Algorithms help unravel the secrets of ancient documents

B-G University project discovers Hebrew prayers under Arabic lettering.

Torah 88 248 (photo credit: Courtesy)
Torah 88 248
(photo credit: Courtesy)
Computer science and humanities departments have joined forces at Ben-Gurion University in Beersheba to decipher historical Hebrew documents, a large number of which have been overwritten with Arabic stories. The texts include fragments of Jewish prayer books from the Land of Israel. The unique algorithm being used to determine the wording was developed by BGU computer scientists. The documents are searched electronically, letter by letter, for similarities in handwriting which help determine the date and author of the texts. The documents being deciphered at BGU are degraded texts from sources such as the Cairo Geniza, the Al-Aksa manuscript library in Jerusalem, and the Al-Azar manuscript library in Cairo. All together, the base consists of "100,000 medieval Hebrew codices and their fragments [that] represent the book production output of only the last six centuries of the Middle Ages," BGU computer science professor Klara Kedem said this week. Kedem has presented the new algorithm to other universities and research centers so a large number of texts can be deciphered. The purpose of the project is to classify the handwritten documents and determine their authorship. One problem is that many of the original Hebrew texts which were found in the Cairo Geniza have been scratched off, and the parchment used to write an Arabic text. Ehrlich, head of the Prayer Research Project at BGU, explained, "There was one book, found in the Geniza and which is now in Italy, but which was originally used as a Hebrew prayer book." However, the book had been rewritten as an Arabic text. "Our aim was to read the first book and not the second book. So we needed to find out how the Arab book could disappear and would leave only the Hebrew letters of the original book. This is why the computer sciences and humanities departments at BGU decided to collaborate," Ehrlich said. "Although the texts are in Hebrew, the task of deciphering what is written is difficult because the historical documents have degraded over time," Kedem said. "Now, the foreground and background lettering are hard to separate and there are smudges on the ink of much of the text which intensifies the background coloring. Furthermore, ink from the alternate side of the document adds blotches to the lettering." To solve the problem, the algorithm is used to cover the text in a dark grey color, which then highlights lighter colored pixels as background space and identifies the darker pixels as outlining the original Hebrew lettering. There are two separate academic disciplines interested in driving this project forward. First, linguistic specialists seek to gain a deeper appreciation of the origins of the Hebrew language. Second, Jewish philosophers are interested in studying ancient forms of prayer that are thought to be contained in the texts. Ehrlich is particularly interested in deciphering the texts which are thought to include ancient prayers, so that the translations can be added to BGU's The Prayer in Rabbinic Literature Database Collection. Most of the fragments which contain prayers were found in the Cairo Geniza. However, few documents remain fully intact, and "we are trying to piece them together like a big puzzle," Ehrlich said. It is unsurprising that prayers were found in the Cairo Geniza, because it was there that Jews buried their sacred material when they had no further use for it. Many of the fragments originate from Jewish communities in the Land of Israel between the 9th and 11th centuries. The texts arrived in Cairo because there were two big Jewish communities in that city. One synagogue followed the Babylonian Jewish traditions and prayers, and the other followed the Land of Israel traditions and liturgy. "It is very difficult to estimate the value of these fragments, but they would be very expensive," said Ehrlich. Most fragments which have been discovered at the Cairo Geniza are now in museums at Cambridge and Oxford universities, The British Museum and in Israel and Paris. Until now the documents have not been researched systematically. With the new algorithm, researchers hope to create a catalogue of all the texts and piece together the ancient prayers and other documents, including those citing Jewish law.