Purpose: The present paper aims at identifying and extracting the dimensions, components, and criteria of digital library evaluation based on experts` opinions and the 5S conceptual framework of Goncalves.Methodology: This was an applied, documentary, and survey research making the best use of the fuzzy Delphi method (to extract criteria and develop the conceptual model), forming a trinity in methodology. To refine the components, and criteria, 20 Iranian and foreign experts were polled about digital libraries in 3 stages. The results of each stage were refined based on Minkowski formula. This was an applied research since it presented the evaluation criteria of Iranian digital libraries, and its results can be practically used, enabling digital libraries to evaluate and examine their status quo, and accordingly plan and enhance their activities. It was a descriptive study based on the research design and data collection method. To gather the data, three methods were used: documentary study, fuzzy Delphi (to extract criteria and develop the conceptual model), and survey, creating a trinity in methodology. Findings: During the three stages of the experts` poll, in Stream component 4 criteria, Structure component 4, Space component 4, Scenario component 5 and in societies component 3 ones were refined and also the results of each stage were refined using the formulas of Cheng and Lin model and ultimately the experts agreed with each other on 20 criteria.
Conclusion: A digital library evaluation model was designed with 5 dimensions (components), 20 criteria, and 50 sub-criteria. It was offered to all organizations and universities as an evaluation model for digital library performance examination, so that they properly perceive the efficiency and effectiveness of digital libraries and their services.