Delegation of Intent via Conversation David E. Ellis

The two types of Actors Delegate

Actor Exchange Actions Collection of Communication Action is a Conversation

Actors characteristics Participants are capable of independent actions to achieve goals. They have volition and can parse various types of interactions with other participants either directly or via the delegates representing a participant. Computational Delegates are limited to specific actions to achieve goals entrusted from participants. They have no volition and can parse only specific types of interactions with either participants and/or other delegates. Interaction between computational delegates is a special type of communication action because the range of actions is limited to the mutually understood orchestration or choreography of exchanged messages. A Conversation is the sequence of communication action which leads to the joint achievement of the Real World Effect which may or may not satisfy the goals of all participants.

Delegate Definition An interactive delegate is a computational entity (e.g. application) which is orchestrated by adopting behavior it’s represented participant (usually the service consumer) An adaptive delegate is a computational entity which adopts specific behavior with respect to using a resource from some other delegates perspective only during the period of a specific service engagement (usually the service mediator or initial computational entity offering a composite service capability) A semi-autonomous delegate is a computational entity which considers the SOA eco-system and adopts behavior requested from other delegates based on it’s internal processes (usually the service provider capability offering or a sensing system in event notification MEP)

Interactive Delegate Adaptive Delegate Semi-Autonomous Delegate (Service) Service Consumer Service Mediator Service Provider Mediator Assertion Service Assertion User Interaction Rules Each Delegate has aspects of the three characteristics above: however, There is a dominate characteristic which labels the Delegate type.

Trust among delegates Stewardship is a concept of acceptance of the responsibility for honoring the original resource owner intent when using a shared informational resource (service message, consumer identity, non-repudiation.) Ownership boundary transition involves exchange of stewardship for resource between two or more Social Structures Trust is the degree of assurance that the accepting delegate shall execute the sharing of resource stewardship across ownership boundaries of social structure. The chain of trust is the aggregation of how a resource will be treated as the resource transition stewardship through respective delegates to accomplish a specific service engagement.

Delegates have two types of interfaces There are two types of interfaces used by delegates. They are Asynchronous and Synchronous. Synchronous interfaces are established by delegates to wait for a specific response for a limited timeout period. – They exhibit blocking behavior during timeout period on the requesting delegate. – They are usually associated with: Interactive delegates, or highly orchestrated semi-autonomous delegates (ESBs). Asynchronous interfaces are established by delegates to wait for a less specific communications with no timeout period. – They do not exhibit blocking behavior on the listening delegate. – They are usually associated with: Choreographed adaptive or semi-autonomous delegates They are often used by communications stacks to accept messages (.e.g. Service interface) Both types of interfaces are used in SOA ecosystems.

General Message Exchange Consumer delegate expresses intent via conversation to delegate interface via message(s) – Adaptive delegate could be Event notification (Pub/Sub) mediator or Composite Service with one or more semi-Autonomous delegates which it mediates. – Semi-Autonomous delegate (simple request/response) Delegate performs and/or observes some type of service action. Service Actions could include: – Observing immediate state of delegate (Eco-System) – Performing one or more action itself – Request other delegates to perform service actions – Waiting for another delegate to report event of interest to consumer. Delegate reports RWE and/or other information to Consumer delegate via conversation. – Report message could be single response message (request response MEP) to synchronous interface (S) of consumer (tightly coupled). – Report conversation could be series of messages during performance of service actions. This could be synchronous (S) and asynchronous (A) interface on the Consumer delegate. – Report message could be single event notification message to synchronous (s) interface of the Consumer delegate.

Message Exchange Pattern A A A S The Request Response and Event Notification MEPs are a subset of a general Consumer to Composite Service message pattern. Where: The registerinterest message is a loosely coupled requestMsg with the Event Broker and the Consumer delegate has a persistent asynchronous listener interface. In the MEP Figure: Messages 1 and 2 relay the intent of the Consumer delegate. Operations 3 and Message 4 performs or observes the actual RWE which has happened. Message 5 and 6 inform the consumer of the actual RWE which might not be the intent. A

Goals Objectives Responsibilities Constraints 1 Goals Objectives Responsibilities Constraints 2 Requires -understanding -identity 1 2 Ownership Domain 2 12 Accountability Ownership Domain 1 Intent 23 Accountability Ownership Domain 2 Intent Ownership Domain 3 Goals Objectives Responsibilities Constraints 1 Scalable SOA System of Systems Each SOA Conversation exchanges Resources which have a Purpose (Goals/needs) and Policy (Objectives, Responsibilities and Constraints). This exchange sends Intent and returns acceptance of Accountability to enforce purpose and policy of exchange. Each Resource (e.g. identity, non-repudiation, Credit Card number) exchanged in each conversation must be Atomic and Stateless. The subsequent Conversations are a composite of these original resources delegation of Goals, Objectives, Responsibility, and Constraints with the intervening Delegates Goals, Objectives, Responsibility and Constraints from their Domains. Requires -understanding -identity 1 2

Unmet Consumer NeedsUndesired Service RWE Intersection of Service(s) RWE with desired Consumers RWE (Goals/Needs) Each Intent conversation could lead to unattainable needs of requestor because of limited capability of delegate. This is even more pronounced in Composite Services.

Actor Role in Message Exchange Delegate

Actor (Role) Producer (speaker) Interactive delegate (application) Actor (Role) Consumer (Listener) Semi- autonomous delegate Adaptive delegate (e.g. SPOR) A C T D Adaptive delegate (e.g. SPOR) D T C A Semi- autonomous delegate Social Structure ASocial Structure B Policy Enforcement Point COI B Ownership Boundary Intermediate Execution Context Policy Enforcement Point COI A Ownership Boundary Intermediate Execution Context Mediator Network Delegation of Authority To Mediation Network Policy Enforcement Authority Vector for Other Stakeholders Execution Context for Mediated or Composite SOA Messaging