A separate process that interacts with the external environment on behalf of the infrastructure.

Control Stream

A stream that is set up by the infrastructure for the purpose of managing infrastructure control communication associated with a particular session.

Entry Point

API that is used by external processes to control the infrastructure and communicate with agents using the infrastructure


Any messages that have been sent will be delivered to their respective destinations before the flush completes


External process that interacts with the infrastructure through the entry-point API


The components that collectively provides the mechanisms for communication, and API's for plugins, agents and the frontend. This excludes agents and junctions.


Self contained filter that operates on messages passing through the infrastructure between the entry-point and the agents.


Drain the network links of all in-flight messages related to a stream. The stream remains in a blocked state until the reverse operation.

Service Agent

An agent provided by the infrastructure for infrastructure-specific activities. Activities related to sessions and streams are managed by session agents.

Service Stream

The initial stream formed during STCI bootstrapping used to control the deployment of STCI components.


A session is created by the infrastructure in response to a request from the front-end for the purpose of running an experiment. The session comprises:

  • A resource allocation
  • Zero or more streams
  • A set of available agents and junctions
  • State information

The session is where authentication credentials are presented

Session Agent

An agent provided by the infrastructure for managing services related to a tool session. This will be things like managing junctions, handling messages, etc.

Security model

The security model determines how access to a distributed set of resouces that may have their own security model is controlled. It specifies how user authentication and the privilege levels of subsystems are managed.


An instantiation of a topology that is used for communication between the front-end and agents. Properties of a stream include:

  • A stream has one root and many leaves
  • The root can be a front-end or an agent
  • The leaves are agents
  • The root and leaves are connected in some way specified by a topology
  • Agents and front-end instances must be explicitly identified
  • Agents must be mapped to specific locations before creating a stream
  • The front-end and agents can be connected to multiple streams
  • The creator of the stream is the root of the stream
  • Agents are notified when they are added to a stream


Disconnect from agents, free any junction state, clean up stream resources, discard any messages


A tool is a collection of front-ends, junctions, and tool agents that perform a specific purpose. These components are not part of the infrastructure and must be supplied separately by the tool vendor.

Tool Agent

An agent that is provided by the tool to carry out tool-specific activities.


Defines how a front-end, junctions and agents are connected together


Restore the stream to a normal operating state after a quiesce operation.

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