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# Architecture
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2022-02-24 12:25:03 +00:00
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<!--
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2022-02-10 12:36:29 +00:00
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> What is an architecture? It's the rules of the platform which are
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> true on any embodiment of it, not just the one you work on today.
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> These rules are aimed at programs (what are valid programs) and the
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> design (its invariants) both. — [Olivier
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> Giroux](https://twitter.com/__simt__/status/1489790925266059264),
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> Feb. 2022
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2022-02-24 12:25:03 +00:00
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-->
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2022-02-11 09:48:49 +00:00
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The **[Syndicated Actor Model (SAM)](./glossary.md#syndicated-actor-model)** is at the heart of
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Synit. In turn, the SAM builds upon [E-style actors](./glossary.md#e), replacing
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message-exchange with eventually-consistent *state replication* as the fundamental building
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block for interaction. Both E and the SAM are instances of the [Object Capability (ocap)
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model](./glossary.md#object-capability-model), a [compositional](./glossary.md#compositional)
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approach to system security.
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The "feel" of the system is somewhere between Smalltalk-style
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object-orientation, publish-subscribe programming, E- or Erlang-style
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actor interaction, Prolog-style logic programming, and Esterel-style
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reactive dataflow.
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1. **Programs are Actors.** Synit *programs*
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("[actors](./glossary.md#actor)" in the SAM) interoperate by
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*[dataspace](./glossary.md#dataspace)*-mediated exchange of
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*[messages](./glossary.md#message)* and replication of
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*[conversational state](./glossary.md#conversational-state)*
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expressed as *[assertions](./glossary.md#assertion)*.
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2022-02-11 10:01:57 +00:00
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2. **Ocaps for security and privacy.** The ocap model provides the fundamental building blocks
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for secure composition of programs in the system. Synit extends the core ocap model with
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[Macaroon](./glossary.md#macaroon)-inspired *[attenuation](./glossary.md#attenuation)* of
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capabilities, for both limiting visibility of state and constraining access to behaviour.
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3. **Reactivity and homeostasis.** Programs publish relevant aspects of their internal state
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to peers (usually by placing [assertions](./glossary.md#assertion) in a dataspace). Peers
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[subscribe](./glossary.md#observe) to those assertions, reacting to changes in state to
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preserve overall system equilibrium.
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3. **Heterogeneous; "open".** Different programming languages and styles interoperate freely.
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Programs may or may not be structured internally using SAM principles: the system as a
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whole is where the architectural principles are applied. However, it often makes good sense
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to use SAM principles *within* a given Synit program as well as *between* programs.
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4. **Language-neutral.** Where possible, programs interoperate via a
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simple [protocol](./protocol.md) across transports like TCP/IP,
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WebSockets, and Unix sockets and pipes. Otherwise, they
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interoperate using traditional Unix techniques. The concrete
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syntax for the messages and assertions exchanged among programs is
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the [Preserves](./guide/preserves.md) data language.
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5. **Strongly typed.** Preserves [Schemas](./guide/preserves.md#schemas)
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describe the data exchanged among programs. Schemas compile to
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type definitions in various programming languages, helping give an
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ergonomic development experience as well as ensuring safety at
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runtime.
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