flatbuffers: Add component architecture

BUILD

@@ -91,6 +91,10 @@ docs(
             "mount_at": "baselibs/components/utils",
         },
     ],
+    code_targets = [
+        "//score/flatbuffers/bazel:starlark_rule_links",
+        "//score/flatbuffers:flatbufferutils",
+    ],
     external_needs = [
         "@score_platform//:needs_json_file",
         "@score_process_description//:needs_json_file",

score/flatbuffers/bazel/BUILD

@@ -53,3 +53,9 @@ py_test(
     ],
     deps = [":schema_generator_lib"],
 )
+
+filegroup(
+    name = "starlark_rule_links",
+    srcs = [":codegen.bzl"],
+    visibility = ["//visibility:public"],
+)

score/flatbuffers/bazel/codegen.bzl

@@ -136,6 +136,8 @@ generate_cpp = rule(
             doc = "Automatically included buffer_version.fbs for common buffer version support.",
         ),
     },
+
+    # req-Id: logic_arc_int_op__flatbuffers__generatedcode
     doc = """Generates a C++ header file from a FlatBuffer schema (.fbs) file.
 
     This rule uses the flatc compiler from the @flatbuffers repository with

score/flatbuffers/docs/architecture/index.rst

@@ -13,14 +13,206 @@
    # *******************************************************************************
 
 FlatBuffers Component Architecture
-==================================
+##################################
 
-.. To be created. Link from comp_req to comp is mandatory for score metamodel check.
+.. document:: FlatBuffers Architecture
+   :id: doc__flatbuffers_architecture
+   :status: valid
+   :version: 1
+   :safety: ASIL_B
+   :security: NO
+   :realizes: wp__component_arch
+
+Overview
+********
+
+The component wraps the upstream Google FlatBuffers library. Code and binary buffers are generated from
+``.fbs`` schemas via the bundled ``flatc`` Bazel rules.
+Primary use case: loading module configuration, see :need:`doc__flatbuffers` for the full component description.
+
+
+Requirements Linked to Component Architecture
+*********************************************
+
+.. needtable:: Overview of Component Requirements
+   :style: table
+   :columns: title;id
+   :filter: search("comp__baselibs_flatbuffers", str(satisfied_by))
+   :colwidths: 70,30
+
+Description
+***********
+
+FlatBuffers provides three entry points — :need:`logic_arc_int_op__flatbuffers__loadbuffer`,
+:need:`logic_arc_int_op__flatbuffers__versionreader`, and
+:need:`logic_arc_int_op__flatbuffers__generatedcode` per supported language.
+C++ and Rust are (targeting) ASIL-B implementations. Python follows the same three-entry-point architecture
+as a supportive (QM) implementation, other languages may be added on demand.
+
+Design Decisions:
+=================
+
+C++ Interface - Upstream Implementation Exposure
+-------------------------------------------------
+
+.. dec_rec:: C++ Interface - Upstream Implementation Exposure
+   :id: dec_rec__flatbuffers__upstream_impl_exposure
+   :context: C++ interface - upstream flatbuffers types exposed to consumers
+   :decision: use flatc
+   :status: accepted
+   :version: 1
+
+Use ``flatc`` for C++ code generation and the ``flatbufferscpp`` Bazel target as the
+sanctioned C++ interface for FlatBuffers consumers, with direct upstream primitives discouraged.
+
+Context
+^^^^^^^
+The component must expose FlatBuffers to C++ consumers in an ASIL-B-capable manner.
+The ``flatc`` compiler generates builder, verifier, and accessor header code from ``.fbs`` schemas.
+Generated code depends on runtime types (``flatbuffers::Table``, ``flatbuffers::Verifier``,
+``flatbuffers::Vector<>``, etc.) from the upstream library, making that dependency unavoidable.
+
+Consequences
+^^^^^^^^^^^^
+-  ``flatbufferscpp`` is a mandatory, visible compile-time dependency for all generated-code consumers.
+-  The sanctioned usage path is: verify via ``VerifyXxxBuffer()``; access data via generated accessors,
+   ``GetRoot<>()``, and keyed table-vector methods such as ``LookupByKey()``; construct via ``FlatBufferBuilder`` 
+   and ``CreateXxx()`` / ``XxxBuilder`` helpers.
+-  Bypassing generated helpers (``StartTable()``, ``AddElement()``, ``EndTable()``, custom
+   allocators) is discouraged — incorrect sequencing leads to invalid buffers or undefined behavior.
+
+Alternatives Considered
+^^^^^^^^^^^^^^^^^^^^^^^
+
+Custom flatc-like code generator
+""""""""""""""""""""""""""""""""
+Develop a bespoke code generator that wraps FlatBuffers internals and exposes only a
+project-internal API, hiding upstream ``flatbuffers::*`` types from consumers.
+
+Advantages:
+
+-  Cleaner API boundary: Consumers not exposed to upstream types.
+-  Controlled surface: Only explicitly approved operations visible to integrators.
+
+Disadvantages:
+
+-  Correctness risk: A custom generator introduces an untested translation layer between schema intent and generated code.
+-  Schema coverage uncertainty: The upstream schema language evolves, a custom generator may
+   silently mishandle schema constructs it does not support, producing incorrect or incomplete code
+   without any diagnostic.
+-  Loss of community support: ``flatc`` benefits from broad industrial adoption
+   and a community test suite that directly validates generated-code correctness.
+
+Justification for the Decision
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+The ``flatc`` generator carries established qualification evidence through broad industrial
+adoption and a comprehensive test suite that validates generated-code correctness. Treating
+direct usage of upstream primitives as a documented discouraged pattern achieves equivalent API discipline
+through process controls.
+
+Design Constraints:
+===================
+
+``Verify*`` functions validate structural well-formedness only — payload integrity is outside scope :need:`aou_req__flatbuffers__data_integrity`. 
+The same applies to file access control :need:`aou_req__flatbuffers__access_control`.
+
+Rationale Behind Architecture Decomposition
+*******************************************
+
+The component is not split into sub-components. The three key interface entry points are:
+
+- :need:`logic_arc_int_op__flatbuffers__loadbuffer`: raw file I/O, decoupled from any FlatBuffers specifics
+- :need:`logic_arc_int_op__flatbuffers__versionreader`: lightweight opt-in version check, without requiring the full application schema
+- :need:`logic_arc_int_op__flatbuffers__generatedcode`: schema-typed access layer (reader, verifier, builder)
+
+Static Architecture
+*******************
 
