Discussion with Gregor Kiczales at UBC

1
Discussion with Gregor Kiczales at UBC

• Ontology of AOP
• Ontology is the study of what there is, an
  inventory of what exists. An ontological
  commitment is a commitment to an existence claim
  for certain entities.
• Slides 2 - 5 and the last one are Gregors

An ontology is, in simple terms, a collection of
concepts with relations among them plus
constraints on the relations.
2
basis of crosscutting

• a join point model (JPM) has 3 critical elements
• what are the join points
• in AspectJ
• points in runtime call graps members
• means of identifying join points
• in AspectJ
• signatures (plus )
• means of specifying semantics at join points
• in AspectJ
• advice
• define members

3
basis of crosscutting

• a join point model (JPM) has 3 critical elements
• what are the join points
• in AspectJ
• points in runtime call graph
• class members
• means of identifying join points
• in AspectJ
• pointcuts
• member signatures (plus )
• means of specifying semantics at join points
• in AspectJ
• advice
• define members

dynamic JPMstatic JPM
4
range of AOP languages
means of join points means of join points
JPM join points identifying specifying semantics at
AspectJ dynamic JPM points in execution call, get, set signaturesw/ wildcards other properties of JPs advice
static JPM class members signatures add members
Composition Filters message sends receptions signature property based object queries wrappers declarative (filters) imperative (advice)
Hyper/J members signatures add, compose (and remove) members
Demeter traversals when traversal reaches object or edge class edge names define visit method
5
range of AOP languages
See next slide for changes to Demeter
6
range of AOP languages
means of join points means of join points
JPM join points identifying specifying semantics at
AspectJ dynamic JPM points in execution call, get, set signaturesw/ wildcards other properties of JPs advice
static JPM class members signatures add members
DemeterJ, Demeter/C dynamic JPM static JPM 1 static JPM 2 static JPM 3 when traversal reaches object or edge class members class members class members visitor method signatures traversal spec. s class graph g class names class graph visitor method bodies s g (result traversal implementation) add members class graph with tokensgrammar (result parsing and printing implementation)


7
range of AOP languages
8
Composing join point models

• Traversal Spec JPM In Demeter we use traversal
  specifications and the class graph to define a
  traversal implementation (either static or
  dynamic)
• Visitor JPM The result of Traversal Spec. JPM is
  used to define a second JPM
• The traversal implementation defines nodes and
  edge visits.
• Visitor signatures define the nodes and edges
  where additional advice is needed they are the
  means of identifying join points.
• The means of specifying semantics at join points
  are the visitor bodies.

9
DJ dynamic JPM 3

• The join points are nodes in object graphs. They
  are not dynamic call graph join points nor class
  members!
• The means of identifying the join points for a
  given object graph o are a strategy s and the
  class graph g. o must conform to g.
• The means of specifying the semantics at the join
  points are again s and g. See paper with Mitch
  Wand for the formal details behind this JPM.

10
DemeterJ static JPM 1

• The means of identifying the join points and of
  specifying the semantics at the join points are
  the same.
• The reason is that sg both
• select the classes that will get traversal
  semantics
• determine the details of the traversal semantics

11
DemeterJ static JPM 3

• The means of identifying the join points (class
  members) is done by the class graph.
• When we add tokens to the class graph we get a
  grammar that contains instructions for parsing
  and printing behavior.
• A grammar is an aspect (external representation
  aspect) the adhoc implementation cuts across all
  classes.

12
AO design in UML
Clarke, Walker

• foo
• dynamic JPM ( AspectJ)
• what happens in pattern
• bar

• Composition Patterns
• static JPM ( Hyper/J)
• binds pattern to base code
• UML class interaction diagrams already crosscut
• by-class vs. by-interaction organizations

13
Masuhara/Kiczales Modeling Framework for AO
Mechanisms

• A and B languages
• X result domain of weaving process
• XJP join points in X
• AID, BID identify join points in X
• AEff, BEff effecting semantics at jps
• META parameterize weaving process

14
Masuhara/Kiczales Modeling Framework for AO
Mechanisms

• X
• XJP
• A
• AID
• AEff
• B
• BID
• BEff
• META

15
Demeter static JPM 1 special case of Open Classes
Adds traversal methods to a set of classes

• X
• Combined program
• XJP
• c declarations
• A
• c declarations including the class graph
• AID
• Method signatures
• AEff
• B
• Traversal specifications
• BID
• c names
• BEff
• META
• Traversal semantics rules for translating
  traversal specifications to methods

16
Demeter static JPM 2 Open Classes

• See paper.

17
Demeter static JPM 3 special case of Open Classes
Adds parsing methods to a set of classes

• X
• Combined program
• XJP
• c declarations
• A
• c declarations including the class graph
• AID
• Method signatures
• AEff
• B
• Class dictionary (class graph enhanced with
  tokens defining the syntax addition)
• BID
• c names
• BEff
• META
• rules for translating class dictionary to parsing
  methods

18
Demeter dynamic JPM 1 special case of Pointcuts
and Advice
Adds advice to traversal methods

• X
• Traversal execution
• XJP
• Arrival at each object and has-a edge
• A
• Traversal methods
• AID
• Method signatures
• AEff
• Execute traversal method body
• B
• Visitor method declarations (serves as advice)
• BID
• Visitor method signatures (serves as pointcut)
• BEff
• Execute visitor method bodies
• META
• none

19
Demeter dynamic JPM 2 special case of TRAV

• For methods fetch, gather and asList special
  advice

20
Demeter dynamic JPM 3

• X
• Object graphs
• XJP
• Nodes in object graphs
• A
• Class graph
• AID
• Class names
• AEff
• B
• Traversal specification
• BID
• Class names
• BEff
• Edges to traverse at node in object graph
• META
• Rules for traversal order depth-first,
  breadth-first, left-to-right, etc.

21
Demeter dynamic JPM 4 DJ with Functional Visitor

• X
• Traversal execution with runtime control
  (Subtraversal.apply(..))
• XJP
• Arrival at each object (Functional Visitor only
  available to nodes)
• A
• Regular Java Program (class/fields declarations)
• AID
• Class/fields signatures
• AEff
• Provide reachability (my understanding is to
  construct object graph conforming to the class
  graph)
• B
• Traversal specification and visitor method
  declarations (including the default one
  combine(..))
• BID
• Visitor method signatures (or the built-in
  semantics, for the combine(..))
• BEff
• Execute the visitor methods and compute and
  combine the values and provide the runtime
  control over the traversal(subset of the
  traversal graph computed from the traversal
  specification)
• META

Mixes two models together
22
Demeter dynamic JPM 4 DJ with Functional Visitor

• X
• Traversal execution with runtime control
  (Subtraversal.apply(..))
• XJP
• Arrival at each object (Functional Visitor only
  available to nodes)
• A
• Regular Java Program defining traversals
  (class/fields declarations)
• AID
• Method signatures
• AEff
• Execute traversal method body
• B
• Visitor method declarations (including the
  default method combine(..))
• BID
• Visitor method signatures (or the built-in
  semantics, for the combine(..))
• BEff
• Execute the visitor methods and compute and
  combine the values and provide the runtime
  control over the traversal
• META

Taken apart
23
Conclusions

• The Modelling Framework by Masuhara/Kiczales
  nicely captures the different AO mechanisms
  worked on by the Demeter team.