Among the symbols used, there are cave paintings, petroglyphs, pictograms and ideograms. Writing systems were preceded by proto-writing, which used pictograms, ideograms and other mnemonic symbols. Symbol libraries enable Inkscape to use existing symbols like logic-gate symbols or DOT pictograms. The use of pictograms and logograms in texts are present in every language. The sites specifically associated with the Austronesian expansion contain examples of indigenous pictograms and petroglyphs. The standardized form of each cuneiform sign appears to have been developed from pictograms. The colonial-era codices often contain Aztec pictograms or other pictorial elements. These drawings, known as pictograms, depicted objects and abstract concepts. Emerging in Sumer c. 3500 BC, cuneiform writing began as a system of pictograms. Arntz designed around 4000 different pictograms and abstracted illustrations for this system. Many of the pillars are decorated with abstract, enigmatic pictograms and carved animal reliefs. Sumerians used what is known as pictograms. Prohibition signs are round with white backgrounds, red borders, and blue pictograms. Mandatory instruction signs are round with blue backgrounds and white pictograms. Further pictograms and lettering can be realized with this technology.