SequenceML deals with all kinds of simple sequence information often used as input for several common bioinformatics tools. It is designed to be used as a replacement for the FASTA format, containing all of FASTA's information content while avoiding that format's aforementioned consistency problems. SequenceML differentiates between nucleic- and aminoacid sequences following the IUPAC standard and also allows the user to add free sequence information based on basic types defined by BioTypes. SequenceML also supports a mandatory sequence id and an optional detailed sequence description. In difference to previous versions SequenceML >3.0 offers the possibility to add simple annotations. Synonyms for this element Element for annotation of sequence data. Contains one or more positions associated with a set of properties, which can be freely defined. Optional attributes allow for specification of annotation source (e.g. the generating program), creation date and a human readable description of the meaning of this annotation. Definition of an annotation property, identified by 'key' attribute, with optional human readable description. Location information for annotation. Optional strand attribute for e.g. nucleic acid sequences.