{"bundle_type":"pith_open_graph_bundle","bundle_version":"1.0","pith_number":"pith:2018:5WURPFG4WNL4UFBIPFFWC7VI3O","short_pith_number":"pith:5WURPFG4","canonical_record":{"source":{"id":"1805.03869","kind":"arxiv","version":1},"metadata":{"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.CV","submitted_at":"2018-05-10T07:53:26Z","cross_cats_sorted":[],"title_canon_sha256":"be1b7825ebed94b025c69f96555a6a369a28428603e6b76161117550b1dde480","abstract_canon_sha256":"741b65b1ad4313c117b2594b067908682651d2a584c89f5c37fdff993e65d4f4"},"schema_version":"1.0"},"canonical_sha256":"eda91794dcb357ca1428794b617ea8dba5b0fa739ae53e4b70fae33deac44123","source":{"kind":"arxiv","id":"1805.03869","version":1},"source_aliases":[{"alias_kind":"arxiv","alias_value":"1805.03869","created_at":"2026-05-18T00:16:16Z"},{"alias_kind":"arxiv_version","alias_value":"1805.03869v1","created_at":"2026-05-18T00:16:16Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.1805.03869","created_at":"2026-05-18T00:16:16Z"},{"alias_kind":"pith_short_12","alias_value":"5WURPFG4WNL4","created_at":"2026-05-18T12:32:08Z"},{"alias_kind":"pith_short_16","alias_value":"5WURPFG4WNL4UFBI","created_at":"2026-05-18T12:32:08Z"},{"alias_kind":"pith_short_8","alias_value":"5WURPFG4","created_at":"2026-05-18T12:32:08Z"}],"events":[{"event_type":"record_created","subject_pith_number":"pith:2018:5WURPFG4WNL4UFBIPFFWC7VI3O","target":"record","payload":{"canonical_record":{"source":{"id":"1805.03869","kind":"arxiv","version":1},"metadata":{"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.CV","submitted_at":"2018-05-10T07:53:26Z","cross_cats_sorted":[],"title_canon_sha256":"be1b7825ebed94b025c69f96555a6a369a28428603e6b76161117550b1dde480","abstract_canon_sha256":"741b65b1ad4313c117b2594b067908682651d2a584c89f5c37fdff993e65d4f4"},"schema_version":"1.0"},"canonical_sha256":"eda91794dcb357ca1428794b617ea8dba5b0fa739ae53e4b70fae33deac44123","receipt":{"kind":"pith_receipt","key_id":"pith-v1-2026-05","algorithm":"ed25519","signed_at":"2026-05-18T00:16:16.521254Z","signature_b64":"XLVvuB0HA+wyQB6xR6JMAVStN2UE4r2QuGB6CXe+WlNokFlIUCpC8FIGOMWHhd/He5o0AJudB0E/zNBhNikAAQ==","signed_message":"canonical_sha256_bytes","builder_version":"pith-number-builder-2026-05-17-v1","receipt_version":"0.3","canonical_sha256":"eda91794dcb357ca1428794b617ea8dba5b0fa739ae53e4b70fae33deac44123","last_reissued_at":"2026-05-18T00:16:16.520626Z","signature_status":"signed_v1","first_computed_at":"2026-05-18T00:16:16.520626Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"source_kind":"arxiv","source_id":"1805.03869","source_version":1,"attestation_state":"computed"},"signer":{"signer_id":"pith.science","signer_type":"pith_registry","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"created_at":"2026-05-18T00:16:16Z","supersedes":[],"prev_event":null,"signature":{"signature_status":"signed_v1","algorithm":"ed25519","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signature_b64":"rNPnvR59gnNvqszE9zuz6y54SSTnapRT15rUlAY3AZsD5RZqt9y6I5CGW8aKuoXQQuMolwZNkkEfaMdLU4D0Ag==","signed_message":"open_graph_event_sha256_bytes","signed_at":"2026-05-23T11:40:21.410136Z"},"content_sha256":"f1dc79db30dbe896b01f4cd9359dfbfc771c4d133b21f20bfa57ba40f427c146","schema_version":"1.0","event_id":"sha256:f1dc79db30dbe896b01f4cd9359dfbfc771c4d133b21f20bfa57ba40f427c146"},{"event_type":"graph_snapshot","subject_pith_number":"pith:2018:5WURPFG4WNL4UFBIPFFWC7VI3O","target":"graph","payload":{"graph_snapshot":{"paper":{"title":"Deep Covariance Descriptors for Facial Expression Recognition","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"cs.CV","authors_text":"Anis Kacem, Lahoucine Ballihi, Mohamed Daoudi, Naima Otberdout, Stefano Berretti","submitted_at":"2018-05-10T07:53:26Z","abstract_excerpt":"In this paper, covariance matrices are exploited to encode the deep convolutional neural networks (DCNN) features for facial expression recognition. The space geometry of the covariance matrices