Towards a second generation Topic Maps engine

TMRA 2008: Towards a second generation Topic Maps engine2008-10-17

1 of 27Xuân Baldauf <xuan--tm4j2--2008--tmra.de@baldauf.org>, Robert Amor <trebor@cs.auckland.ac.nz>

Towards a second generation Topic Maps Engine

Overview

technical talk

API design

multiple layers

event handling

merging done slowly or fastly

Objectives

need a Java TM engine

with TMDM supportsemantically

syntactically (names of methods match TMDM)

with instant merging

with dynamic (reversable) merging

with support for modern Java 1.5 features (generics, etc.)

which can act as backend for TM4J1 applications

with persistence support

develop a new backend for TM4J

„TMDM“ backend

is layered

is (currently) RAM-only

can do topic merging fast

Layers

layer ≈ coverage of all TMDM item types under a particular concern

separation of concerns: do one thing, and do it well

modularity of architecture:replace a layer implementationby another layer implementation

Layers

layer ≈ set of classes and interfaces in one Java package

communication between layers bymethod calls

event listeners (later)

Layers

which?

one layer for accessing a topic map

one layer for just reading a topic map

one layer for storing a topic map

one layer for merging a topic map

one layer for compatibility with TM4J1

TMDM read-write interfaces layerConcern: accessing a topic map

set of interfaces in package org.tm4j.topicmap.tmdm:

TopicMap extends ReifiableTopic extends TopicMapConstructTopicName extends ScopeableVariant extends ScopeableOccurrence extends ScopeableAssociation extends ScopeableAssociationRole extends ReifiableScopeable extends ReifiableScopeReifiable extends TopicMapConstructTopicMapConstruct

Example: AssociationRolepublic interface AssociationRole extends Reifiable, ReadableAssociationRole { public ReadableTopic getType();

public ReadableTopic getPlayer();

public Association getParent();

public void setType(Topic type);

public void setPlayer(Topic player);}

note: no setter for parent.

TMDM read-only interfaces layerConcern: just reading a topic map

set of interfaces in package org.tm4j.topicmap.tmdm:

ReadableTopicMapReadableTopicReadableTopicNameReadableVariantReadableOccurrenceReadableAssociationReadableAssociationRoleReadableScopeableReadableScopeReadableReifiableReadableTopicMapConstruct

Example: ReadableOccurencepublic interface ReadableOccurrence extends ReadableScopeable { public ReadableTopic getType(); public Locator getDatatype(); public String getValue(); public ReadableTopic getParent();}

TMDM Basic implementation layer

Concern: storing a topic map

set of classes in package org.tm4j.topicmap.tmdm.basic:

BasicTopicMapBasicTopicBasicTopicNameBasicVariantBasicOccurrenceBasicAssociationBasicAssociationRoleBasicScopeableBasicScopeBasicReifiableBasicTopicMapConstruct

Example: BasicAssociationpublic class BasicAssociation extends BasicScopeable implements Association { BasicTopicMap parent; BasicTopic type; Set<BasicAssociationRole> toles;

protected BasicAssociation(BasicTopicMap parent, BasicTopic type,BasicScope scope)

public BasicTopicMap getParent()

public void setType(Topic type) public void setType(BasicTopic type) public BasicTopic getType()

public BasicAssociationRole createRole(Topic type,Topic player) public BasicAssociationRole createRole(BasicTopic type, BasicTopic player) public Set<BasicAssociationRole> getRoles()}

TMDM Merged implementation layer

Concern: merging a topic map

set of classes in package org.tm4j.topicmap.tmdm.merged:

MergedTopicMapMergedTopicMergedTopicNameMergedVariantMergedOccurrenceMergedAssociationMergedAssociationRoleMergedScopeableMergedScopeMergedReifiableMergedTopicMapConstructMergedTopicMapView

MergedTopicMapConstructpublic abstract class MergedTopicMapConstruct<I extends ReadableTopicMapConstruct> extends TMDMObject implements ReadableTopicMapConstruct { protected List<I> components; protected MergedTopicMapView container;

protected MergedTopicMapConstruct(MergedTopicMapView container) protected MergedTopicMapConstruct(MergedTopicMapView container,I firstComponent)

protected MergedTopicMapView getContainer()

public boolean containsComponent(I component) protected void addComponent(I component) protected void removeComponent(I component) public Collection<I> getComponents() public I getRandomComponent()

public Set<Locator> getItemIdentifiers() protected Collection<Set<Locator>> getItemIdentifiersSetCollection() public Set<Locator> getItemIdentifiersSet() public Collection<Locator> getItemIdentifiersCollection() protected boolean containsItemIdentifier(Locator itemIdentifier)}

