Despite the rapid growth of Unicode in the last few years, the sad fact is that many text editors and other tools are still tied to platform- and nationality-dependent character sets such as Windows-1252, MacRoman, and SJIS. The only characters all these sets have in common are the 128 ASCII letters, digits, punctuation marks, and control characters. These characters are the only ones that can be reliably displayed and edited across the wide range of computers and software in use today. Thus, if it's not too big a problem, try to limit your markup to the ASCII character set. If you're writing in English, this is normally not a problem.

On the other hand, this principle is not written in stone, especially if you're not working in English. If you're writing a simple vocabulary for a local French bank without any international ambitions, you will probably want to include all the accents commonly used in French for words like relevé (statement) and numéro (number). For instance, a bank statement might look like this:

<?xml version="1.0" encoding="ISO-8859-1"?>
<Relevé xmlns="http://namespaces.petitebanque.com/">
  <Banque>PetiteBanque</Banque>
  <Compte>
    <Numéro>00003145298</Numéro>
    <Type>épargne</Type>
    <Propriétaire>Jean Deaux</Propriétaire>
  </Compte>
  <Date>2003-30-02</Date>
  <SoldeDOuverture>5266.34</SoldeDOuverture>
  <Transaction type="dépôt">
    <Date>2003-02-07</Date>
    <Somme>300.00</Somme>
  </Transaction>
  <Transaction type="transfert">
    <Compte>
      <Numéro>0000271828</Numéro>
      <Type>courant</Type>
      <Propriétaire>Jean Deaux</Propriétaire>
    </Compte>
    <Date>2003-02-07</Date>
    <Somme>200.00</Somme>
  </Transaction>
  <Transaction type="dépôt">
    <Date>2003-02-15</Date>
    <Somme>512.32</Somme>
  </Transaction>
  <Transaction type="retrait">
    <Date>2003-02-15</Date>
    <Somme>200.00</Somme>
  </Transaction>
  <Transaction type="retrait">
    <Date>2003-02-25</Date>
    <Somme>200.00</Somme>
  </Transaction>
  <SoldeDeFermeture>5478.64</SoldeDeFermeture>
</Relevé>