## 3 About Geographic Names and Gazetteers
### Generalities
Among place names, there are street names together with the number in the street (civic number); these are not so easy to handle. This is very important, not only for the automatic processing of postal addresses, but also for all applications connected to an emergency. The Urban and Regional Information Systems Association (URISA) association has organized many conferences on the topic (see [19]). The specificities of street names are as follows:  
* some streets comprise a few dozens of yards, whereas others several miles;
* in some human settlements, streets have no names;
* sometimes, there are variations about the way to write some street names; for instance \"3 rd Street\", \"Third Street\", \"Third St\"; the words \"avenues\" and \"boulevards\" are commonly simplified into \"Ave\" and \"Blvd\" or \"Bd\";
* in some countries, the equivalent of the words \"street\", \"avenue\", _etc._, are usually removed;
* in some places, streets can have several names; for instance, in New York City, \"Sixth Avenue\" is also known as \"Avenue of the Americas\";  
As a main consequence, the name of a place cannot be a unique ID from a computing point of view. In order to clarify, let us give a few definitions:  
* toponym is the general name of a geographic feature;
* endonym is a local name in the official language of the country or in a well-established language occurring in that area where the feature is located; there may be several toponyms in countries with different official languages (Brussel in Flemish, Bruxelles in French);
* exonym is a name in languages other than the official languages; for instance Brussels in English;
* archeonym is a name that existed in the past: for instance, Byzantium for Istanbul;
* hyperonym and hyponym are the names of places with a hierarchy; hyponym is the opposite of hyperonym; for instance, Europe is a hyperonym of France, whereas France is a hyponym of Europe;
* meronym is a name of a part of a place without a hierarchy; sometimes the expression partonym is used; for instance \"Adriatic Sea\" is a meronym of the Mediterranean Sea;
* hydronym is a name of a waterbody;  
Figure 5: Very complex many-to-many relations link places and their names. * oronym is a name for a hill or a mountain;  
Figure 6 gives the essential elements of a gazetteer, the names, the features, the dates and everything regarding geometry and georeferencing according to [20]. In addition, places, such as airports, can have several names. Sometimes, their International Air Transport Association (IATA) [21] codes are used: the well-known New York airport, John F. Kennedy International Airport, is often referred to as JFK airport. Zip codes or postcodes can also be considered as toponyms. However, the definition of postcodes differs according to country: In some cases, one postcode can correspond to a few houses, and in others some hundred thousand inhabitants. To conclude this section, in an automatic system for searching geographic information in the web (often known as GIR, geographic information retrieval), a preliminary phase of disambiguation is necessary, since the name can correspond to something that is not geographic (Figure 7). Let us define as a literal a string of characters (perhaps including blank spaces, hyphens and numbers): this literal may be a toponym, the name of a person (Washington) or something else (China and porcelain). Toponyms can be described as literals.