+/**
+ * \brief Delete all tuples matching to the query \ref tuple fromt the
+ * \ref relation.
+ *
+ * \param r is the \ref relation concerned.
+ *
+ * \param t is the \ref tuple to delete.
+ *
+ * \returns a \vector vector of all knocked out tuples, i.e. the
+ * same-key tuples, if any, contained in the relation
+ *
+ * Note that deletion uses a "query" tuple, which means that some
+ * columns may be null to mark that them match to any value.
+ *
+ * \related relation
+ */
+extern vector *relation_delete(relation *r,tuple *query);
+
+/**
+ * \brief Return the next \ref tuple in the \ref relation that matches
+ * to the query \ref tuple, at or after the index.
+ *
+ * \param r is the \ref relation concerned.
+ *
+ * \param index is a pointer to the \ref vector index to update.
+ *
+ * \param query is a query \tuple tuple for selection of certain
+ * column values.
+ *
+ * \returns any such matching \tuple tuple and an updateed *index.
+ *
+ * \related relation
+ */
+extern void *relation_next(relation *r,vector_index *index,tuple *query);
+