is that of Symmetric Positive Definite (SPD) matrices. By performing the classification of the facial expressions using Gaussian kernel on SPD manifold, we show that the covariance descriptors computed on DCNN features are more efficient than the standard classification with fully connected layers and softmax. By implementing our approach using the VGG-face and ExpNet architectures with extensive exper"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1805.03869","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"},"verdict_id":null},"signer":{"signer_id":"pith.science","signer_type":"pith_registry","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"created_at":"2026-05-18T00:16:16Z","supersedes":[],"prev_event":null,"signature":{"signature_status":"signed_v1","algorithm":"ed25519","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signature_b64":"QMIx2qKWArbdighM9hLmStNMNWMznaChFrVZJyWfpGn2zsR1k3VvdINGMw8hwA/sULjSePY/LB3oMIYTNMooCA==","signed_message":"open_graph_event_sha256_bytes","signed_at":"2026-05-23T11:40:21.410923Z"},"content_sha256":"df969abed41585f93dfabae5028ee208a5b67d23804bb83e6d5e2ebae97ec6ff","schema_version":"1.0","event_id":"sha256:df969abed41585f93dfabae5028ee208a5b67d23804bb83e6d5e2ebae97ec6ff"}],"timestamp_proofs":[],"mirror_hints":[{"mirror_type":"https","name":"Pith Resolver","base_url":"https://pith.science","bundle_url":"https://pith.science/pith/5WURPFG4WNL4UFBIPFFWC7VI3O/bundle.json","state_url":"https://pith.science/pith/5WURPFG4WNL4UFBIPFFWC7VI3O/state.json","well_known_bundle_url":"https://pith.science/.well-known/pith/5WURPFG4WNL4UFBIPFFWC7VI3O/bundle.json","status":"primary"}],"public_keys":[{"key_id":"pith-v1-2026-05","algorithm":"ed25519","format":"raw","public_key_b64":"stVStoiQhXFxp4s2pdzPNoqVNBMojDU/fJ2db5S3CbM=","public_key_hex":"b2d552b68890857171a78b36a5dccf368a953413288c353f7c9d9d6f94b709b3","fingerprint_sha256_b32_first128bits":"RVFV5Z2OI2J3ZUO7ERDEBCYNKS","fingerprint_sha256_hex":"8d4b5ee74e4693bcd1df2446408b0d54","rotates_at":null,"url":"https://pith.science/pith-signing-key.json","notes":"Pith uses this Ed25519 key to sign canonical record SHA-256 digests. Verify with: ed25519_verify(public_key, message=canonical_sha256_bytes, signature=base64decode(signature_b64))."}],"merge_version":"pith-open-graph-merge-v1","built_at":"2026-05-23T11:40:21Z","links":{"resolver":"https://pith.science/pith/5WURPFG4WNL4UFBIPFFWC7VI3O","bundle":"https://pith.science/pith/5WURPFG4WNL4UFBIPFFWC7VI3O/bundle.json","state":"https://pith.science/pith/5WURPFG4WNL4UFBIPFFWC7VI3O/state.json","well_known_bundle":"https://pith.science/.well-known/pith/5WURPFG4WNL4UFBIPFFWC7VI3O/bundle.json"},"state":{"state_type":"pith_open_graph_state","state_version":"1.0","pith_number":"pith:2018:5WURPFG4WNL4UFBIPFFWC7VI3O","merge_version":"pith-open-graph-merge-v1","event_count":2,"valid_event_count":2,"invalid_event_count":0,"equivocation_count":0,"current":{"canonical_record":{"metadata":{"abstract_canon_sha256":"741b65b1ad4313c117b2594b067908682651d2a584c89f5c37fdff993e65d4f4","cross_cats_sorted":[],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.CV","submitted_at":"2018-05-10T07:53:26Z","title_canon_sha256":"be1b7825ebed94b025c69f96555a6a369a28428603e6b76161117550b1dde480"},"schema_version":"1.0","source":{"id":"1805.03869","kind":"arxiv","version":1}},"source_aliases":[{"alias_kind":"arxiv","alias_value":"1805.03869","created_at":"2026-05-18T00:16:16Z"},{"alias_kind":"arxiv_version","alias_value":"1805.03869v1","created_at":"2026-05-18T00:16:16Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.1805.03869","created_at":"2026-05-18T00:16:16Z"},{"alias_kind":"pith_short_12","alias_value":"5WURPFG4WNL4","created_at":"2026-05-18T12:32:08Z"},{"alias_kind":"pith_short_16","alias_value":"5WURPFG4WNL4UFBI","created_at":"2026-05-18T12:32:08Z"},{"alias_kind":"pith_short_8","alias_value":"5WURPFG4","created_at":"2026-05-18T12:32:08Z"}],"graph_snapshots":[{"event_id":"sha256:df969abed41585f93dfabae5028ee208a5b67d23804bb83e6d5e2ebae97ec6ff","target":"graph","created_at":"2026-05-18T00:16:16Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"graph_snapshot":{"author_claims":{"count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","strong_count":0},"builder_version":"pith-number-builder-2026-05-17-v1","claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"paper":{"abstract_excerpt":"In