diff --git a/crates/ops/apsis-schedule/src/error.rs b/crates/ops/apsis-schedule/src/error.rs
index c5090e3..43f9dab 100644
--- a/crates/ops/apsis-schedule/src/error.rs
+++ b/crates/ops/apsis-schedule/src/error.rs
@@ -3,8 +3,8 @@
 use core::fmt;
 
 /// The category of a schedule error.
-    ///
-    /// 计划错误的类别。
+///
+/// 计划错误的类别。
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 #[non_exhaustive]
 pub enum ScheduleErrorKind {
@@ -54,8 +54,8 @@ impl fmt::Display for ScheduleErrorKind {
 }
 
 /// A failure while building or evaluating a schedule.
-    ///
-    /// 构建或评估计划时发生的失败。
+///
+/// 构建或评估计划时发生的失败。
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ScheduleError {
     kind: ScheduleErrorKind,
diff --git a/crates/ops/apsis-schedule/src/placement.rs b/crates/ops/apsis-schedule/src/placement.rs
index 91cb981..a9609bf 100644
--- a/crates/ops/apsis-schedule/src/placement.rs
+++ b/crates/ops/apsis-schedule/src/placement.rs
@@ -4,21 +4,33 @@ use apsis_resource::ResourceId;
 use apsis_task::TaskId;
 
 /// One task placed on the schedule.
+///
+/// 计划上放置的一个任务。
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Placement {
     /// The task placed.
+    ///
+    /// 被放置的任务。
     pub task: TaskId,
     /// The start time of the placement, in seconds.
+    ///
+    /// 放置的起始时刻，单位为秒。
     pub start: f64,
     /// The duration of the placement, in seconds.
     ///
     /// This is copied from the task so that a schedule carries everything
     /// needed to evaluate it without the tasks to hand.
+    ///
+    /// 放置的时长，单位为秒。
+    ///
+    /// 它从任务复制而来，故一份计划无需持有任务集合也能完成评估。
     pub duration: f64,
 }
 
 impl Placement {
     /// Creates a placement.
+    ///
+    /// 创建一次放置。
     pub const fn new(task: TaskId, start: f64, duration: f64) -> Self {
         Self {
             task,
@@ -28,6 +40,8 @@ impl Placement {
     }
 
     /// Returns the end time of the placement, in seconds.
+    ///
+    /// 返回放置的结束时刻，单位为秒。
     pub fn end(&self) -> f64 {
         self.start + self.duration
     }
@@ -37,31 +51,50 @@ impl Placement {
     /// The interval is half-open, so a placement covers its start and not its
     /// end. That convention lets two back to back placements share a boundary
     /// without overlapping.
+    ///
+    /// 当该放置覆盖某瞬时返回 `true`。
+    ///
+    /// 区间是半开的，故放置含其起点而不含其终点。该约定使两个首尾相接的
+    /// 放置可共享边界而不重叠。
     pub fn covers(&self, time: f64) -> bool {
         time >= self.start && time < self.end()
     }
 
     /// Returns `true` when the placement overlaps another.
+    ///
+    /// 当该放置与另一个放置重叠时返回 `true`。
     pub fn overlaps(&self, other: &Self) -> bool {
         self.start < other.end() && other.start < self.end()
     }
 
     /// Returns `true` when the placement is usable.
+    ///
+    /// 当该放置可用时返回 `true`。
     pub fn is_valid(&self) -> bool {
         self.start.is_finite() && self.duration.is_finite() && self.duration >= 0.0
     }
 }
 
 /// How much of one resource a schedule uses.
+///
+/// 一份计划对某个资源的使用情况。
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct ResourceUsage {
     /// The resource.
+    ///
+    /// 该资源。
     pub resource: ResourceId,
     /// The greatest total demand placed on the resource at any instant.
+    ///
+    /// 该资源上任意瞬时的最大总需求。
     pub peak_demand: f64,
     /// The time during which the resource is used at all, in seconds.
+    ///
+    /// 该资源被使用的总时长，单位为秒。
     pub busy_seconds: f64,
     /// The number of placements that use the resource.
+    ///
+    /// 使用该资源的放置数量。
     pub placement_count: usize,
 }
 
