MOIN Event Framework

November 2007

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MOIN Event Framework

Event Framework - What is it? Sends events when model instances change Sends events upon partition based incidents (e.g. sync)

Key Benefit: Performance Avoids polling for model changes Avoids “diff” calculations of model state

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MOIN Event Framework

Use Case Scenarios Model Editing Tools

Tools need to update UI for changed elements Tool can refresh the UI upon changes in partitions (e.g. sync)

Model Transformation Re-Transformation only needed for changed source elements (Basis for incremental

builds)

OCL Impact Analysis Impact analysis uses events to determine minimum set of constraints to be checked

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MOIN Event Framework - Classification

Event Classification Model Change Events

Notify about elements and links

Partition Events Notify about changes of partitions Partition events do NOT carry information about the CONTENT of the partition

ChangeEvent

ModelChangeEvent PartitionChangeEvent

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Model Change Events Element Life-time

ElementCreateEvent ElementDeleteEvent

Element State AttributeValueChangeEvent Events for attributes with cardinality greater than 1

– AttributeValueAddEvent– AttributeValueRemoveEvent

Link Life-time LinkAddEvent LinkRemoveEvent

MOIN Event Framework - Classification

CEO-Name = “Henning”

CEO-Name = “Leo”

Board-Names:“Hasso”

“Henning”“Leo”

Board-Names:“Henning”

“Leo”

Hasso

ExecutiveBoard

SupervisoryBoard

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MOIN Event Framework - Classification

Model Change Events

ElementChangeEvent

ModelChangeEvent

AttributeValueEvent ElementLifeCycleEvent

AttributeMultiValueEventAttributeValueChangeEvent ElementCreateEvent ElementDeleteEvent

AttributeValueAddEventAttributeValueRemoveEvent

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MOIN Event Framework - Classification

Partition Events PartitionCreateEvent PartitionContentChangeEvent

Raised after a “save” or “sync” operation Indicates potential changes in the content of a

partition PartitionDeleteEvent PartitionSaveEvent

PartitionChangeEvent

ChangeEvent

PartitionCreateEvent PartitionContentChangeEvent ParitionDeleteEvent PartitionSaveEvent PartitionPropertyChangeEvent

PartitionPropertyChangeEvent Raised after “check-out”, “check-in”, “sync-to-

revision” Supported properties

– WRITABLE_STATE– CAN_BE_CHECKED_OUT– VERSION– VERSIONED_STATE

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MOIN Event Framework - Registration

Client Side Event Notification Implement interface “UpdateListener”

void notifyUpdate(EventChain events)

Obtain event registry connection.getEventRegistry()

Register listener and provide event filter (see next slide) registry.registerUpdateListener(listener, filter)

The implementation of notifyUpdate() will be called after completion of each Command executed in the Connection’s Session (connection.getSession())

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MOIN Event Framework - Registration

Deregistration of event listeners Obtain event registry

connection.getEventRegistry()

Deregister listener registry.deregister(listener)

Listeners are automatically deregistered on “connection.close()”

Event registration participates in the CommandStack’s “undo/redo” handling

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MOIN Event Framework - Filtering

Event Filtering Assumption:

Event listeners need a small specific subset of all available events

Brute Force Approach:Listeners receive all events and ignore the irrelevant ones

Multiple event listeners might need similar subsets Event filtering code will be performed by every listener

MOIN Approach:Proactive event filtering by the framework

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MOIN Event Framework - Filtering

Event Filtering Framework Listeners specify the needed events via the “Event Filter Language” Basic elements of the “Event Filter Language” (See JavaDoc for details)

“Global” filters– EventTypeFilter– ContainerFilter– ConnectionFilter– SessionFilter– PartitionFilter

Element related filters (ModelChangeEvents)– InstanceFilter– CompositionHierarchyFilter– ClassFilter– AttributeFilter– PackageFilter– AssociationFilter

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MOIN Event Framework - Filtering

Event Filtering Framework Basic elements can be composed powerful filter expressions via

OR operation (2 or more operands allowed) AND operation (2 or more operands allowed) NOT operation

Examples I want to be notified about the creation of instances of type MyClassEventTypeFilter(ElementCreateEvent) AND ClassFilter(MyClass)

I want to get notified when a new link of type MyAssoc is created which affects the instance MyInstanceEventTypeFilter(LinkAddEvent) AND AssociationFilter(MyAssoc) AND InstanceFilter(MyInstance)

I want to receive all EventsEventTypeFilter(ChangeEvent)

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MOIN Event Framework - Filtering

Client Side Usage of Event Filters

Create filter ("ElementChange" OR "LinkChange")

filterElementChange = new EventTypeFilter(ElementChangeEvent.class);

filterLinkChange = new EventTypeFilter(LinkChangeEvent.class);

mainFilter = new OrFilter(filterElementChange, filterLinkChange);

Register filter

eventRegistry.registerListener(mainFilter, listener);

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Thank you!