gistfile1.clj

(def *expected-selectors* [[:id] [:published] [:updated]
                           [[:link (e/attr= :rel "edit")]] 
                           [[:link (e/attr= :rel "alternate")]]])

(def *entry-template* (e/xml-resource "templates/entry.xml"))

(defn normalize-entry [entry]
  (e/transform entry [:entry]
    (e/do->
      (for [sel (filter #(empty? (e/select entry %)) *expected-selectors*)]
        (e/append (e/select *entry-template* sel))))))

Here is a solution:

;; selectors of elements expected to be found on an Entry
(def *expected-selectors* [[:id] [:published] [:updated]
                           [[:link (e/attr= :rel "edit")]] 
                           [[:link (e/attr= :rel "alternate")]]])

(defn normalize-entry [entry]
  (e/transform entry [:entry]
    (e/append
     (for [sel (filter #(empty? (e/select entry %)) *expected-selectors*)]
       (e/select (e/xml-resource "templates/entry.xml") sel)))))