The DGSD is a genre of database known as a digital gazetteer. The term gazetteer generates some confusion in Chinese studies, since it is the English word most commonly used to describe the Chinese local geographies known as 地方志difangzhi. As the expression is used by geographers, a gazetteer refers to a place name directory, like the list at the back of an atlas. In a networked computing environment, gazetteers refer to databases organized around named places and their locations, and they have become an essential to all spatial search infrastructure. A gazetteer is distinct from a geographic information system (GIS), although the two are often used together and frequently translated into one another. A gazetteer is a database about named places, while a GIS is a system for storing, analyzing and displaying georeferenced information. In a GIS about land cover or public health, for instance, data organized by spatially located named places might play a relatively limited role.
By contrast, spatial information for historical scholarship is most commonly derived from texts. Unlike data digitized from maps or observed from sensors, land surveys, or satellites, texts are saturated with place names. The critical task for historical geography is to determine how those names relate to entities that can be mapped, when those entities existed, what attributes are essential to understanding and classifying them, and how this information changed over time. Historical GIS systems like the Vision of Britain/Great Britain Historical GIS (GBHGIS) and the China Historical GIS (CHGIS) are therefore all designed around gazetteer architecture.
A gazetteer can be used to answer research questions about historical political geography per se. It can also be utilized as one component of a data architecture. For instance, future users of the DGSD can integrate new data sources for research and visualization on the geography of social networks, commerce, transportation, artistic practice, or any other topic that would benefit from spatially explicit treatment.
The Digital Gazetteer data model is highly indebted to the one developed by CHGIS, though it has been extended to accommodate the additional attribute information available from the Alphabetical List. Each Alphabetical List headword was initially designated as an entity. This entity indexes the multiple names, ranks, attributes, parent-child relations, and change events associated with a particular place. Since Song places experienced frequent changes in name, parent-child relations and other characteristics, the information about each entity is located in two related tables, each indexed to the entity table.
With some data processing, the DGSD can be used to recreate Hope Wright’s original entry style, allowing users to browse the database as if it were simply an electronic version of her text. However, using a full range of SQL queries and spatial analysis, it can also be used to create maps and snapshots depicting the political landscape during a given period or to analyze the frequency of changes and their characteristics.