Firstly, data objects in biological data sources often take the form of a hierarchically nested structure with their components missing, repeat, ordered and/or unordered. This results in the structural complexity of data objects.

• 首先,生物数据源中的数据对象具有结构复杂性:数据对象往往具有多层嵌套结构,对象的成分可以缺失、多次重复、有序出现或无序出现;