I.3 Introduction to Geographic Retrieval Consistency
In applications that retrieve data from an application file by geographic location or match two application files by geographic location, the consistency of that retrieval or matching is a critical consideration that arises when processing any type of location that can be specified in more than one way. For example, consistency is a consideration for any type of location involving streets (such as addresses, intersections and street segments), since many streets have alternative names and many street names have spelling variants. The goal is to enable applications to retrieve records independently of which street name spelling was used when the record was created and which one is used at retrieval time. Similarly, consistency is a consideration when retrieving building-level data by address, since many buildings have more than one address. It is a consideration when retrieving data for street intersections, since many intersections (e.g., three-way intersections) can be specified using more than one pair of streets.
The achievement of retrieval consistency can greatly improve an application’s ‘hit’ rate on geographic searches into the application’s own files. Moreover, it enables applications to identify and consolidate multiple records for the same location effectively. These advantages can have a significant impact on the efficiency of a city operation. For example, an application can use this capability to generate a single work order for dispatching personnel to handle multiple repairs, inspections or other transactions for the same location.
Of the services that Geosupport provides, its use to achieve geographic retrieval consistency involves the most extensive integration of Geosupport in the design of the user application. Geosupport provides such support by returning certain data items which an application can store in its file during record creation and use as part of a geographic retrieval key. An example is an item called the five-digit street code, which applications can use to achieve consistent retrieval of data by those types of geographic locations that are specified in terms of streets. This is briefly discussed below, and is explained in detail in later chapters.
Within Geosupport, a set of numeric street codes has been assigned to represent New York City’s street names. A full street code is a ten-digit item that, together with a borough identifier, corresponds to a specific spelling of a specific name for a specific street in that borough. The first five digits of the ten-digit street code are collectively called the five-digit street code. Ten-digit street codes are assigned in such a way that alternative names and spelling variants of the same street have the same five-digit street code. As a result, applications can achieve consistent retrieval or matching of application data by any type of geographic location that involves streets by using five-digit street codes instead of street names as part of the retrieval key. For the convenience of users, for all functions that involve street input except Function 1N and the display functions (Functions D, DG and DN), applications have the option to provide input streets to Geosupport in the form of either street names or street codes. Street codes are discussed in greater detail in Chapter IV.