Spatial and Temporal Digital Libraries


	Now, we will cover the various ways in which users are allowed to perform searches in spatial and temporal DL.
	Keywords:
	This is a very fundamental search method that is present also in traditional digital libraries.
	Navigational classification hierarchy:
	This search method should also be familiar to most of us. Now, there’s a digital library system called Digital Library for Earth System Education (short form – DLESE) which employs this kind of search interface. DLESE had focused on providing shared geo-science materials to the educational community, to support teaching and learning about the Earth system. Users can search for materials primarily in 2 ways – using keywords and by navigating its classification hierarchy.
	This picture shows a portion of DLESE resources organized according to the subject. Alternatively, the user may choose to view resources organized by grade level or resource type. Now, let’s assume the user selects agricultural science. The user will then be able to view materials, or documents pertaining to argriculture.

	Timeline:
	Now, imagine the library has a collection of many volumes of historical text about the history of England, and you are doing a mini-project that requires you to give a summary of the major events in England in say… late 18^th century. If the digital library only provides a simple keyword search, you will have a hard time deciding which volume of text to go through and read. But what if the digital library goes 1 step further by first extracting dates from the text in the various volumes, and then plotted these dates against the volumes in which they appeared in? This should be very helpful in your search. Now, let’s see an example of a digital library system that does this.

	The Perseus project is a digital library of resources for the study of humanities.., and naturally, historical text documents form the major resource type. To handle the large volumes of textual data, methods were explored to automatically tag dates and place names in the documents. Dates were also plotted against the volumes in which they appeared. Let me show you an example. (show) In the figure, the vertical axis list the various text volumes. The horizontal axis shows the timeline. Now, let’s look at the dots in the figure. You can see that this particular volume (Russell) talks about history starting from around middle of 18^th century. Whereas this volume, Frank E. Smith, mainly focus on history nearing the end of the 18^th century. So, to satisfy your need of obtaining summary of the major events in the late 18^th century, you might want to have a look at this particular book. Actually, in Perseus, you can also click on the timeline to retrieve relevant sections of the text document.

	Informative map-interface:
	Just now we mentioned that Perseus plotted dates against the different volumes, so that at a glance, users can see the temporal shift across different volumes. We can imagine that this can similarly be done to place names. Places detected in text can be plotted on a map. Let’s me show you an example. (show) This map shows the various places detected in a particular volume. To be specific, this volume actually talks about London history. Notice the concentration of dots in England. (show) This is another example. Notice this time round, the concentration is on Northern America.

	Navigational map-interface:
	The last search interface we want to discuss is the navigational map interface. We’ve mentioned earlier that most resources such as aerial photographs, images, maps, historical text, etc. have geographical attributes. It was realized that instead of relying upon the traditional keyword search and hierarchical classification scheme for access to these resources, a novel and more effective approach would be to make use of a map-based interface. (show) By looking at the figure, you can have an idea on what we mean by navigational map interface. This picture is taken from the webpage of the Alexandria Digital Library (ADL). ADL’s collection focuses on information supporting Earth and Social Sciences, which includes resources such as aerial photographs, world maps, etc. In ADL, the main search interface will be this map browser. The primary function of this map browser is to let the user define spatial regions as one of the feature to search for resources. For example, in this figure, we’ve selected USA, which means we would only like to obtain resources which have some connection to America. Notice the square grids in the figure. This map browser allows us to go deeper inside the map, so that we can define a more specific geographic region.