架构优化

docs/CORE_GUIDE.md

@@ -100,8 +100,11 @@ static_assert(Property::writable);
 static_assert(Property::runtime_copy_writable);
 using Value = Property::value_type;
 using Accessor = Property::accessor_type;
+using Dependencies = Property::dependency_spec;
 ```
 
+Every custom `Property_Accessor` must declare `using dependency_spec = ...`. Use `No_Property_Dependencies` when it has no dependencies; there is no implicit fallback.
+
 A `read_only` field reports:
 
 ```cpp
@@ -513,7 +516,7 @@ computed_property<Device, int>(depends_on<&Device::min_speed, &Device::max_speed
 }, key<"speed_span">)
 ```
 
-`depends_on<...>` makes dependencies explicit Schema facts. `depends_on_keys<"a", "b">` is available when key-based declaration is more appropriate. A computed view can read only its declared direct dependencies.
+`depends_on<...>` makes dependencies explicit Schema facts. `depends_on_keys<"a", "b">` is available when key-based declaration is more appropriate. `depends_on<>` is a valid explicit zero-dependency declaration. A computed view can read only its declared direct dependencies.
 
 Writable dependencies that must form one snapshot should share a synchronization domain with each other:
 
@@ -526,7 +529,9 @@ synchronization(
 
 Do not put the computed property itself in a synchronization rule. Its read slot is derived from the dependency graph; a schema or per-instance topology is rejected when synchronized dependencies do not resolve to one domain. Read-only stored dependencies need no lock slot.
 
-`schema_property_dependency_indices<Schema, Index>()` exposes the direct dependency indices for schema consumers.
+`schema_property_dependency_indices<Schema, Index>()` exposes the direct dependency indices for schema consumers. `schema_dependency_graph_acyclic<Schema>()` exposes the DAG invariant; `object_schema(...)` rejects cyclic dependency graphs at compile time.
+
+A descriptor stores Attributes and Constraints in one metadata tuple. `for_each_metadata()` traverses both kinds, `for_each_attribute()` traverses only Attributes, and `for_each_constraint()` traverses only Constraints.
 
 ## 21. Trusted accessor properties
 

docs/CORE_GUIDE.zh-CN.md

@@ -98,8 +98,11 @@ static_assert(Property::writable);
 static_assert(Property::runtime_copy_writable);
 using Value = Property::value_type;
 using Accessor = Property::accessor_type;
+using Dependencies = Property::dependency_spec;
 ```
 
+所有自定义 `Property_Accessor` 都必须显式声明 `using dependency_spec = ...`。无依赖时使用 `No_Property_Dependencies`，不再存在隐式 fallback。
+
 `read_only` 字段：
 
 ```cpp
@@ -505,7 +508,7 @@ computed_property<Device, int>(depends_on<&Device::min_speed, &Device::max_speed
 }, key<"speed_span">)
 ```
 
-`depends_on<...>` 把 dependency 变成 Schema 的显式结构事实。也可以通过 `depends_on_keys<"a", "b">` 按 key 声明。Computed view 只能读取已声明的直接 dependency。
+`depends_on<...>` 把 dependency 变成 Schema 的显式结构事实。也可以通过 `depends_on_keys<"a", "b">` 按 key 声明。`depends_on<>` 是合法的显式零依赖声明。Computed view 只能读取已声明的直接 dependency。
 
 如果 writable dependency 需要同一快照，只需要让这些 writable dependency 共享 synchronization domain：
 
@@ -518,7 +521,9 @@ synchronization(
 
 Computed Property 自身不要加入 synchronization rule。它的读取 slot 根据 dependency graph 自动推导；如果需要同步的 dependency 不在同一个 domain，Schema/实例 synchronization topology 会被拒绝。Read-only stored dependency 不需要 lock slot。
 
-Schema 可通过 `schema_property_dependency_indices<Schema, Index>()` 读取某个 Property 的直接 dependency index。
+Schema 可通过 `schema_property_dependency_indices<Schema, Index>()` 读取某个 Property 的直接 dependency index；`schema_dependency_graph_acyclic<Schema>()` 暴露 DAG invariant，`object_schema(...)` 会在编译期拒绝 dependency cycle。
+
+Descriptor 使用一份 metadata tuple 同时保存 Attribute 与 Constraint。`for_each_metadata()` 遍历两者，`for_each_attribute()` 只遍历 Attribute，`for_each_constraint()` 只遍历 Constraint。
 
 ## 21. Trusted Accessor Property
 

docs/DESIGN.md

@@ -46,6 +46,7 @@ Structive has two architectural layers.
 - intrinsic readable/writable capability;
 - Attributes;
 - Constraints;
+- dependency graph;
 - default synchronization description.
 
 This information belongs to the type.
@@ -213,7 +214,7 @@ A computed property may itself be read-only while depending on writable fields.
 
