. The subjective feedback from the participants was collected using the complete online questionnaires using the Likert scale of 1 (very low) to 7 (very high). In our study, the think-aloud protocol was used to collect partial subjective feedback from the participants. The participants were encouraged by the facilitator to vocalize the rationale for their actions, as well as the intended interactions while they were performing the tasks of the usability testing. This enables deeper understanding of the user actions, providing insights in the user attitude. It complements with the user feedback in traditional questionnaire web forms and the interaction logs. In addition, the cognitive walkthrough method was used before the main evaluation sessions. Few experienced user interface evaluators and the designers interacted with the SARA interface looking for the best ways to perform certain tasks in search and retrieval. The aim was to identify potential shortcomings or issues and also help the evaluation facilitators verify the task-based scenarios that would be used for the evaluation. Discoverability and efficiency were major performance indicators for the SARA interface; however, the feedback from the users distinctly mentioned that the quality of the key semantic metadata of the web archives could be the most crucial content-specific reason for their acceptance. That statement was put to the test during the final evaluation and was particularly articulated by specific questions for the subjective feedback of the users at the end of each session. The importance of a metadata type (e.g., entity, event or topic) is the perceived usefulness of this type in the context of the user query. The quality is the direct qualitative aspect of the actual metadata values. For example, for topics the quality translates to easiness to understand, descriptiveness and logical connection to encompassed entities. Normally, the importance, quality and an overall acceptance of metadata are not affected by means of presentation as long as these means do not favor or hinder particular metadata types.