Vladislav was a nephew and successor of Duke Borna

Borna of Croatia

Borna was the Knez of Littoral Croatia in 803–821 under the Frankish Empire. He was the son of his predecessor, Višeslav.- Ruler of Dalmatia :...

 of Littoral Croatia. He reigned, as Duke of Littoral Croatia, from February 821 to ca. 835.

Most information about Vladislav is carried by the Royal Frankish Annals

Royal Frankish Annals

The Royal Frankish Annals or Annals of the Kingdom of the Franks ,are annals covering the history of early Carolingian monarchs from 741 to 829. Their composition seems to have soon been taken up at court, providing them with markedly official character...

 when it speaks about Borna

Borna

Borna is a town in the Free State of Saxony, Germany, capital of the Leipzig district. It is situated approx. 30 km southeast of Leipzig. It has approx. 21,000 inhabitants.-History:Borna as a town is more than 750 years old....

's death. It is uncertain until what year Vladislav was active as a monarch, however most historians cite the year 835 as an approximate end of his rule.
Duke Vladislav ruled from Nin

Nin, Croatia

Nin is a town in the Zadar county of Croatia, population 1,256 , total municipality population 4,603 .Nin was historically important as a centre of a Christian Bishopric in the Middle Ages. Up to the abolition and Latinization imposed by King Tomislav in the first half of the 10th century, Nin was...

 as a loyal vassal of the Frankish

Franks

The Franks were a confederation of Germanic tribes first attested in the third century AD as living north and east of the Lower Rhine River. From the third to fifth centuries some Franks raided Roman territory while other Franks joined the Roman troops in Gaul. Only the Salian Franks formed a...

 Emperor Lothair I

Lothair I

Lothair I or Lothar I was the Emperor of the Romans , co-ruling with his father until 840, and the King of Bavaria , Italy and Middle Francia...

.