@@ -73,6 +106,13 @@ impl ResourceUsage {
     /// only half occupied by demand still counts as busy.
     ///
     /// Returns `None` when the interval is not positive.
+    ///
+    /// 返回该资源在某区间上的利用率。
+    ///
+    /// 其值为忙碌时长除以区间长度。这是时间利用率而非容量利用率：仅被
+    /// 需求占据一半的资源同样算作忙碌。
+    ///
+    /// 区间非正时返回 `None`。
     pub fn utilisation(&self, interval_seconds: f64) -> Option<f64> {
         if interval_seconds > 0.0 && interval_seconds.is_finite() {
             Some(self.busy_seconds / interval_seconds)
@@ -83,19 +123,33 @@ impl ResourceUsage {
 }
 
 /// The evaluation of a whole schedule.
+///
+/// 整份计划的评估结果。
 #[derive(Debug, Clone, PartialEq)]
 pub struct Evaluation {
     /// The number of placements.
+    ///
+    /// 放置的数量。
     pub placed_count: usize,
     /// The number of tasks that were offered to the schedule.
+    ///
+    /// 提交给该计划的任务数量。
     pub offered_count: usize,
     /// The sum of the placed durations, in seconds.
+    ///
+    /// 已放置时长之和，单位为秒。
     pub scheduled_seconds: f64,
     /// The earliest start time, or zero when nothing is placed.
+    ///
+    /// 最早的开始时刻；无放置时为零。
     pub makespan_start: f64,
     /// The latest end time, or zero when nothing is placed.
+    ///
+    /// 最晚的结束时刻；无放置时为零。
     pub makespan_end: f64,
     /// The usage of each resource, in identifier order.
+    ///
+    /// 各资源的使用情况，按标识符顺序排列。
     pub resource_usage: Vec<ResourceUsage>,
 }
 
@@ -105,6 +159,10 @@ impl Evaluation {
     ///
     /// This is the time from the earliest start to the latest end, which is
     /// the makespan of the plan.
+    ///
+    /// 返回该计划覆盖的规划时域长度，单位为秒。
+    ///
+    /// 它是从最早开始到最晚结束的时间，即该计划的 makespan。
     pub fn makespan(&self) -> f64 {
         (self.makespan_end - self.makespan_start).max(0.0)
     }
@@ -112,6 +170,10 @@ impl Evaluation {
     /// Returns the fraction of the offered tasks that were placed.
     ///
     /// Returns `None` when no tasks were offered.
+    ///
+    /// 返回所提交任务中被放置的比例。
+    ///
+    /// 没有提交任务时返回 `None`。
     pub fn fill_rate(&self) -> Option<f64> {
         if self.offered_count == 0 {
             return None;
@@ -120,11 +182,15 @@ impl Evaluation {
     }
 
     /// Returns `true` when every offered task was placed.
+    ///
+    /// 当所有提交任务均被放置时返回 `true`。
     pub fn is_complete(&self) -> bool {
         self.placed_count == self.offered_count
     }
 
     /// Returns the usage of one resource.
+    ///
+    /// 返回某个资源的使用情况。
     pub fn usage_of(&self, resource: ResourceId) -> Option<&ResourceUsage> {
         self.resource_usage
             .iter()
diff --git a/crates/ops/apsis-schedule/src/schedule.rs b/crates/ops/apsis-schedule/src/schedule.rs
index 3c3d709..c75e5ea 100644
--- a/crates/ops/apsis-schedule/src/schedule.rs
+++ b/crates/ops/apsis-schedule/src/schedule.rs
@@ -13,6 +13,12 @@ use std::collections::BTreeMap;
 /// may be placed at most once: placing it again is an error rather than a
 /// silent overwrite, because a schedule that contains two placements for one
 /// task is not a schedule.
+///
+/// 一组任务放置。
+///
+/// 该计划按放置发生的顺序保存各项，并维护从任务到放置的索引，故按任务查找
+/// 是直接的。一个任务至多放置一次：重复放置是错误而非静默覆盖，因为含有
+/// 同一任务两处放置的集合已不是一份计划。
 #[derive(Debug, Clone, PartialEq, Default)]
 pub struct Schedule {
     placements: Vec<Placement>,
@@ -21,6 +27,8 @@ pub struct Schedule {
 
 impl Schedule {
     /// Creates an empty schedule.
+    ///
+    /// 创建一份空计划。
     pub fn new() -> Self {
         Self {
             placements: Vec::new(),
@@ -29,26 +37,36 @@ impl Schedule {
     }
 
