Top elements of APML. In the presented XML schema graph notation, dotted rectangles represent optional elements and solid rectangles represent required elements. Complex types, which can be used as common element types, are defined by shaded boxes. Elements with "+" indicate there are further subelements and elements with "-" indicate that it has been expanded to display in the figure. indicates sequence type of child elements and indicates choice type of child elements. A) The apml element has two child elements. The dataProcessing element stores software information, and data element child elements of either feature list as peak_list element, or alignment feature list as alignment element. The cluster_profile element is an optional element for a list of clustered feature references in any time course or dilution series experiment. The dataProcessing element stores software information, and data element stores either feature list as peak_list element or alignment feature list as alignment element. B) The peak_lists can have one to many peak_list elements, which stores the detected features of a single LC-MS run. C) The alignment element stores all LC-MS file information in feature_source_list, and aligned features are stored in aligned_features element.