## 2 Literature Review and the Research Question  
Searching behaviors can be discussed at two levels based on their units of analysis: search tactics and search strategies. Previous research on these two levels of search behaviors is reviewed here. Search tactics have been important topic in information searching because they are essential and fundamental components of the search process. Since researchers have used tactics and moves interchangeably, the authors also include related studies on moves in the literature review. In an early study, [PERSON] [1] identified a set of 29 information tactics, and classified these 29 tactics into monitoring, file structure, search formulation, and term tactics. Most researchers have focused on query formulation and reformulation in analyzing search tactics. [PERSON] [8] differentiated the operational and conceptual moves that either keep or change the meaning of a query in the query reformulation process. While operational moves are characterized by reducing or enlarging the size of search results, conceptual moves are exemplified by intersecting, narrowing, or expanding the meaning of queries. [PERSON] and [PERSON] [13] identified cognitive moves in which users perform some kind of conceptual analysis of terms or documents and physical moves that are associated with the use of system features. [PERSON] and [PERSON]'s [14] knowledge-based tactics are associated with query reformulation, in particular, topic refinement. [PERSON], [PERSON], and [PERSON] [2] also identified query search-related tactics, such as searching for an author, terms checks, _etc._  
A series of search tactics constitute search strategies, which are a complex number of tactics that involve both information domains and modes of seeking [15]. [PERSON] and [PERSON]'s [11] work is one of the initial findings of search strategies named as building-block, pearl-growing, successive-reactions, most-specific first, and lowest postings-facet first, which are the most frequently cited strategies in the field. [PERSON] and [PERSON] [16] identified one of the frequently used strategies as \"interactive scanning\" that highlighted user interactions with systems. Also they addressed the usefulness of the strategy when a user is not familiar with the topic and needs high recall. Focusing on cognitive aspects of search strategies, [PERSON] and [PERSON] [17] identified five types of strategies: the known-item instantiation strategy, the search-option heuristic strategy, the thesaurus-browsing search, the screens-browsing strategy, and trial-and-error strategy. [PERSON] [18] summarized search strategies into two essential levels of categories: analytic and browsing strategies. Analytic strategies indicate goal-oriented and systematic, while browsing strategies are more informal and interactive. Another type of search strategy is in relation to feedback, and [PERSON] and [PERSON] [19] suggested five types of interactive feedback in relation to interactive IR. After the emergence of the internet, researchers began to find new types of search strategies in the web-based information environment. [PERSON] and [PERSON]'s [7] problem-solving strategies reflect the hyperlink and search function characteristics of the web environment including various strategies, such as surveying, double-checking, exploring, link-flowing, back-and-forward-going, shortcut-seeking, engine-using, loyal-engine-using, engine-seeking, and meta-searching. [PERSON] [20] investigated the differences of search strategies applied by non-domain experts and domain experts. Based on a survey of 234 web users, [PERSON], [PERSON], and [PERSON] [4] found frequently used key strategies, such as opening multiple tabs and information re-access strategy. [PERSON] [6,21] identified 12 cognitive search strategies that include safe player, parallel player, link dependent, to-the-point, known address, sequential player, deductive reasoning, and secondary search. Search strategies were also generated from search log data.