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Neochiron An Architecture Assembly Language. ADL Constructs. Architecture description language provides primitives for composing an architecture Components, connectors, ports, roles Components and connectors are composite primitives are high level
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ADL Constructs • Architecture description language • provides primitives for composing an architecture • Components, connectors, ports, roles • Components and connectors are composite • primitives are high level • Need lower level abstractions to compose components and connectors • is a high level specification language • Need lower level language for implementation • support specific styles • Need to support different styles through a common sub-language • Need for a simple set of lower level primitives to define architectural constructs
The C2 Architectural Style • Asynchronous, event-based communication among autonomous components, mediated by active connectors • Minimal component interdependencies • no component-component links • separation of computation from communication • implicit invocation via connectors • substrate independence • Event-flow rules: • Hierarchical application Connector “pull” Notifications fall Component Requests rise “push” Connector
C2-StyleComposition and Interaction A B C D E
Authorized User Authorized User Verify User Information Accept Login Event Window Opened Window Closed Concrete Example:User Authentication User Repository Main Window Login Dialog Graphics Toolkit
Internal Architecture of a Component InternalObject
Neochiron • Neochiron is an assembly language for C2-style architectures • Approach • Provide low-level primitives to assemble C2 components and connectors • Primitives emphasize performance/monitoring • Connectors and components can be built out of other connectors and components • Transparency of architecture down to the assembly level • Fine grain control of semantics • Connectors with wide range of semantics and guarantees
Neochiron Benefits • Combines lessons from Weaves with C2-style • Performance matters • Communication semantics matters • Fine grain control matters • Realistic platform assumptions • Finite buffering • Delivery guarantees • Safe halt/restart
Elements of Neochiron • Fragment • Locus of computation • Assembly language equivalent of C2 component • Transport • Locus of communication • Assembly language equivalent of C2 connector • Portal • Message entry and exit points for fragments and transports • Locus of message filtering and fragment/transport monitoring
Elements of Neochiron (2) • Jumper • “Wire” that interconnects two portals • Key to atomic disconnect • Hierarchical assembly • A fragment or transport may be a network of other fragments and transports • Point to point networks • Fragments cannot connect to other fragments, transports cannot connect to other transports • No fragment is connected to itself in a closed loop
output portals input portals Fragments • Portals • Input portals distinguished from output portals • Animus • thread that animates the fragment • State • Run, halt, snooze, suspend • Methods • Start, Suspend, Halt (control the component) • Notify (notify the component) • Progress • Examines/classifies messages (signals, requests) • Schedules consumption of signals and requests • Request (consume a request) • Signal (consume a signal) signals/requests signals/requests
Transports • Transports move signals and requests from one place to another • Finite capacity • Pushing and pulling fragments can block • Fixed number of input/output portals • mxn transport has m input portals and n output portals • Basic transports are passive • No internal thread – motive force supplied by fragment threads • Queue_1_1 • Fixed length queue with 1 input portal and 1 output portal
Transports • Queue_1_N • Fixed length queue with 1 input portal and N output portals • Fair n-way splitter • Queue_M_1 • Fixed length queue with M input portals and 1 output portal • Fair m-way merge • Replicate_1_N • N way shallow copy of messages (1 input portal/N output portals) • Fair m-way shallow replication
jumper owner filters g0, g1, ... path = (t, c) filters f0, f1, ... jumper owner Portals and Jumpers
A C2-styled Architecture N components M components
request signal I I I I I I O O O O O O C2 Translated in Neochiron N components portals M components
request signal I I I I I I I O O O O O O O N components portals n-way replicator m-way fair merge M components
request signal I I I I I I I O O O O O O O N components portals n-way fair merge n-way replicator m-way replicator m-way fair merge M components
Modeling Problems • Representing Neochiron semantics • Linking Neochiron formally to C2 • Modeling dynamism in C2 • Modeling composite connectors such as security and multi-versioning • Creating a hierarchical model for C2 and Neochiron • Modeling ordering semantics in C2 • Testing utility of Neochiron to other architectural styles • Modeling fragment ownership of thread of control • Non-circularity of fragment connectivity