human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "investigating exploratory search activities based on the stratagem level in digital libraries"
  Abstract: In this paper, we present the results of a user study on exploratory search activities in a social science digital library. We conducted a user study with 32 participants with a social sciences background—16 postdoctoral researchers and 16 students—who were asked to solve a task on searching related work to a given topic. The exploratory search task was performed in a 10-min time slot. The use of certain search activities is measured and compared to gaze data recorded with an eye tracking device. We use a novel tree graph representation to visualise the users’ search patterns and introduce a way to combine multiple search session trees. The tree graph representation is capable of creating one single tree for multiple users and identifying common search patterns. In addition, the information behaviour of students and postdoctoral researchers is being compared. The results show that search activities on the stratagem level are frequently utilised by both user groups. The most heavily used search activities were keyword search, followed by browsing through references and citations, and author searching. The eye tracking results showed an intense examination of documents metadata, especially on the level of citations and references. When comparing the group of students and postdoctoral researchers, we found significant differences regarding gaze data on the area of the journal name of the seed document. In general, we found a tendency of the postdoctoral researchers to examine the metadata records more intensively with regard to dwell time and the number of fixations. By creating combined session trees and deriving subtrees from those, we were able to identify common patterns like economic (explorative) and exhaustive (navigational) behaviour. Our results show that participants utilised multiple search strategies starting from the seed document, which means that they examined different paths to find related publications.

Connected through hyperedge HE-1 (induced by source paper "reading protocol understanding what has been read in interactive information retrieval tasks"):
  with members:
    - "the role of the task topic in web search of different task types"

Connected through hyperedge HE-2 (induced by source paper "analysis of search stratagem utilisation"):
  with members:
    - "contextualised browsing in a digital library s living lab"
    - "analysis of footnote chasing and citation searching in an academic search engine"
    - "a complete year of user retrieval sessions in a social sciences academic search engine"
    - "a usefulness based approach for measuring the local and global effect of iir services"
    - "extending search facilities via bibliometric enhanced stratagems"
    - "scientometrics and information retrieval weak links revitalized"
    - "science models as value added services for scholarly information systems"

Connected through hyperedge HE-3 (induced by source paper "contextualised browsing in a digital library s living lab"):
  with members:
    - "data requirements for evaluation of personalization of information retrieval a position paper"
    - "a complete year of user retrieval sessions in a social sciences academic search engine"
    - "a usefulness based approach for measuring the local and global effect of iir services"
    - "extending search facilities via bibliometric enhanced stratagems"
    - "cross concordances terminology mapping and its effectiveness for information retrieval"

Connected through hyperedge HE-4 (induced by source paper "a complete year of user retrieval sessions in a social sciences academic search engine"):
  with members:
    - "a usefulness based approach for measuring the local and global effect of iir services"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.DL(Digital Libraries)