The document discusses using logic meta-programming to query software history stored in repositories. It describes using tools like Ekeko, QWAL and a history model to query characteristics of code across multiple versions using logic rules. Regular path expressions allow formulating complex queries over the graph of program elements and their changes over time. Future work includes enhancing the history model and scaling the approach to larger projects.

1. Querying the History
of a Software Project
Reinout Stevens
resteven@vub.ac.be
@ReinoutStevens
1

2. Context
Mining Software
Repositories
2

3. Context
Program
Comprehension
Using Information Fragments to Answer the Questions Developers Ask
Thomas Fritz and Gail C. Murphy
International Conference on Software Engineering (ICSE), p.175--184, 2010
3

4. Context
Program Development Process
Comprehension Verification
Using Information Fragments to Answer the Questions Developers Ask
Thomas Fritz and Gail C. Murphy
International Conference on Software Engineering (ICSE), p.175--184, 2010
3

5. Logic Meta-Programming
• Querying a single program version.
• Describe characteristics of the code.
• Ekeko, PQL, CodeQuest, JTL, SOUL, ...
4

6. History Query Tool
{
Temporal Query Language
Repository Representation
Program Query Language
5

7. Implementation
{
Regular Path Expressions
Git + Eclipse Model
Ekeko
6

8. RPE
Core.logic Eclipse
Ekeko
(defrel parento parent child)
(fact parento ‘bob ‘alice)
(fact parento ‘kate ‘alice)
(fact parento ‘bob ‘chris)
(fact parento ‘kate ‘chris)
(defn sibling [?x ?y]
(fresh [?parent]
(parento parent ?x)
(parento parent ?y)
(!= ?x ?y)))
> (run* [?sib]
(sibling 'alice ?sib))
(chris chris)
https://github.com/clojure/core.logic/
7

9. RPE
Core.logic ctd’ed Eclipse
Ekeko
(sibling 'alice ?sib)
> (run* [?sib]
(sibling 'alice ?sib))
(chris chris) (fresh [parent]
(parento parent 'alice)
(parento parent ?sib)
(!= 'alice ?sib)))
;; parent -> 'bob ;; parent -> 'kate
(parento 'bob ?sib) (parento 'kate ?sib)
(!= 'alice ?sib) (!= 'alice ?sib)
;; parent -> 'bob ;; parent -> 'bob ;; parent -> 'kate ;; parent -> 'kate
;; ?sib -> 'alice ;; ?sib -> 'chris ;; ?sib -> 'alice ;; ?sib -> 'chris
(!= 'alice 'alice) (!= 'alice 'chris) (!= 'alice 'alice) (!= 'alice 'chris)
8

10. RPE
Ekeko Eclipse
Ekeko
+
(ekeko* [?m ?value]
(damp.ekeko.jdt.reification/ast :MethodDeclaration ?m)
(damp.ekeko.jdt.reification/has :name ?m ?value))
https://github.com/cderoove/damp.ekeko
9

11. RPE
History Model Eclipse
Ekeko
+
https://github.com/ReinoutStevens/damp.scrapperplugin
10

12. RPE
QWAL Eclipse
Ekeko
foo bar baz quux
1 (run* [end]
2 (qwal graph start end
3 []
4 (qcurrent [curr] (has-info curr :foo))
5 q=>
6 (qcurrent [curr] (has-info curr :bar))
7 q=>
8 (qcurrent [curr] (has-info curr :baz))
9 q=>
0 (qcurrent [curr] (has-info curr :quux)))))
Universal regular path queries
Oege De Moor and David Lacey and Eric Van Wyk
https://github.com/ReinoutStevens/damp.qwal
11

13. RPE
QWAL Eclipse
Ekeko
foo bar baz quux
1 (run* [end]
2 (qwal graph start end
3 []
4 (qcurrent [curr] (has-info curr :foo))
5 q=>
6 (qcurrent [curr] (has-info curr :bar))
7 q=>
8 (qcurrent [curr] (has-info curr :baz))
9 q=>
0 (qcurrent [curr] (has-info curr :quux)))))
Universal regular path queries
Oege De Moor and David Lacey and Eric Van Wyk
https://github.com/ReinoutStevens/damp.qwal
11

14. RPE
QWAL Eclipse
Ekeko
foo bar baz quux
1 (run* [end]
2 (qwal graph start end
3 []
4 (q=>*
5 (qcurrent [curr]
6 (fresh [info]
7 (has-info curr info))))
8 (qcurrent [curr] (has-info curr :quux))))
12

15. RPE
QWAL Eclipse
Ekeko
(q=>* & goals)
(q=>+ & goals)
(q? & goals)
https://github.com/ReinoutStevens/damp.qwal
13

16. NoName
1 (run* [?name1]
2 (fresh [?end ?method1 ?method2 ?name2]
3 (qwal graph root ?end
4 []
5 (q=>*) ;;skip arbitrary number of versions
6 (qcurrent [current] ;;in this version do
7 (ast :MethodDeclaration ?method1) ;;find a method
8 (has :name ?method1 ?name1)) ;;with a name
9 (q=>+) ;;skip arbitrary number of versions, >1
0 (qcurrent [current] ;;in this version do
1 (ast :MethodDeclaration ?method2) ;;find a method
2 (has :name ?method2 ?name2) ;;with a name
3 (!= (get-identifier ?name1) ;;that is different from
4 (get-identifier ?name2));;the previous method
5 (has-same-body ?method1 ?method2)))))
14

17. Future Work
• Extend History Model
• Unification across versions
• Detect and precompute refactorings
• Large-scale projects
• Include other sources of information
• Semantic Patches
15