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  "current_status": "CURRENT",
  "observation_status": "SPEC_ONLY",
  "freshness": "CURRENT",
  "last_verified": "2026-10-06",
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  "superseded_by": [],
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        "EA-255-FIRST-20261006"
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  "research_sections": [
    {
      "heading": "PUBLIC_CLAIM",
      "text": "Feature StoreはGenerative AIやAgentへ低遅延のstructured contextを供給できます。ただし、`feature retrieval success`を値の最新性、point-in-time correctness、回答正しさ、または業務action権限の保証として扱いません。"
    },
    {
      "heading": "FEATURE_IDENTITY",
      "text": "少なくとも次を追跡します。\n\n\n- entity key / entity definition\n- feature name and definition/version\n- event timestamp\n- source/update provenance\n- online/offline retrieval path\n- materialization/sync state\n- backend/client/plugin version\n\n\nfeature名だけで値の意味と時間位置を再現できるとは仮定しません。"
    },
    {
      "heading": "ONLINE_OFFLINE_BOUNDARY",
      "text": "online storeは低遅延のlatest-value serving、offline storeはhistorical retrieval/training/evaluation/replayという異なる時間用途を持ちます。\n\n\nonline write成功直後にoffline historyへ同じ値が存在すると仮定しません。buffering、replication、storage type、materialization/sync条件を確認します。"
    },
    {
      "heading": "POINT_IN_TIME_CORRECTNESS",
      "text": "training、evaluation、replayでは、対象時刻より未来のfeatureを混入させないpoint-in-time joinを要求します。\n\n\n現在のlatest featureをhistorical decisionの再現に流用しません。"
    },
    {
      "heading": "FRESHNESS_AND_TTL",
      "text": "online retrievalが成功してもfreshとは限りません。\n\n\nfreshness gateでは、可能な範囲で以下を確認します。\n\n\n- event timestamp\n- last update / materialization watermark\n- configured TTL\n- runtime pathでのTTL enforcement\n- missing/null state\n\n\nTTLは設定値だけでなく、対象version/backendの実際のonline retrieval pathで効くかを検証します。"
    },
    {
      "heading": "MISSING_VALUE_POLICY",
      "text": "missing、null、expired、sync未完了を同じ状態として扱いません。\n\n\n必要featureが欠落した場合、LLMに値を推測させず、UNKNOWN、明示fallback、処理停止のいずれかをpolicyとして固定します。"
    },
    {
      "heading": "VECTOR_BOUNDARY",
      "text": "Feature Storeがembedding/vector retrievalを統合していても、vector relevanceとstructured feature correctnessを同一gateにしません。\n\n\nvector hitはentity属性、entitlement、risk score、inventory等の業務featureが正しい証明ではありません。"
    },
    {
      "heading": "AUTHORIZATION_BOUNDARY",
      "text": "Feature Store read権限とAgent/toolのbusiness-action権限を分離します。\n\n\nentitlementやpolicy関連featureを取得できることを、送金、削除、承認、外部送信等のaction authorizationの代替にしません。"
    },
    {
      "heading": "VERSION_AND_BACKEND_BOUNDARY",
      "text": "Feature Store製品名だけでruntime behaviorを固定しません。\n\n\nprovider product generation、SDK、registry、online/offline backend、plugin/connector versionを記録します。deprecated generationを現行挙動として扱いません。"
    },
    {
      "heading": "FAILURE_ENVELOPE",
      "text": "wrong entity、entity collision、feature definition drift、event-time/ingestion-time混同、future leakage、stale online value、TTL unenforced、null/default ambiguity、materialization lag/failure、sync未実行、offline persistence delay、online/offline divergence、backend ordering bug、plugin mismatch、deprecated generation、embedding drift、unauthorized disclosure、feature-read/action-auth混同、cache staleness、unit/timezone mismatch、historical delete semantics、replay provenance欠落を想定します。"
    },
    {
      "heading": "IMPLEMENTATION_STATE",
      "text": "本項は2026-10-06時点のFeast、Amazon SageMaker Feature Store、Google Vertex AI Feature Storeのcurrent public documentationと、version-bounded Feast issue evidenceに基づきます。\n\n\nlive Feature Store、backend、vector DB、LLM/Agentへのmutationや性能試験は未実施です。"
    },
    {
      "heading": "SAFE_WORDING",
      "text": "Feature StoreはGenerative AIやAgentへ低遅延のstructured contextを供給できますが、取得成功を値の最新性、point-in-time correctness、回答正しさ、または業務action権限の保証として扱わないでください。entity、feature definition/version、event time、online/offline path、materialization/sync、TTL/freshness、backend/client versionを固定し、missing/stale featureはUNKNOWNまたは明示fallbackとして処理します。vector retrievalを併用する場合も、relevanceとstructured feature correctnessを別gateにします。"
    },
    {
      "heading": "OPEN_UNKNOWN",
      "text": "organization feature store、chosen provider/product generation、entity model、feature definitions、freshness SLO、TTL enforcement、online/offline backend、materialization cadence、point-in-time join implementation、vector backend、embedding version、IAM、PII policy、retention/deletion、tenant region/quota/SLAは未確認です。"
    }
  ],
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