     /// Returns the placements in the order they were made.
+    ///
+    /// 返回按放置顺序排列的各项。
     pub fn placements(&self) -> &[Placement] {
         &self.placements
     }
 
     /// Returns the number of placements.
+    ///
+    /// 返回放置的数量。
     pub fn len(&self) -> usize {
         self.placements.len()
     }
 
     /// Returns `true` when there are no placements.
+    ///
+    /// 当没有放置时返回 `true`。
     pub fn is_empty(&self) -> bool {
         self.placements.is_empty()
     }
 
     /// Returns `true` when a task has been placed.
+    ///
+    /// 当某任务已被放置时返回 `true`。
     pub fn is_placed(&self, task: TaskId) -> bool {
         self.index.contains_key(&task.index())
     }
 
     /// Returns the placement of a task.
+    ///
+    /// 返回某任务的放置。
     pub fn placement_of(&self, task: TaskId) -> Option<&Placement> {
         self.index
             .get(&task.index())
@@ -64,6 +82,14 @@ impl Schedule {
     ///
     /// Returns an error when the task is already placed, when the start time
     /// is not finite, or when the placement falls outside the task's window.
+    ///
+    /// 把某任务放置在某时刻。
+    ///
+    /// 放置会对照该任务的窗口校验。任务的资源通过任务本身随放置一同记录，
+    /// 故本方法无需它们；容量检查由需要资源的
+    /// [`Schedule::validate_capacity`] 完成。
+    ///
+    /// 该任务已被放置、起始时刻非有限，或放置落在任务窗口之外时返回错误。
     pub fn place(
         &mut self,
         task: &apsis_task::Task,
@@ -107,6 +133,10 @@ impl Schedule {
     /// Removes the placement of a task.
     ///
     /// Returns an error when the task is not placed.
+    ///
+    /// 移除某任务的放置。
+    ///
+    /// 该任务未被放置时返回错误。
     pub fn unplace(&mut self, task: TaskId) -> Result<Placement, ScheduleError> {
         let position = self.index.remove(&task.index()).ok_or_else(|| {
             ScheduleError::new(ScheduleErrorKind::NotPlaced).with_detail(format!("{task}"))
@@ -115,11 +145,15 @@ impl Schedule {
         // Every placement after the removed one shifts down by one, so the
         // index must be rebuilt. The schedule is small enough that this is
         // cheaper than maintaining a linked structure.
+        // 被移除项之后的每项都前移一位，故索引须重建。计划规模足够小，
+        // 这比维护链式结构更划算。
         self.rebuild_index();
         Ok(removed)
     }
 
     /// Rebuilds the task to position index.
+    ///
+    /// 重建从任务到位置的索引。
     fn rebuild_index(&mut self) {
         self.index.clear();
         for (position, placement) in self.placements.iter().enumerate() {
@@ -128,6 +162,8 @@ impl Schedule {
     }
 
     /// Returns the placements that use a resource, in time order.
+    ///
+    /// 返回使用某资源的放置，按时间排序。
     pub fn placements_on(
         &self,
         resource: ResourceId,
@@ -159,6 +195,12 @@ impl Schedule {
     /// tasks on disjoint resources may legitimately overlap, so a caller that
     /// wants to know whether a resource is overbooked should use
     /// [`Schedule::validate_capacity`] instead.
+    ///
+    /// 当两个不同任务的放置重叠时返回 `true`。
+    ///
+    /// 这是计划与自身的比较，忽略资源。位于不相交资源上的两个任务本就可
+    /// 以合法重叠，故欲知某资源是否超订的调用方应改用
+    /// [`Schedule::validate_capacity`]。
     pub fn has_overlapping_placements(&self) -> bool {
         for (index, placement) in self.placements.iter().enumerate() {
             if self.placements[..index]
@@ -172,6 +214,8 @@ impl Schedule {
     }
 
