Here’s a clean **v0.1 draft for ASL-HOST**, scoped to what we discussed — minimal, environment-focused, without touching semantics or storage encoding. This is the runtime/host interface layer that bridges ASL-STORE(-INDEX) to a real system.

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# ASL-HOST v0.1 – Host/Runtime Interface for ASL Stores

## 1. Purpose

**ASL-HOST** specifies the **runtime contract** between an ASL store and the host environment.
It defines **what the host must provide** for an ASL store to operate correctly, without imposing:

* Storage semantics
* Encoding
* Policy
* Security beyond minimal integrity guarantees

It supports **POSIX filesystems, ZFS, object stores**, or other backing layers.

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## 2. Core Concepts

| Concept           | Definition                                                                |
| ----------------- | ------------------------------------------------------------------------- |
| **StoreHandle**   | Opaque reference to a host-provided store instance                        |
| **StoreLocation** | Host-defined location where a store exists (path, URI, mount point, etc.) |
| **AppendUnit**    | Minimum atomic write unit for the append-only log                         |
| **SnapshotID**    | Opaque identifier of a host-provided snapshot                             |
| **HostClock**     | Monotonic counter or timestamp source                                     |
| **HostIdentity**  | Unique machine or user identity for signing or domain minting             |

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## 3. Store Instantiation

### 3.1 Store Creation

* `CreateStore(location: StoreLocation) → StoreHandle`
* Must guarantee crash-consistent initialization.
* Location may be:

  * POSIX path
  * ZFS dataset
  * Object store bucket
* StoreHandle is **opaque**, only valid while the store exists on host.

### 3.2 Store Open

* `OpenStore(location: StoreLocation) → StoreHandle`
* Host must provide durable, consistent view.
* Opening an existing store must not corrupt previous data.

### 3.3 Store Close

* `CloseStore(store: StoreHandle)`
* Ensures all writes are persisted to durable media.
* Optional: triggers host-specific flush or checkpoint.

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## 4. Atomic Append / Log Operations

* Host must provide **atomic append** semantics.
* Minimum guarantees:

  * Sequential ordering (logseq monotonicity)
  * Crash consistency (partial writes are not visible)
* AppendUnit:

  * Defined by host; could be page-size or object-size
  * ASL-STORE must tolerate host’s granularity

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## 5. Snapshot Management

* Optional but recommended.
* Host provides:

  * `CreateSnapshot(store: StoreHandle) → SnapshotID`
  * `MountSnapshot(store: StoreHandle, id: SnapshotID) → StoreHandle`
* Guarantees:

  * Snapshot captures a consistent view of sealed blocks
  * Mounting snapshot produces read-only store handle
* Host may use:

  * ZFS snapshot
  * POSIX filesystem copy-on-write overlay
  * Object store versioning

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## 6. Durability & Crash Semantics

* Host must ensure:

  * Writes are durable after append or flush
  * Crash recovery restores store to last durable state
  * Open, unsealed blocks may be lost without breaking invariants
* StoreHandle and append-only log are **atomic units** visible to ASL-STORE

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## 7. Minimal Identity & Logging

* Host must provide:

  * `HostClock()` → monotonic timestamp / counter
  * `HostIdentity()` → machine or user ID for signing / domain minting
  * Optional log for debugging or auditing

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## 8. Error Semantics

* Operations may return:

  * `STORE_OK`
  * `STORE_EXISTS`
  * `STORE_NOT_FOUND`
  * `STORE_IO_ERROR`
  * `STORE_CONCURRENT_MODIFICATION`
* ASL-STORE must handle errors deterministically

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## 9. Security Considerations

* ASL-HOST does **not enforce cryptography**.
* Host may provide optional:

  * Encryption at rest
  * Access control
  * Secure snapshot mechanisms
* Certificates and trust are handled in **ASL-AUTH**, separate layer

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## 10. Example Implementations

| Backend          | How ASL-HOST maps                                                                  |
| ---------------- | ---------------------------------------------------------------------------------- |
| POSIX filesystem | StoreLocation = path; append = write+fsync; snapshot = overlayfs copy              |
| ZFS dataset      | StoreLocation = dataset; append = zfs sync; snapshot = zfs snapshot                |
| Object store     | StoreLocation = bucket/namespace; append = object PUT; snapshot = versioned bucket |

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## 11. Versioning

* Spec version: **0.1**
* Backward incompatible changes must bump major version.
* Minimal compliance: implement store creation/open/close and append guarantees.

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## 12. Summary

**ASL-HOST v0.1**:

* Defines **runtime contract** between ASL store and host
* Provides **store handles, atomic append, snapshots, identity**
* Layered cleanly above ASL-STORE(-INDEX), below system or OS
* Keeps **semantics, encoding, and trust separate**

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If you like, I can **draft ASL-AUTH v0.1** next, and then show how **SystemRescue could instantiate ASL-HOST with POSIX/ZFS to seed a personal domain**. That would give a complete view for your rescue scenario.

Do you want me to do that next?