Describe the two alternative for specifying structural constraints on relationships types?

They are the cardinality ratio and participation constraints.

Explanation:

The Cardinality Ratio: This is for the binary relationship that specifies the max number of instances of relationships in which an entry can take part in. As an example, the Student Of binary relationship form, School: Student, the cardinality ratio of this is 1: N. and that means each of the schools can be mapped to any number of students, however, one student can be mapped to only one school. And various possible cardinality ratios for various types of binary relationships can be 1: N, N:1, 1:1, and M: N.

Participation constraint: This stipulates that an entity being be contingent upon another entity through relationship form. And it stipulates the least figure of instances of relationship which each of the entity can indulge in, and is often termed as least cardinality constraint. And we have participation types: partial and total.