 .. comp:: FlatBuffers
    :id: comp__baselibs_flatbuffers
    :security: YES
    :safety:  ASIL_B
    :status: valid
    :version: 1
+   :implements: logic_arc_int__baselibs__flatbuffers[version==1]
    :belongs_to: feat__baselibs[version==1]
+
+.. comp_arc_sta:: FlatBuffers Static View
+   :id: comp_arc_sta__baselibs__flatbuffers
+   :security: YES
+   :safety: ASIL_B
+   :status: valid
+   :version: 1
+   :belongs_to: comp__baselibs_flatbuffers
+   :fulfils:
+      comp_req__flatbuffers__serialization[version==1],
+      comp_req__flatbuffers__access[version==1],
+      comp_req__flatbuffers__verification[version==1],
+      comp_req__flatbuffers__buffer_identification[version==1],
+      comp_req__flatbuffers__version_check[version==1],
+      comp_req__flatbuffers__asil[version==1]
+
+   .. needarch::
+      :scale: 50
+      :align: center
+
+      {{ draw_component(need(), needs) }}
+
+Dynamic Architecture
+********************
+
+.. comp_arc_dyn:: FlatBuffers Dynamic View
+   :id: comp_arc_dyn__baselibs__flatbuffers
+   :security: YES
+   :safety: ASIL_B
+   :status: valid
+   :version: 1
+   :belongs_to: comp__baselibs_flatbuffers
+   :fulfils:
+      comp_req__flatbuffers__serialization[version==1],
+      comp_req__flatbuffers__access[version==1],
+      comp_req__flatbuffers__verification[version==1],
+      comp_req__flatbuffers__buffer_identification[version==1],
+      comp_req__flatbuffers__version_check[version==1],
+      comp_req__flatbuffers__asil[version==1]
+
+   Put here a sequence diagram
+
+Interfaces
+**********
+
+.. logic_arc_int_op:: LoadBuffer
+   :id: logic_arc_int_op__flatbuffers__loadbuffer
+   :security: YES
+   :safety:  ASIL_B
+   :status: valid
+   :version: 1
+   :included_by: logic_arc_int__baselibs__flatbuffers[version==1]
+
+   | C++: see source_code_link ``*.hpp``
+   | Rust: not yet available
+   | Python (QM): not yet available
+
+.. logic_arc_int_op:: VersionReader
+   :id: logic_arc_int_op__flatbuffers__versionreader
+   :security: YES
+   :safety:  ASIL_B
+   :status: valid
+   :version: 1
+   :included_by: logic_arc_int__baselibs__flatbuffers[version==1]
+
+   | C++: see source_code_link ``*.hpp``
+   | Rust: not yet available
+   | Python (QM): not yet available
+
+.. logic_arc_int_op:: GeneratedCode
+   :id: logic_arc_int_op__flatbuffers__generatedcode
+   :security: YES
+   :safety:  ASIL_B
+   :status: valid
+   :version: 1
+   :included_by: logic_arc_int__baselibs__flatbuffers[version==1]
+
+   | C++: see source_code_link starlark rule ``generate_cpp``
+   | Rust: not yet available
+   | Python (QM): not yet available

score/flatbuffers/i_version_reader.hpp

@@ -27,6 +27,7 @@ namespace score
 {
 namespace flatbuffers
 {
+// # req-Id: logic_arc_int_op__flatbuffers__versionreader
 
 /// @brief Abstract interface for reading and verifying the version information
 ///        embedded in a FlatBuffer that follows the common buffer

score/flatbuffers/load_buffer.hpp

@@ -29,6 +29,7 @@ namespace score
 
 namespace flatbuffers
 {
+// # req-Id: logic_arc_int_op__flatbuffers__loadbuffer
 
 /// @brief Loads the entire contents of a binary file into a
 /// `std::vector<uint8_t>`.

score/flatbuffers/version_reader.hpp

@@ -20,6 +20,7 @@ namespace score
 {
 namespace flatbuffers
 {
+// # req-Id: logic_arc_int_op__flatbuffers__versionreader
 
 /// @brief Default implementation of `IVersionReader`.
 ///