How to validate a Brazilian civil name?

Question

How to validate people’s names, in Brazilian Portuguese?

Answer 1

The Portuguese alphabet is based on latin alphabet, consisting of 26 characters:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Added to these characters, the Portuguese alphabet (from Brazil) adds the following diacritical symbols:

• ~ (Til): nasalizes the vowel "a" and the diphthongs "ae", "Oe" and "ao" -ã / ãe / õe / ão.
• ¸ (Cedilla): gives the letter "c" the sound of the letter "s" in front of "a", "o" and "u" -ç.
• ^ (Circumflex Accent): indicates the stressed syllable and closes the timbre of the vowels "a", "e" and "o", in cases where graphic accentuation -- â/ ê / ô is required.
• ´ (Acute Accent): specifies the stressed syllable and opens the timbre of vowels in cases where graphic accentuation is required -- will / is / í / ó / ª.
• ` (Grave Accent): used to mark the dative female case (à), as opposed to "to" (male), and the pronouns "that", "that" and "that" - to.
• ¨ (Trema): currently used only in Brazilian Portuguese to indicate the pronunciation of the vowel "u" in the sequences "qüe", "qüi", "Güe" and "Güi" - ü.

So beyond the traditional track a-z and A-Z, we must also include the characters ãõ, ç, âêô à, áéíóú and ü. And of course, we can’t forget the white space.

The regex would be:

[^a-zA-ZáéíóúàâêôãõüçÁÉÍÓÚÀÂÊÔÃÕÜÇ ]

Still remember to:

• Handle any blanks at the beginning and end of the name (Trim).
• Check for consecutive whitespaces.

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Example (C#)

public static string TratarNome(string nome)
{
    if (string.IsNullOrWhiteSpace(nome)) throw new ArgumentException("Um nome em branco foi passado.");

    // Removendo caracteres em branco no ínicio e no final do nome:
    nome = nome.Trim();

    // Trocando dois ou mais espaços em branco consecutivos por apenas um:
    nome = Regex.Replace(nome, "[ ]{2,}", " ", RegexOptions.Compiled);

    // Verificando a ocorrência de caracteres inválidos no alfabeto português (do Brasil):
    if (Regex.IsMatch(nome, "[^a-zA-ZáéíóúàâêôãõüçÁÉÍÓÚÀÂÊÔÃÕÜÇ ]", RegexOptions.Compiled)) throw new ArgumentException("Nome inválido: \"" + nome + "\".");

    return nome;
}

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In practice

I ran the above code on a basis of tens of thousands of Brazilian names (around 100,000).

Of these I obtained the following false positives:

• ñ: PEÑA, CAMIÑA, YÁÑEZ, MUÑOZ and MUÑIZ.
• ': SAINT'CLAIR.
• -: SAINT-CLAIR.

In addition to our colleague’s name @jpkrohling:

• ö: KRÖHLING.

Another curiosity is that a few records are blank NBSP (160), instead of the white space common SP (32). The validation also detected this (and, in our case, we decided to replace).

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Treating international names

Treating names, especially internationally, is not a simple task. The above treatment would fail as relatively common names like Björk, Marić; or not as common as Graham-Cumming.

Also, when being more permissive, beware of a possible breach of an XSS attack. An example would be the use of apostrophe. Some names use the apostrophe, which is often represented (erroneously?) by the single quote character (') instead of the correct character (’).

Be advised.

Answer 2

In Brazil there are no restrictions on the names of people. The law only mentions that it cannot expose the person to ridicule, otherwise it is allowed. And yet nothing prevents a foreigner from living in the country and needs to be registered in your system.

In this way it is no use only to provide a validation rule that considers the letters of the Latin alphabet (of A-Z) and their accents. It is also necessary to provide exceptions for apostrophes, hyphens, sequence of Roman numbers (William Gates III, for example), Greek characters... The list of exceptions would be gigantic and would probably leave something out, generating error for a specific user.

There is also the problem of encodings, and depending on the treatment that the related systems give to the characters, a name could be printed in another system in a totally incomprehensible way.

In general, if you prevent a user from registering on your system because their name is not accepted, you are losing a potential customer. Only validate if the field has been filled and does not take risks.