this paper, covariance matrices are exploited to encode the deep convolutional neural networks (DCNN) features for facial expression recognition. The space geometry of the covariance matrices is that of Symmetric Positive Definite (SPD) matrices. By performing the classification of the facial expressions using Gaussian kernel on SPD manifold, we show that the covariance descriptors computed on DCNN features are more efficient than the standard classification with fully connected layers and softmax. By implementing our approach using the VGG-face and ExpNet architectures with extensive exper","authors_text":"Anis Kacem, Lahoucine Ballihi, Mohamed Daoudi, Naima Otberdout, Stefano Berretti","cross_cats":[],"headline":"","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.CV","submitted_at":"2018-05-10T07:53:26Z","title":"Deep Covariance Descriptors for Facial Expression Recognition"},"references":{"count":0,"internal_anchors":0,"resolved_work":0,"sample":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1805.03869","kind":"arxiv","version":1},"verdict":{"created_at":null,"id":null,"model_set":{},"one_line_summary":"","pipeline_version":null,"pith_extraction_headline":"","strongest_claim":"","weakest_assumption":""}},"verdict_id":null}}],"author_attestations":[],"timestamp_anchors":[],"storage_attestations":[],"citation_signatures":[],"replication_records":[],"corrections":[],"mirror_hints":[],"record_created":{"event_id":"sha256:f1dc79db30dbe896b01f4cd9359dfbfc771c4d133b21f20bfa57ba40f427c146","target":"record","created_at":"2026-05-18T00:16:16Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"attestation_state":"computed","canonical_record":{"metadata":{"abstract_canon_sha256":"741b65b1ad4313c117b2594b067908682651d2a584c89f5c37fdff993e65d4f4","cross_cats_sorted":[],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cs.CV","submitted_at":"2018-05-10T07:53:26Z","title_canon_sha256":"be1b7825ebed94b025c69f96555a6a369a28428603e6b76161117550b1dde480"},"schema_version":"1.0","source":{"id":"1805.03869","kind":"arxiv","version":1}},"canonical_sha256":"eda91794dcb357ca1428794b617ea8dba5b0fa739ae53e4b70fae33deac44123","receipt":{"algorithm":"ed25519","builder_version":"pith-number-builder-2026-05-17-v1","canonical_sha256":"eda91794dcb357ca1428794b617ea8dba5b0fa739ae53e4b70fae33deac44123","first_computed_at":"2026-05-18T00:16:16.520626Z","key_id":"pith-v1-2026-05","kind":"pith_receipt","last_reissued_at":"2026-05-18T00:16:16.520626Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","receipt_version":"0.3","signature_b64":"XLVvuB0HA+wyQB6xR6JMAVStN2UE4r2QuGB6CXe+WlNokFlIUCpC8FIGOMWHhd/He5o0AJudB0E/zNBhNikAAQ==","signature_status":"signed_v1","signed_at":"2026-05-18T00:16:16.521254Z","signed_message":"canonical_sha256_bytes"},"source_id":"1805.03869","source_kind":"arxiv","source_version":1}}},"equivocations":[],"invalid_events":[],"applied_event_ids":["sha256:f1dc79db30dbe896b01f4cd9359dfbfc771c4d133b21f20bfa57ba40f427c146","sha256:df969abed41585f93dfabae5028ee208a5b67d23804bb83e6d5e2ebae97ec6ff"],"state_sha256":"e13a02127cea24d00288769ce4867509212b5270f2fe0d4bd5a394b0effa26c4"},"bundle_signature":{"signature_status":"signed_v1","algorithm":"ed25519","key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signature_b64":"74zb1oW2Pkykr+qxUhxrr4UHVgIa6YRzC5lbzqhkDrwQtlDPzRQPOlc9ExcCujnfNTSoCVt57M58yLMU8TWuCg==","signed_message":"bundle_sha256_bytes","signed_at":"2026-05-23T11:40:21.414769Z","bundle_sha256":"38c8a5b6890185e1d6be3a1ed11145f771cb6a1d92b6e115765caab73eeab55c"}}