 The computed property does not contain writable storage. However, its read may require a stable snapshot of mutable dependencies.
 
-Dependencies must be explicit Schema facts. The `Synchronized_Computed_Accessor` read view can access only declared direct dependencies, and the computed property's read slot is derived from the dependency graph instead of requiring its key to be repeated in a synchronization group.
+Dependencies must be explicit Schema facts. Every Property Accessor declares a `dependency_spec`; no-dependency accessors use `No_Property_Dependencies` explicitly. The `Synchronized_Computed_Accessor` read view can access only declared direct dependencies, and the computed property's read slot is derived from the dependency graph instead of requiring its key to be repeated in a synchronization group. The dependency graph is a DAG invariant and cycles are rejected at compile time when the Schema is formed.
 
 Writable dependencies that require one atomic snapshot must share one synchronization domain with each other. Read-only stored dependencies are safe to read directly through the synchronized view because they have no managed writer.
 
@@ -221,17 +222,17 @@ Writable dependencies that require one atomic snapshot must share one synchroniz
 
 Do not give a read-only stored field a mutex. A computed read uses synchronization only for mutable dependencies that require consistency.
 
-## 12. One Attribute protocol
+## 12. One property metadata store
 
-Core and extensions share one Attribute mechanism.
+A Property Descriptor has one metadata store. Its entries are either Attributes or Constraints.
 
-An Attribute owns a category and may define whether it is single-valued and inheritable.
+Core and extensions share one Attribute mechanism for descriptive metadata. An Attribute owns a category and declares whether it is single-valued and inheritable. Constraints use the validation protocol but live in the same descriptor metadata store.
 
-Core must not create parallel metadata systems for UI, serialization, diagnostics or domain-specific features.
+Core must not create parallel metadata storage systems for UI, serialization, diagnostics or domain-specific features.
 
 ### Rule
 
-New metadata domains should extend the Attribute protocol instead of adding a second metadata framework.
+New descriptive metadata domains should extend the Attribute protocol; new validation rules should extend the Constraint protocol. Both remain entries in the same Property metadata store.
 
 ## 13. Category ownership must be clear
 

docs/DESIGN.zh-CN.md

@@ -46,6 +46,7 @@ Structive 有两层架构。
 - intrinsic readable/writable；
 - Attribute；
 - Constraint；
+- dependency graph；
 - 默认 synchronization 描述。
 
 这些属于类型。
@@ -211,7 +212,7 @@ Computed Property 自身可以只读，但它可能依赖可写字段。
 
 Computed value 本身没有可写存储，但读取它时可能需要 mutable dependency 的一致快照。
 
-Dependency 必须显式进入 Schema。`Synchronized_Computed_Accessor` 的 read view 只能读取声明过的直接 dependency，computed property 的读取 slot 从 dependency graph 推导，而不是由调用方再次把 computed key 写进 synchronization group。
+Dependency 必须显式进入 Schema。每个 Property Accessor 都必须声明 `dependency_spec`，无依赖 Accessor 显式使用 `No_Property_Dependencies`。`Synchronized_Computed_Accessor` 的 read view 只能读取声明过的直接 dependency，computed property 的读取 slot 从 dependency graph 推导，而不是由调用方再次把 computed key 写进 synchronization group。Dependency graph 是 DAG invariant，Schema 形成时在编译期拒绝 cycle。
 
 需要原子一致性的 writable dependency 应彼此处于同一个同步域。Read-only stored dependency 没有 managed writer，所以可以直接读取而无需锁。
 
@@ -219,17 +220,17 @@ Dependency 必须显式进入 Schema。`Synchronized_Computed_Accessor` 的 read
 
 不要给 read-only stored field 创建 mutex。Computed read 的同步只服务于需要一致性的 mutable dependency。
 
-## 12. 只有一套 Attribute 协议
+## 12. 只有一份 Property Metadata Storage
 
-Core 与 Extension 共用同一套 Attribute mechanism。
+Property Descriptor 只有一份 metadata storage，其中的条目只能是 Attribute 或 Constraint。
 
-Attribute 拥有 category，并可以声明 single-valued 与 inheritable 语义。
+Core 与 Extension 的描述性 metadata 共用 Attribute mechanism。Attribute 拥有 category，并声明 single-valued 与 inheritable 语义；Constraint 使用 validation protocol，但与 Attribute 保存在同一份 descriptor metadata storage 中。
 
-UI、serialization、诊断等新领域不应该另起第二套 metadata system。
+UI、serialization、诊断等新领域不应该另起第二套 metadata storage。
 
 ### 原则
 
-新的 metadata domain 应扩展 Attribute protocol，而不是创造另一套框架。
+新的描述性 metadata 扩展 Attribute protocol，新的校验规则扩展 Constraint protocol；两者都作为同一份 Property metadata 的条目存在。
 
 ## 13. Category 必须有明确所有者