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TGN: Frequently Asked Questions
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How many place names are in TGN?

Thousands of TGN place names are added and edited every year. As of May 2011, the TGN contained around 992,310 'records' and1,711,110 names.

 


Does the TGN have maps? Is TGN a GIS?
The TGN is not currently linked to maps, although the coordinates should allow you to find the places on a map. TGN is not a GIS. While many records in TGN include coordinates, these coordinates are approximate and are intended for reference ("finding purposes") only.


How much information is required to identify a place?
The logical focus of a record in the TGN is a place. The minimum record for each place includes a name, a place type, and a position in the hierarchy that shows its parent places (or broader contexts). The name alone does not identify a place because there may be many homographs. For example, there are 145 inhabited places called Springfield in the TGN, including the two below (from a Results List):

Example

Note that recording the state and nation alone would not identify the place; the county is required because a single state can include multiple "Springfields."


What are the relationships in the TGN?
The TGN includes equivalence, associative, and hierarchical relationships.

  1. Equivalence Relationship. All relationships between names within the same TGN record are equivalence relationships. In the example below, all names refer to the same city, Lisbon, Portugal.
     
    Example
     
    Among all the names that refer to the place, one is indicated as the preferred name, comparable to the descriptor in the AAT. This is the vernacular or local-language name most often found in scholarly or authoritative published sources (e.g., the name in bold in the example above). The preferred English name is also indicated. Institutions who wish to use TGN as an authority may use one of these two names to refer to the place consistently.

    Variant and alternate names in the record include names in other languages, names transliterated into the Roman alphabet by various methods, names in natural or inverted form (particularly for physical features, e.g., Etna, Mount), nicknames, official names, and historical names. Misspellings may be included if they are found in published sources.

  2. Hierarchical Relationship. The hierarchy in the TGN refers to the method of structuring and displaying the places within their broader contexts. Hierarchical relationships in TGN represent part/whole relationships and are typically indicated with indention, as in the example below.
     
    Example
     
    TGN is polyhierarchical, meaning that a place may have multiple parents or broader contexts. For example, the US state of Hawaii is administratively part of the United States in North America, but it is physically located in Oceania. One relationships is preferred; the non-preferred relationship is indicated with an [N] in the example below.
     
    Example
     
    Both physical features (including mountains and rivers) and political/administrative entities (including inhabited places and nations) make up the TGN hierarchy. Major subdivisions of the hierarchy typically include the continent, nation, first level subdivision, second level subdivision, inhabited place, and possibly neighborhood. Most nations have one level of administrative subdivision above inhabited place, and many have two levels. Generally, the hierarchy in the TGN goes only to the level of the inhabited place. However, the level of neighborhood has been included for some of the world's largest cities (as in the example below). Releases of the TGN will generally not include levels for streets or buildings within the boundaries of inhabited places.
     
    Example
     
  3. Associative Relationship. Associative relationships may exist between the records for places in TGN. For example, if an inhabited place has been physically moved (as when the location has been deemed unsafe due to flood or earthquake), there should be an associative relationship between the original settlement and the new settlement. In the example below, for the record for Ocotepeque, Honduras, the town was originally located to the NE of the current city, but was moved after the Marchala river flooded in 1935 and called Nueva Ocotepeque.
     
    Example

Are dates associated with places in TGN?
Dates for names or place types in TGN are expressed in notes called display dates, which are indexed by the two years that delimit the span of time indicated in the note. Dates may be known to different levels of specificity and varying shades of certainty. In the display date, uncertainty may be expressed. The note is then indexed using start and end dates that delimit the broadest span of time applicable. Since conventions used to describe approximate dates (e.g., circa) may vary depending upon context, this allows flexibility in establishing appropriate date spans for retrieval. Note that start and end dates are recorded in the database but are hidden from the end-user. The examples below illustrate various types of dates.

 

(for an island, the, exact day of the name designation is known)
Example

(start: 1643, end: 9999)

(for a US state, estimated searching dates for "circa")
Example

(start: 1750, end: 9999)

(for Alexandria, Egypt, estimated searching dates for a century BCE)
Example

(start: -400, end: 9999)

(for Siena, Italy, start date based on life dates of Julius Caesar)
Example

(start: -100, end: 300)

(for Vienna, Austria, estimated searching dates express a broad span of time)
Example

(start: -400, end: 1500)

 

How does the TGN handle cases where a place has unknown parents?
The TGN editorial policy is to publish places only when it is possible to determine their correct hierarchical position; however, there are exceptions. For example, when information about the internal subdivisions of a nation is changing or unavailable. In such cases, the inhabited places for that nation appear under a temporary level (called lost & found in the example below).

Example
 

Why and how do TGN records and names change over time?

The TGN data changes with every year's publication, as has been true throughout its history. Such changes are tracked automatically in the Revision History, so it is possible for licensees to analyze changes in a systematic way with each year's publication. In fact, when the data is available via APIs, they will be able to check changes regularly throughout the year.

TGN records are changed primarily for these reasons:

- Loading contributions.
- To add new records (called "subjects" in the database) or to add new names to existing subjects.
- To reflect changes in scholarship or usage of names and their definitions or scope.
- To make the data more consistent throughout. Legacy data and incoming contributed datasets occasionally require changes to existing records in order to maintain the logic and consistency of the whole.
- To place subjects in new hierarchical arrangements, as indicated by changes in the world's administrative subdivisions.
- To correct outright mistakes, either arising from contributed data or from editors' past mistakes.

The TGN has a very small staff. We rely upon the user community to grow the TGN, and we welcome users pointing out errors or inconsistencies.



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Last updated 23 May 2011

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