Received 26 April 2016; accepted 24 July 2016; published 27 July 2016
Other things that may affect the users’ satisfaction in using the information retrieval systems are the way of information-displaying, and the simplicity of usage of the system.
The goal of this current paper is to depict the graphically relations between dissertations in order to provide effective subject-based, information retrieval within digital libraries. Keeping in mind that physical access to the underlying digital collection is not an option, efficient subject-based information retrieval is crucial for a successful digital library  .
A proof of concept is also provided in this study to demonstrate the applicability of the proposed research to current and yet-to-come visual, interactive, and subject-based, information retrieval systems within digital libraries  .
2. The Role of Information Visualization in Retrieval Process
Since the last two decades, several information specialists have paid attention to Human Computer Interaction (HCI) and the user interface design of information retrieval systems, as well as the digital libraries  .
The study of Daniel Hienert et al. showed that graphics and interaction techniques can be used intuitively and the questions can be answered very fast  . One important technique for designing such user-friendly interfaces is information visualization  .
Information visualization utilizes computer graphics and interaction to assist humans in solving problems  .
“Information retrieval visualization” refers to the information resources, the user questions, information retrieval model, the retrieval process and the retrieval results of invisible interior semantic relationship convert into graphics or images, and displayed in a two-dimensional, three-dimensional or multidimensional visual space, these intuitive image of spatial information to help users understand the search results, get the retrieval direction to guide the retrieval process, in order to progress the efficiency and performance of information retrieval  .
Retrieval process visualization can provide information feedback, allow the retrieval process reversible, support retrieval strategy control, and a user’s interaction  .
3. Information Retrieval Visualization within Digital Libraries
4. Proposed Approach
In academic libraries, Thesis’ sector is special importance, Quick retrieval possibility and awareness of subject relations between thesis and dissertations, is important for students, who want to choose a topic for their dissertation, as well as for researchers, who want to know the results of other researches on a particular topic.
5. Case Study
The proposed approach has been applied to the digital library of theses and dissertations in the Management and Medical Informatics Faculty of Tabriz University of Medical Sciences  . This IR system provides information via displaying subject relations between various titles of thesis. To design this system, we used the perforce visualization tool, and it is appropriate using by web browsers.
In Section 6 (comparative evaluation) we made a comparative assessment between an ordinary used system (MAKTUB) in the Tabriz University of Medical Sciences and our proposed system. The evaluation showed the major advantage of our designed IR system clearly.
6. Comparative Evaluation
In the current IR system of digital library of Tabriz University of Medical Sciences (MAKTUB) (Figure 1) users are able to search in all the libraries of the university or do in a particular college-library.
By typing the keyword (evaluation) in the search box, Results are provided as a list of resources includes the undergraduate, master’s and doctoral theses, that the term “evaluation” presents in the part of their bibliographic information. User can find bibliographic details by choosing one of the titles.
Due to lack of subject headings and the lack of Controlled vocabulary in resource indexing, search results for two words (“evaluation” & “assessment”) retrieves different results. And the search results are not subject-based. Furthermore in this system subject relations between these are not visible to users.1
6.1. In Proposed Visual IR System
In our visual information retrieval system, the disadvantages of the mentioned system have been fixed. The user chooses Management and Medical Informatics Faculty at first. On the first page of software, topics and subjects of all theses and their subject-based correlations will be showed graphically. The information is presented in two separated languages, English and Persian. The user can choose his/her arbitrary language and continue searching.
As typing a word, the system begins to search letter by letter and eliminates the unmatched results and achieves the most relative results finally (see Figures 2-4).
Figure 1. Tabriz university of medical sciences digital library.
Figure 2. Select health care management department.
Figure 3. The information presented in English languages.
Figure 4. The system begins to search letter by letter and eliminates the unmatched results (In English).
7. Discussion of Retrieval Information in Proposed Visual IR System
Issues devoted to thesis have controlled by using the subject headings.
The subject headings used to show the relationship between theses to assign the precise subject matter of the thesis.
Figure 6. Results have retrieved for “evaluation”.
Figure 7. Results have retrieved for “assessment”.
Providing graphical information, possibility of user interaction with the system and displaying the subject relations between the thesis using a graph, has caused to easily diagnose the subject relations with the user, so that the user can assemble information to meet all his/her needs about special subjects.
8. Conclusion, Future Work
In this article, an effort is to graphically exploit the relations between dissertations to provide more effective subject-based, information retrieval within digital libraries. Keeping in mind that physical access to the underlying digital collection is not an option, well-organized subject-based information retrieval is crucial for the effectiveness of digital library.
The proposed methodology could be applied to other information resources within digital libraries, thus providing a universal tool for user-centered, interactive, subject-based information retrieval.
During the process, users enhance their cognitive learning, since they are able to discover which subject headings correspond to their information needs.
Future work is oriented towards the exploration of other semantically rich information structures produced by librarians. The ultimate goal of this research is to contribute to the development of next-generation digital libraries capable of exploiting the wealth of knowledge accumulated within traditional libraries   .
1In the present application (MAKTUB), the dissertations information is only in Persian, and English language search is not possible, so the search operation has not been show by pictures.