Liliendahl on Data Quality

Using postal addresses is a core element in many data quality improvement and master data management (MDM) activities.

As touched many times on this blog postal addresses are formatted very differently around the world. However they may all be arranged in a sort of hierarchy, where there are up to 6 general levels being:

• Country
• Region
• City or district
• Thoroughfare (street) or block
• Building number
• Unit within building

In addition to that the postal code (postcode or zip code) is part of many address formats. Seen in the hierarchical light the postal code is a tricky concept as it may identify a city, district, thoroughfare, a single building or even a given unit within or section of a building. The latter is true for my company address in the United Kingdom, where we have a very granular postcode system.

Country

As discussed in the post The Country List even the top level of a postal address hierarchy isn’t a simple list fit for every purpose. Some issues are:

• There are different sources with different perceptions of which are the countries on this planet
• What we regard as countries comes in hierarchies
• Several coding systems are available

Region

The region is an element in some address formats like the states in the United States and the provinces in Canada, while other countries like Germany that is divided into quite independent Länder do not have the region as a required part of the postal address. The same goes for Swiss cantons.

City or district

I once read that if you used the label city in a web form in Australia, you would get a lot of values like: “I do not live in a city”.

Anyway this level is often (but as mentioned certainly not always) where the postal code is applied. The postal code district may be a single town with surroundings, several villages or a district within a big city.

Thoroughfare (street) or block

Most countries use thoroughfares as streets, roads, lanes, avenues, mews, boulevards and whatever they are called around. Beware that the same street may have several spellings and even several names.

Japan is a counterexample of the use of thoroughfares, as here it’s the blocks between the thoroughfares that are part of the postal address.

Building number

Usually this element will be an integer. However formats with a letter behind the integer (example: 21 A) or a range of integers (example: 21-23) are most annoying. And then this British classic: One Main Grove. OMG.

Unit within a building

This element may or may not be present in a postal address depending on if the building is a single family house or company site, the postal delivery sees it as such or you may actually indicate where within the building the delivery goes or you go. The ups and downs of this level are examined in the post A Universal Challenge.