1890
For ease of practice , most of the earliest works directly tried to use existing traditional TO , or other similar structure optimization methods , for lightweight design in DfAM , without considering any AM constraints .
 concept or principle: structure optimization; concept or principle: lightweight; engineering feature: design; manufacturing process: AM
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 concept or principle: structure optimization; concept or principle: lightweight; engineering feature: design; manufacturing process: AM