Data design is planning what information your product requires, involving planning of the database.

Always require the least amount of data possible. Filling forms is boring and service seems suspicious if they require information that we see irrelevant for the service.

User Profiles

Separate frequently and rarely accessed data. Separate user login information, general user information, user privileges and user settings in the database.

Consider using email as username. If not possible, allow user to login with his username or email.

Names

You should ask user full name and what to call the user. These two fields are the only universally usable format.

Yo-Yo is a member of Ma family.
In Chinese, people write their family name first: Ma Yo-Yo.

Facts about names:

• People can have multiple names.
• People can change their names.
• People names can be case sensitive.
• People names can be written in all caps or all lower.
• People names can have prefixes and suffixes.
• People names can contain numbers.
• People can have same first and last name.
• People might be missing first and last name, but have some other form of name.
• People can have names that were not given at birth.

Emails

Always verify user emails before using them for anything.

Allow one-click unsubscription.

You can use one Gmail account for testing. Gmail discards anything after +.

username+test132@gmail.com.

Geography

Places can have multiple names.

Genève, Genf, Ginevra.
Äntlisberg, Entlisberg.

Places are not always right by the language.

üe sound is no longer used in german.
Üetliberg

Most French do not know how to even type ÿ.
Île de Croÿ

ó is not valid Frence
Béla Bartók

Not all countries have a capital.

Switzerland does not.

Country and language codes do not always match.

Japan the Country: jp
Japanese the Language: ja

Addresses

Customers do not always have fixed address with a fixed location. If you do not have an address, ask to specify landmarks, subdivision, nearby roads, mileage, neighbours.

Person can live in a boat.

Addresses do not always have a state.

United Kingdom does not have states.

Addresses do not always contain a building number. And building number is not always numeric.

Royal Opera House, Covent Garden, London, United Kingdom
Flat 1.4, Ziggurat Building, 60-66 Saffron Hill, London, United Kingdom
0 Egmond Road, Middlesbrough

Buildings can have a name and a number.

Flat 1.4, Ziggurat Building, 60-66 Saffron Hill, London, United Kingdom

Addresses can have multiple streets.

6 Elm Avenue, Runcorn Road, Birmingham, United Kingdom.

Addresses do not always have a street.

Electoral Reform Society Ltd, London, United Kingdom

Addresses can have well over 100 characters. Addresses can require well over 5 lines.

Department For Environment Food & Rural Affairs (D E F R A),
State Veterinary Service, Animal Health Office, Hadrian House,
Wavell Drive, Rosehill Industrial Estate, Carlisle, CA1 2TB,
United Kingdom

Addresses can contain commas.

Society of College, National & University Libraries,
102 Euston Street, London, NW1 2HA

Same building number can be used multiple times in one street.

50 Ammanford Road, Tycroes, Ammanford, SA18 3QJ
50 Ammanford Road, Llandybie, Ammanford, SA18 3YF

Addresses can change even if the person does not move. New postal codes.

All customers do not know their postal codes. Misreading handwritten postal codes is normal. French postcode 75015 covers over 230,000 people.

Roads can have multiple names. Roads may also be named in multiple languages.

Roads do not always have names. In Japan districts and blocks numbers are used.

Street names are not uniform in any way. E.g. there is not always 'street', 'drive', 'hill'.

Piccadilly, London, W1J 9PN

There are cases where you do not even have a postcode. And there are cases where you have multiple postcodes

Military addresses can be really complex.

BFPO, BF1 4FB -- Navy vessel HMS Example

Addresses can be coordinates like in Menomonee Falls.

N88 W16541 Foobar St.

Addresses do not always contain only Latin characters.

Χανδρή 1 & Θεσσαλονίκης, Τ.Κ. 18346, Αθήνα -- Greek tax office.

Addresses are not always written in the country's locale. There can even be mutliple characters sets in one address.

This is in Bulgaria.
Shipchenski Prohod Blvd. Block 17, Sofia, 1113

All number like zip codes can start with a zero.

All in all, you cannot validate an address.

S Hwy X