Class relationship in UML notation. The class seqdb consists of 3 classes: SeqInfo, BioSeq, and Feature. The class nsdb comprises 4 classes: EmblSeq, NucFeature, FeatureLocation and Embl. EmblSeq inherits from the classes of EntryInfo, SeqInfo and NucSeq that in turn inherits from BioSeq. FeatureLocation inherits from Location, and NucFeature inherits from Feature.