Example: MergedAssociationRolepublic class MergedAssociationRole extends MergedReifiable<ReadableAssociationRole,MergedAssociationRoleKey> implements ReadableAssociationRole {

protected MergedAssociationRole(MergedTopicMapView container, MergedAssociationRoleKey key, ReadableAssociationRole firstComponent) { super(container,key,firstComponent); }

public MergedTopic getType() { return getContainer().getMergedTopic(getRandomComponent().getType()); }

public MergedTopic getPlayer() { return getContainer().getMergedTopic(getRandomComponent().getPlayer()); }

public MergedAssociation getParent() { return getContainer().getMergedAssociation(getRandomComponent().getParent()); }}

TM4J1 compatibility layer

Concern: exposing a TMDM layer topic map using the TM4J1 API

set of classes in package org.tm4j.topicmap.tmdm.tm4j1:

TopicMapImplTopicImplBaseNameImplVariantImplOccurrenceImplAssociationImplMemberImplScopedObjectImplTopicMapObjectImpl

Wrap around TMDM to provide TM4J1 (=XTM1) semantics

TopicMapObjectImplpublic abstract class TopicMapObjectImpl< I extends org.tm4j.topicmap.tmdm.TopicMapConstruct, V extends org.tm4j.topicmap.tmdm.ReadableTopicMapConstruct> implements org.tm4j.topicmap.TopicMapObject {

protected I representedObject; protected TopicMapImpl container;}

Event Handling

Basic idea: make event firing just a method call

all event parameters are method call parameters

default implementation: empty method

Rationale

keep it small and simple

(let the JVM) optimize away unnecessary method calls

TopicMapEventListenerpublic interface TopicMapEventListener<TM extends ReadableTopicMap, T extends ReadableTopic, A extends ReadableAssociation, O extends ReadableOccurrence, TMC extends ReadableTopicMapConstruct, TN extends ReadableTopicName, V extends ReadableVariant, AR extends ReadableAssociationRole> { public void notifyTopicCreated(TM topicMap,T topic); public void notifyTopicRemoved(TM topicMap,T topic);

public void notifySubjectIdentifierAdded (TM topicMap,T topic,Locator sid); public void notifySubjectIdentifierRemoved(TM topicMap,T topic,Locator sid); public void notifySubjectLocatorAdded (TM topicMap,T topic,Locator sid); public void notifySubjectLocatorRemoved (TM topicMap,T topic,Locator sid);

public void notifyItemIdentifierAdded (TM topicMap,TMC topicMapConstruct, Locator itemIdentifier) throws DuplicateItemIdentifierException; public void notifyItemIdentifierRemoved (TM topicMap,TMC topicMapConstruct, Locator itemIdentifier);}

Peculiarities

Scope is a first-class class

replace the set of all themes by a pointer

# of distinct scopes is small, thus

# of distinct Scope objects is small

Bigger pictureTM4J1 compatibility layer

Basic layer

Merged layer

TopicMapEventListener

TopicImpl

BasicTopic

MergedTopic

representedObject

TopicMapImpl

BasicTopicMap

MergedTopicMap

representedObject

components

container container

MergedTopicMapView

components

eventListener

topicToMergedTopic

parentparent

BasicTopic

containercontainer

TopicImpl

mergedTopicMap

Merging

„A merge B = C“ is slow O(n²)

„A merge B = B“ is fast O(n·log(n))

if A is smaller than B

Merging Benchmark

0 40000 80000 120000

458,97

825,49

processing time

# TopicMapConstructs

ds “memory” backend“TMDM” backend (no merging optimization)“TMDM” backend (with merging optimization)

What to do?

instantaneous unmerging

computationally expensive

Should we support it? What to do if not?

implement some methods

autogenerate engine (Domain Specific Languages)

late merging vs. early merging

Thank you

Questions?

Towards a second generation Topic Maps engine

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