doc: trd: storage architecture

doc/reference/trd-storage.md

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+Application Persistent Data Storage and Permissions
+===================================================
+
+**TRD:** <br/>
+**Working Group:** Kernel<br/>
+**Type:** Documentary<br/>
+**Status:** Draft <br/>
+**Author:** Brad Campbell<br/>
+**Draft-Created:** 2024/03/19<br/>
+**Draft-Modified:** 2024/03/19<br/>
+**Draft-Version:** 1<br/>
+**Draft-Discuss:** [email protected]<br/>
+
+Abstract
+-------------------------------
+
+This document is in full compliance with
+[TRD1][TRD1].
+
+1 Introduction
+-------------------------------
+
+Tock applications need to be able to store persistent state. Additionally,
+applications need to be able to keep data private from other applications. The
+kernel should also be able to allow specific applications to read and modify
+state from other applications.
+
+This requires a method for assigning applications persistent identifiers,
+a mechanism for granting storage permissions to specific applications,
+and kernel abstractions for implementing storage capsules that respect
+the storage permissions.
+
+
+
+
+2 Scope
+-------------------------------
+
+This document only describes the permission architecture in Tock for supporting
+application persistent storage. This document does not include specific types of
+persistent storage (e.g., flash, FRAM, etc.) or storage access abstractions
+(e.g., block-access, byte-access, etc.).
+
+
+
+3 Assumptions
+-------------------------------
+
+All persistent application data is labeled based on the application which wrote
+the data. Applications can always read and modify data they wrote. Applications
+can read and modify data from other applications with suitable permissions.
+
+There are three types of permissions:
+
+
+1. **Write**: The application can write data.
+1. **Read**: The application can read other applications' data.
+1. **Modify**: The application can modify other applications' data.
+
+
+
+
+3 Requirements
+-------------------------------
+
+
+1. Applications are given separate write, read, and modify permissions.
+
+
+
+
+
+
+12 Authors' Addresses
+===============================
+```
+Brad Campbell <[email protected]>
+```
+
+[TRD1]: trd1-trds.md "Tock Reference Document (TRD) Structure and Keywords"