Should package names be singular or plural?

Often, in libraries especially, packages contains classes that are organized around a single concept. Examples: xml, sql, user, config, db. I think we all feel pretty naturally that these packages are correct in the singular. com.myproject.xml.Element com.myproject.sql.Connection com.myproject.user.User com.myproject.user.UserFactory However, if I have a package that actually contains a collection

[kadoyau]

HogeTask, FugaTaskという複数種類のtaskがあれば複数形（Tasks）。TaskFactory TaskHandlerのようなtaskに関する異なる役割のクラスがある場合は単数形（Task)

[gfx]

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