Public art program
The standing municipal or institutional structure (staff, policy, budget) through which public art is commissioned, maintained, and managed, rather than delivered as one-off projects.
The usual anatomy: a public art officer or administrator inside a cultural affairs or planning department, an advisory committee or arts commission for selection and policy, a funding mechanism (often percent-for-art), and, in the mature programs, a maintenance budget with the collection's name on it.
The program is what persists between projects. Individual commissions come and go, but the records, the artist relationships, the selection precedents, and the maintenance schedule are the actual asset. Cities without a program can still end up with plenty of art; what they can't end up with is a collection anyone is accountable for.