     /// Returns the total placed duration, in seconds.
+    ///
+    /// 返回已放置的总时长，单位为秒。
     pub fn scheduled_seconds(&self) -> f64 {
         self.placements
             .iter()
@@ -182,6 +226,10 @@ impl Schedule {
     /// Returns the earliest start of any placement.
     ///
     /// Returns `None` when the schedule is empty.
+    ///
+    /// 返回所有放置中最早的开始时刻。
+    ///
+    /// 计划为空时返回 `None`。
     pub fn earliest_start(&self) -> Option<f64> {
         self.placements
             .iter()
@@ -196,6 +244,10 @@ impl Schedule {
     /// Returns the latest end of any placement.
     ///
     /// Returns `None` when the schedule is empty.
+    ///
+    /// 返回所有放置中最晚的结束时刻。
+    ///
+    /// 计划为空时返回 `None`。
     pub fn latest_end(&self) -> Option<f64> {
         self.placements
             .iter()
@@ -219,6 +271,17 @@ impl Schedule {
     /// between boundaries.
     ///
     /// Returns an error describing the first violation.
+    ///
+    /// 对照一组资源校验该计划。
+    ///
+    /// 检查分两部分。其一，每处放置须与其任务的需求一致，这可捕获用另
+    /// 一份任务列表建成的计划。其二，对每个资源，任意瞬时的总需求不得超
+    /// 过容量。
+    ///
+    /// 第二部分按时间序遍历各资源的放置边界，由于相邻边界之间总需求恒定，
+    /// 该遍历是精确的。
+    ///
+    /// 返回描述首个违规的错误。
     pub fn validate_capacity(
         &self,
         tasks: &[apsis_task::Task],
@@ -243,6 +306,7 @@ impl Schedule {
 
         for resource in resources.resources() {
             // The boundaries at which the total demand can change.
+            // 总需求可能发生变化的各边界。
             let mut events: Vec<(f64, f64)> = Vec::new();
             for placement in &self.placements {
                 let Some(task) = tasks.iter().find(|task| task.id == placement.task) else {
@@ -259,6 +323,8 @@ impl Schedule {
             // Sort by time, with a release before an acquisition at the same
             // instant so that two placements that touch are not counted as
             // overlapping.
+            // 按时间排序；同一瞬先释放后获取，使两个相接的放置不被计为
+            // 重叠。
             events.sort_by(|first, second| {
                 first
                     .0
@@ -294,6 +360,11 @@ impl Schedule {
     /// The evaluation reports the counts, the makespan, and the usage of each
     /// resource. The peak demand of a resource is found by the same event
     /// sweep that the capacity check uses, so the two agree.
+    ///
+    /// 对照任务列表与资源集合评估该计划。
+    ///
+    /// 评估给出各项计数、makespan 以及每个资源的使用情况。资源的峰值
+    /// 需求由与容量检查相同的事件扫掠求得，故二者一致。
     pub fn evaluate(
         &self,
         tasks: &[apsis_task::Task],
@@ -364,6 +435,11 @@ impl Schedule {
     /// A schedule is stored in the order it was built, which is the order a
     /// scheduler considered the tasks. A caller that wants to read the plan
     /// in time order uses this.
+    ///
+    /// 返回按开始时刻排序的计划副本，原计划不变。
+    ///
+    /// 计划按其构建顺序存储，即调度器考虑任务的顺序。欲按时间阅读该计
+    /// 划的调用方使用本方法。
     pub fn in_time_order(&self) -> Vec<Placement> {
         let mut ordered = self.placements.clone();
         ordered.sort_by(|first, second| {
@@ -381,6 +457,11 @@ impl Schedule {
     ///
     /// Returns `None` when the resource is idle there. This is what a
     /// sequential scheduler asks when it looks for the next gap.
+    ///
+    /// 若某资源在给定瞬时忙碌，返回其变为空闲的时刻。
+    ///
+    /// 该资源在彼处空闲时返回 `None`。顺序调度器寻找下一个空隙时正是
+    /// 询问这一点。
     pub fn resource_busy_until(
         &self,
         resource: ResourceId,