This chapter describes interfaces to support navigation (or browsing) as part of the search process. Chapter 3 discusses theoretical models of browsing versus search as information seeking strategies, as well as the notion of information scent and information architecture. As mentioned there, one way to distinguish searching versus browsing is to note that search queries tend to produce new, ad hoc collections of information that have not been gathered together before, whereas navigation/browsing refers to selecting links or categories that produce pre-defined groups of information items. Browsing activities can also include following a chain of links, switching from one view to another, in a sequence of scan and select operations. Browsing can also refer to the casual, mainly undirected exploration of navigation structures.

Navigation structures lend themselves more successfully to books, information collections, personal information, Web sites, and retrieval results than to vast collections such as the Web. Nonetheless, there have also been attempts to organize very large information collections such as the Web.

Category systems are the main tool for navigating information structures and organizing search results. A category system is a set of meaningful labels organized in such a way as to reflect the concepts relevant to a domain. A fixed category structure helps define the information space, organizing information into a familiar structure for those who know the field, and providing a novice with scaffolding to help begin to understand the domain. Category system structure in search interfaces is usually either flat, hierarchical, or faceted (this is discussed in detail below).

This chapter describes several areas that are gaining in importance and are likely to play a significant role in search interfaces in the future. These predictions come primarily from extrapolating out from emerging trends. The areas that seem most likely to be important, and so demand changes in search interface technology, are: mobile search, multimedia search, social search, and a hybrid of natural language and command-based queries in search. Each is discussed in detail below.

Mobile Search Interfaces

Mobile communication devices are becoming increasingly popular as information access tools. A recent survey of more than 1,000 technology leaders and other stakeholders said they expect that mobile devices will be the primary connection tool to the Internet for most people in the world in 2020 (Rainie 2008). They also predict that voice recognition and touch user interfaces will be more prevalent and accepted by 2020. Usable interfaces for search on mobile devices are only now beginning to emerge, but this area will most certainly undergo rapid development and innovation in the next few years.

Until recently, mobile devices had small screens, awkward text input devices, and relatively low bandwidth, which pose challenges for information-rich applications like search. However, bandwidth is increasing, and the recent appearance of personal digital assistants (PDAs) with relatively large, high-resolution screens, such as the Apple iPhone, are making search on mobile platforms feel more like desktop-based Web search.

Keeping the Interface Simple

The job of the search user interface is to aid users in the expression of their information needs, in the formulation of their queries, in the understanding of their search results, and in keeping track of the progress of their information seeking efforts.

However, the typical search interface today is of the form type keywords- in-entry-form, view-results-in-a-vertical-list. A comparison of a search results page from Google in 2007 to that of Infoseek in 1997 shows that they are nearly identical (see Figure 1.1). Why is the standard interface so simple? Some important reasons for the relative simplicity and unchanging nature of the standard Web search interface are:

• Search is a means towards some other end, rather than a goal in itself. When a person is looking for information, they are usually engaged in some larger task, and do not want their flow of thought interrupted by an intrusive interface.

• Related to the first point, search is a mentally intensive task. When a person reads text, they are focused on that task; it is not possible to read and to think about something else at the same time. Thus, the fewer distractions while reading, the more usable the interface.

• Since nearly everyone who uses the Web uses search, the interface design must be understandable and appealing to a wide variety of users of all ages, cultures and backgrounds, applied to an enormous variety of information needs.

The preceding chapters have discussed user interfaces to support search, with a focus on what is known to be successful (from a usability perspective) for the vast majority of searchers. This and the following chapter describe efforts to improve search interfaces by incorporating visual information into the display using techniques from the field of information visualization.

The human perceptual system is highly attuned to images, and visual representations can communicate some kinds of information more rapidly and effectively than text. For example, the familiar bar chart or line graph can be much more evocative of the underlying data than the corresponding table of numbers (Larkin and Simon 1987). The goal of information visualization is to translate abstract information into a visual form that provides new insight about that information. Visualization has been shown to be successful at providing insight about data for a wide range of tasks.

The field of information visualization is a vibrant one, with hundreds of innovative ideas burgeoning on the Web. However, applying visualization to textual information is quite challenging, especially when the goal is to improve search over text collections. As discussed in earlier chapters, search is a means towards some other end, rather than a goal in itself. When reading text, one is focused on that task; it is not possible to read and visually perceive something else at the same time. Furthermore, the nature of text makes it difficult to convert it to a visual analog. Most likely for these reasons, applications of visualization to general search have not been widely accepted to date, and few usability results are positive.

This chapter describes interfaces for the search results presentation portion of the information seeking process, focusing for the most part on ideas that are currently in use.

Document Surrogates

The most common way that search results are displayed is as a vertical list of information summarizing the retrieved documents. (These search results listings are often known as “search engine results pages,” or SERPs, in industry.) Typically, an item in the results list consists of the document's title and a set of important metadata, such as date, author, source (URL), and length of the article, along with a brief summary of a relevant portion of the document (see Figure 5.1). The representation for a document within a results listing is often called a search hit. This collection of information is sometimes referred to as the document surrogate. Marchionini and White (2008) note that document surrogates are summary information intended to help the user understand the primary object, as opposed to metadata more broadly construed, which can also serve this purpose but is often more tailored towards use by computer programs.

The quality of the document surrogate has a strong effect on the ability of the searcher to judge the relevance of the document. Even the most relevant document is unlikely to be selected if the title is uninformative or misleading. (Some Web search algorithms try to capture the quality of the title description as part of the ranking score.) The descriptiveness of the summary is also very important and is discussed in detail below.