2.a Unique ID
A 6-digit unique numeric identifier for each historical instance.
2.b Entity ID
The numeric identifier of the entity associated with each historical instance.
2.c Feature Type
The type of administrative unit that described each entity during any period of its existence. The complete list of feature types is listed in Section 5 of this document.
2.d Change Types
We use the term historical instance to refer to each state of affairs that associated with any entity. An entity that was stable during the course of the dynasty has a single historical instance. Every additional historical instance represents a change of state with regard to that entity and has a date range and a type of change. The DGSD change-type categories, based on those defined in the China Historical GIS, are listed in Section 5 of this document.
Sometimes, a single complex historical change must be modeled using multiple change types, resulting in multiple historical instances associated with a particular date. For example, in 1005, entity 40260, Tanglin (唐林), was abolished, and its territory was merged into entity 20340, Guo, (崞). The DGSD records this as two events, resulting in two historical instances associated with Tanglin. One begins at the inception of the Song in 960 and ends in 1005 with the change-type Abolished. Another begins and ends in 1005 with the change-type Merged. Disaggregating the two components of the event makes it possible to conduct queries by change type. However, when performing queries and data analysis, it is important to remember that historical instances that relate to a particular entity and that have matching begin-dates or end-dates may represent multiple simultaneous components of a historical event that might best be reaggregated.
2.d.i Begin Change Type
The Begin Change Type field records events that initiated particular historical instances: the Begin Change Type field marks events that brought a state of being into effect. If a Begin Change Type date is identical to an End Change Type date, it also indicates that two changes were simultaneous. Establishment, Reestablishment, Regained and Split events are specific to the Begin Change Type field. In data processing it is often advisable to aggregate several types of events together as Establishment Events. Demotion or promotion events will appear as both the Begin Change Type of a new historical instance and the End Change Type of an old historical instance.
2.d.ii End Change Type
The End Change Type field records events that brought an end to particular historical instances. Changes that are specific to the End Change Type field are Abolishment, Reabolishment, Lost and Merged. As with Establishment Events, it is often advisable to aggregate these as Abolishment Events.
Even though MM-DD-YYYY accuracy is possible for some Song dynasty historical change events, the DGSD follows Hope Wright in tracking only years of events. All events are currently presumed to begin on January 1 of the year in question.
2.e.i Begin Date
The date of the Begin Change event.
2.e.ii End Date
The date of the End Change event.
2.f Target ID
When an entity was transferred, merged or split into one or more other entities, the target entity or entities appear in the Target ID field. The updated parent entity is listed in the requisite field—county for rank 4 entities or prefecture for rank 3 entities.
2.g Feature Type
The feature type of the selected entity during the time period is displayed as a numeric value.
An entity’s parent prefecture during a period defined by given begin and end dates, for entities of county rank or lower.
The parent circuit of a given entity.