{
  "id": "bst",
  "name": "Behavior Sequence Transformer",
  "description": "Alibaba 2019 BST — user behavior sequence + target item → item embeddings + positional encoding → Transformer encoder → concat with user/context → MLP → CTR",
  "icon": "🧾",
  "category": "Recommendation",
  "components": [
    { "id": "in-seq", "type": "input", "name": "Behavior Seq (T items)", "position": { "x": 80, "y": 60 }, "params": { "shape": [50] }, "inputs": [], "outputs": [] },
    { "id": "seq-emb", "type": "embedding", "name": "Item Embed", "scope": "seq_tower", "position": { "x": 80, "y": 200 }, "params": { "vocabSize": 1000000, "embeddingDim": 64 }, "inputs": [], "outputs": [] },
    { "id": "pos", "type": "positionalEncoding", "name": "Pos Encoding", "scope": "seq_tower", "position": { "x": 80, "y": 340 }, "params": { "dModel": 64, "maxLen": 50 }, "inputs": [], "outputs": [] },

    { "id": "in-tgt", "type": "input", "name": "Target Item", "position": { "x": 360, "y": 60 }, "params": { "shape": [1] }, "inputs": [], "outputs": [] },
    { "id": "tgt-emb", "type": "embedding", "name": "Target Embed", "scope": "tgt_tower", "position": { "x": 360, "y": 200 }, "params": { "vocabSize": 1000000, "embeddingDim": 64 }, "inputs": [], "outputs": [] },

    { "id": "cat-seq", "type": "concatenate", "name": "[seq; tgt]", "scope": "seq_tower", "position": { "x": 220, "y": 460 }, "params": { "dim": 0, "numInputs": 2 }, "inputs": [], "outputs": [] },

    { "id": "trf", "type": "transformerBlock", "name": "Transformer Encoder", "scope": "seq_tower", "position": { "x": 220, "y": 580 }, "params": { "dModel": 64, "numHeads": 8, "dFf": 256, "numLayers": 1, "causal": false }, "inputs": [], "outputs": [] },
    { "id": "trf-swap", "type": "permute", "name": "to_channels", "scope": "seq_tower", "position": { "x": 220, "y": 640 }, "params": { "dims": [1, 0] }, "inputs": [], "outputs": [] },
    { "id": "trf-pool", "type": "globalAvgPool1d", "name": "Mean Pool", "scope": "seq_tower", "position": { "x": 220, "y": 700 }, "params": {}, "inputs": [], "outputs": [] },

    { "id": "in-user", "type": "input", "name": "User Profile", "position": { "x": 540, "y": 60 }, "params": { "shape": [16] }, "inputs": [], "outputs": [] },
    { "id": "user-fc", "type": "linear", "name": "User Tower", "scope": "user_tower", "position": { "x": 540, "y": 200 }, "params": { "inFeatures": 16, "outFeatures": 32 }, "inputs": [], "outputs": [] },

    { "id": "cat-final", "type": "concatenate", "name": "Concat all", "scope": "mlp", "position": { "x": 320, "y": 820 }, "params": { "dim": -1, "numInputs": 2 }, "inputs": [], "outputs": [] },

    { "id": "mlp1", "type": "linear", "name": "MLP 1024", "scope": "mlp", "position": { "x": 320, "y": 940 }, "params": { "inFeatures": 96, "outFeatures": 1024 }, "inputs": [], "outputs": [] },
    { "id": "act1", "type": "prelu", "name": "PReLU", "scope": "mlp", "position": { "x": 320, "y": 1040 }, "params": {}, "inputs": [], "outputs": [] },
    { "id": "mlp2", "type": "linear", "name": "MLP 512", "scope": "mlp", "position": { "x": 320, "y": 1140 }, "params": { "inFeatures": 1024, "outFeatures": 512 }, "inputs": [], "outputs": [] },
    { "id": "act2", "type": "prelu", "name": "PReLU", "scope": "mlp", "position": { "x": 320, "y": 1240 }, "params": {}, "inputs": [], "outputs": [] },
    { "id": "mlp3", "type": "linear", "name": "MLP 256", "scope": "mlp", "position": { "x": 320, "y": 1340 }, "params": { "inFeatures": 512, "outFeatures": 256 }, "inputs": [], "outputs": [] },
    { "id": "ctr", "type": "linear", "name": "CTR Head", "scope": "mlp", "position": { "x": 320, "y": 1440 }, "params": { "inFeatures": 256, "outFeatures": 1 }, "inputs": [], "outputs": [] },
    { "id": "sig", "type": "sigmoid", "name": "Sigmoid", "scope": "mlp", "position": { "x": 320, "y": 1540 }, "params": {}, "inputs": [], "outputs": [] },
    { "id": "out", "type": "output", "name": "P(click)", "position": { "x": 320, "y": 1660 }, "params": {}, "inputs": [], "outputs": [] }
  ],
  "connections": [
    { "id": "c1", "from": "in-seq", "to": "seq-emb", "fromPort": "bottom", "toPort": "top" },
    { "id": "c2", "from": "seq-emb", "to": "pos", "fromPort": "bottom", "toPort": "top" },
    { "id": "c3", "from": "pos", "to": "cat-seq", "fromPort": "bottom", "toPort": "left" },
    { "id": "c4", "from": "in-tgt", "to": "tgt-emb", "fromPort": "bottom", "toPort": "top" },
    { "id": "c5", "from": "tgt-emb", "to": "cat-seq", "fromPort": "bottom", "toPort": "right" },
    { "id": "c6", "from": "cat-seq", "to": "trf", "fromPort": "bottom", "toPort": "top" },
    { "id": "c7", "from": "trf", "to": "trf-swap", "fromPort": "bottom", "toPort": "top" },
    { "id": "c7b", "from": "trf-swap", "to": "trf-pool", "fromPort": "bottom", "toPort": "top" },
    { "id": "c8", "from": "trf-pool", "to": "cat-final", "fromPort": "bottom", "toPort": "left" },

    { "id": "u1", "from": "in-user", "to": "user-fc", "fromPort": "bottom", "toPort": "top" },
    { "id": "u2", "from": "user-fc", "to": "cat-final", "fromPort": "bottom", "toPort": "right" },

    { "id": "m1", "from": "cat-final", "to": "mlp1", "fromPort": "bottom", "toPort": "top" },
    { "id": "m2", "from": "mlp1", "to": "act1", "fromPort": "bottom", "toPort": "top" },
    { "id": "m3", "from": "act1", "to": "mlp2", "fromPort": "bottom", "toPort": "top" },
    { "id": "m4", "from": "mlp2", "to": "act2", "fromPort": "bottom", "toPort": "top" },
    { "id": "m5", "from": "act2", "to": "mlp3", "fromPort": "bottom", "toPort": "top" },
    { "id": "m6", "from": "mlp3", "to": "ctr", "fromPort": "bottom", "toPort": "top" },
    { "id": "m7", "from": "ctr", "to": "sig", "fromPort": "bottom", "toPort": "top" },
    { "id": "m8", "from": "sig", "to": "out", "fromPort": "bottom", "toPort": "top" }
  ]
}