Connector Roles and Types II

Stream Connectors

Stream connectors provide communication services.

They are used to transfer large amounts of data between autonomous processes.

Stream Connector Dimensions

Delivery

Defines how stream data is delivered.

• Best effort
• Exactly once
• At most once
• At least once

Bounds

Defines whether the amount of data that can be transferred is limited.

• Bounded
• Unbounded

Buffering

Defines whether data is temporarily stored during transfer.

• Buffered
• Unbuffered

Throughput

Defines the amount of data processed or transferred over time.

• Atomic units
• Higher-order units

State

Defines whether the stream maintains state.

• Stateless
• Stateful

Identity

Defines whether the communicating stream has an identity.

• Named
• Unnamed

Locality

Defines where the communicating processes are located.

• Local
• Remote

Synchronicity

Defines how stream communication is synchronized.

• Synchronous
• Asynchronous
• Timeout synchronous

Format

Defines the representation of the transferred data.

• Raw
• Structured

Cardinality

Defines the number of senders and receivers.

• Multi-sender
• Multi-receiver
• Multi-sender / multi-receiver

Arbitrator Connectors

Arbitrator connectors provide both facilitation and coordination services.

They are useful when components cannot make assumptions about their state and needs.

An arbitrator can:

• Streamline system operations and resolve conflicts through facilitation.
• Redirect the flow of control through coordination.

Arbitrator Connector Dimensions

The lecture identifies several dimensions for arbitrators:

Fault Handling

Defines how failures are handled.

Examples include:

• Authoritative
• Voting
• Separative

Concurrency

Defines how concurrent activities are controlled.

Examples include:

• Monitor
• Lock
• Light
• Heavy

Transactions

Defines how transaction-related behavior is handled.

Important aspects include:

• Awareness Whether transaction information is considered.
• Isolation How independently transactions operate.

Security

Defines how access and protection are controlled.

Includes:

• Authentication Verifying identity.
• Authorization Determining permitted access.
• Privacy Protecting information.
• Integrity Ensuring information remains correct.
• Durability Preserving information over time.

Scheduling

Defines how activities are scheduled.

Important factors include:

• Time
• Weight

Adaptor Connectors

Adaptor connectors facilitate interaction between components that were not designed to interoperate.

They provide conversion services.

Types of Conversion

Invocation Conversion

Converts one invocation mechanism into another.

Examples:

• Address mapping
• Marshalling
• Translation

Packaging Conversion

Changes how components or data are packaged.

Examples:

• Wrappers
• Packagers

Protocol Conversion

Converts one communication protocol into another.

Presentation Conversion

Converts the way information is presented between interacting components.

Distributor Connectors

Distributor connectors provide facilitation services.

They:

1. Identify interaction paths.
2. Route communication through those paths.
3. Coordinate components along the paths.

Distributor Connector Dimensions

Naming

Defines how interaction paths or destinations are identified.

Naming can be:

• Structure-based
  • Hierarchical
  • Flat
• Attribute-based

Distributor Delivery

Defines how communication is delivered.

Delivery Semantics

• Best effort
• Exactly once
• At most once
• At least once

Delivery Mechanism

• Unicast One destination.
• Multicast Multiple selected destinations.
• Broadcast All relevant destinations.

Routing

Defines how communication paths are selected.

Membership

Defines how participants belong to the communication group.

• Bounded
• Ad-hoc

Path

Defines how the communication path is maintained.

• Static
• Cached
• Dynamic

Connector Types at a Glance