1. APPCs
revisited
2/25/2019
APPCs revisited

2. APPCs: motivation Want classes and collaborations
Want variation-oriented programming
incremental change of collaborations by code addition instead of individual class editing
Want traversal strategies
structure-shyness and partially automated evolution
2/25/2019
APPCs revisited

3. Composition of APPCs, strategies and class graphs
Strategy types
gv gv2
st1
st1
st1 s1
s1 = refinement of
st1 for CG1
Class graphs
gv1
CG1
CG2
gv2(gv1)(s1 CG1) s1
gv2
instantiated
behavior
2/25/2019
AOO

4. Loose coupling C S Strategy graphs Class graphs Each unit should
hard-code as few
assumptions as possible
on the concrete form
of the others. F
APPCs
2/25/2019
AOO

5. Roles of strategy graph
Participant management role
define set of participants reachable from a class-valued variable
define participant transportation
participant name : abbreviation for path or reversed path
Super-iterator role
iterate while executing code of some APPC
2/25/2019
APPCs revisited

6. Roles of strategy graph
Participant management role
forward path abbreviation
From a:A via b:B to c:C
if unique path, c is abbreviation for path (used in A-object or B-object)
backward path abbreviation
if in C-object we need the last B-object visited, b is abbreviation for reversed unique path (used in C-object)
2/25/2019
APPCs revisited

7. Participant management role
Interesting definition: unique reverse path
PartList
Loop does not matter
for reverse path
ClassDef
Part
Empty
NonEmpty
Reverse path from Part to ClassDef is unique.
2/25/2019
APPCs revisited

8. Super-iterator role
Traverse and execute code of an APPC (visitor style).
o.strategy(APPC)
can be anywhere in a method
f() strategy(APPC)
introduce name f and then call o.f()
2/25/2019
APPCs revisited

9. Playing both roles
Participant management role and super-iterator role.
Adjacency to edge-list translation
participant transportation along unique backward paths (backward path abbreviation)
use same strategy as super-iterator
Pricing
set of participants along unique paths (forward path abbreviation)
us same strategy as super-iterator
2/25/2019
APPCs revisited

10. APPC Consists of provided interface required interface implementation
methods to class-valued variables
output port to other components
required interface
methods from class-valued variables
interface to class graph: paths required
input ports from other components
implementation
2/25/2019
APPCs revisited

11. APPC Required interface methods from class-valued variables
interface to class graph: paths required
A set of traversal strategies
for participant management (unique forward and backward paths)
as super-iterators
input ports from other components
2/25/2019
APPCs revisited

12. APPC Implementation methods: refer to participants methods may call
next(): result from next component
next().n: result from component n
subtraversal().s: continue traversal following strategy edge s ????
2/25/2019
APPCs revisited

13. Compositionality and referring to traversals in APPC code
Should keep it simple: go_on() (or next()) should be only way to talk about what to do next.
Reason: we want to compose several APPCs and if each of them talks about its own way of navigation, it is not clear what composition means
2/25/2019
APPCs revisited

14. Kinds of APPCs Visitor style Adjuster style
single-traversal collaborations
addition or modification for duration of traversal
Adjuster style
multi-traversal collaborations
add statically new methods to groups of classes
statically modify methods in groups of classes
2/25/2019
APPCs revisited

15. Both kinds Parameterized by strategies class-valued variables
method-valued variables
2/25/2019
APPCs revisited

16. Kinds of APPCs Visitor style single-traversal collaborations
single strategy parameter, uniform single method name backbone of collaboration
calls subtraversal().s // follow down strategy edge s ????
2/25/2019
APPCs revisited

17. Kinds of APPCs Adjuster/Contract style multi-traversal collaborations
several strategy parameters
different method names
2/25/2019
APPCs revisited

18. Role of strategy graph
At some class A we don’t call next() only. Can call subtraversal().x and subtraversal().y with any Java code in between. ???
Strategy graph describes where we might traverse: is the case anyway with around methods. ???
2/25/2019
APPCs revisited

19. APPCs: visitor style APPC A (St1 s1){ instance variables methods
B { // redefines node code
instance variables, methods
void my_role(){
{ … next(); … } }
-> X,y,Y { // redefines edge code
void my_role() { … next(); … }
St1 strategy type
describing the collaboration.
K,L appear in St1
2/25/2019
APPCs revisited

20. Structure of an APPC (visitor style)
APPC (Strategy s, Method m1,…,mk){
// visitor style has only one strategy argument
//variables global for traversal
init()…
return()…
start()…
final()…
s.source
//variables that temp. extend host object
my_role()
host.m1();… next-visitor.return;… next();
host.localMethod1();…
}// end of APPC
2/25/2019
AOO

21. APPC: adjuster style APPC A (St1 s1, St2 s2, …){ B { void f1() {
{ x.f2(); … next(); …} }
C {
void f2() { …
Add new methods f1 and f2 to classes
B and C, respectively.
2/25/2019
APPCs revisited

22. Open issues Composition of APPCs
order
modifies/assumes/extends
uses
Integrate visitor style and adjuster style?
Visitor a special case of adjuster style
Injecting APPCs into class graph
2/25/2019
APPCs revisited

23. Open issues Subtraversals: strategic traversal automaton
using APPCs as arguments to other APPCs or parts of them
like a uses relationship
2/25/2019
APPCs revisited