rdf2owl: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/rdf2owl - from package: libowl-directsemantics-perl

You may install the required package with command apt-get install {package}

Error in other languages:
rdf2owl: bevel nie gevind nie
rdf2owl: comandă negăsită
rdf2owl: comando não encontrado
rdf2owl: commande introuvable
rdf2owl: command not found
rdf2owl: käsku ei ole
rdf2owl: không tìm thấy lệnh
rdf2owl: komanda nerasta
rdf2owl: Kommando nicht gefunden.
rdf2owl: kommandot finns inte
rdf2owl: komut yok
rdf2owl: nie znaleziono polecenia
rdf2owl: níor aimsíodh an t-ordú
rdf2owl: no se encontró la orden
rdf2owl: no s'ha trobat l'ordre
rdf2owl: opdracht niet gevonden
rdf2owl: parancs nem található
rdf2owl: perintah tidak ditemukan
rdf2owl: príkaz nenájdený
rdf2owl: příkaz nenalezen
rdf2owl: команда не найдена
rdf2owl: командата не е открита
rdf2owl: 命令找不到
rdf2owl: コマンドが見つかりません