mchades commented on code in PR #13842:
URL: https://github.com/apache/gravitino/pull/13842#discussion_r4291178870


##########
docs/semantic-models.md:
##########
@@ -0,0 +1,102 @@
+---
+title: "Semantic Models"
+slug: "/semantic-models"
+keyword: "semantic model, semantic metadata, Ossie, metrics, Gravitino"
+license: "This software is licensed under the Apache License version 2."
+---
+
+## Introduction
+
+A Semantic Model describes the business meaning of data: the datasets to use, 
their fields and
+relationships, and the metrics calculated from them. A sales model, for 
example, can give
+analytical applications and AI tools a shared definition of revenue.
+
+Semantic Models live in schemas of relational catalogs. Gravitino stores their 
definitions and
+manages their lifecycle, ownership, privileges, and tags, even when the 
underlying catalog system
+has no semantic-model feature. They are separate from [SQL 
views](./tables-and-views.md) and the
+AI/ML artifacts managed by a [model catalog](./model-catalog.md).
+
+Gravitino manages the definitions. Query compilation, execution, 
materialization, and publishing
+engine-specific semantic objects are responsibilities of the applications that 
consume them.
+
+## Quick Start
+
+**1. Choose the source data.** Connect a relational catalog and identify the 
tables or logical views
+the model will describe. See [Catalogs and Schemas](./catalogs-and-schemas.md).
+
+**2. Create or import a model.** Define datasets and metrics through REST or a 
client SDK, or import
+an Apache Ossie YAML or JSON document. The source objects must already exist.
+
+**3. Govern and share the definition.** Assign access through roles, attach 
tags, and let consumers
+load the model or export it as an Ossie document. Permission to read a 
definition does not itself
+grant access to the source data.
+
+Worked examples are in [Manage Semantic Model 
Metadata](./manage-semantic-model-metadata-using-gravitino.md).
+
+## The Semantic Model
+
+A model has a name, an optional comment, string-valued Gravitino properties, a 
structured
+definition, and audit information. The definition uses these components:
+
+| Component | Purpose |
+|-----------|---------|
+| `datasets` | A required, non-empty list of named sources. Each dataset can 
define fields, a primary key, and unique keys. |
+| `fields` | Named expressions within a dataset, with optional data types, 
labels, descriptions, and dimension information. |
+| `relationships` | Links between datasets in the same model, using source 
column names in `fromColumns` and `toColumns`. |
+| `metrics` | Named expressions such as `SUM(orders.order_amount)`, with 
optional data types and descriptions. |
+| `aiContext` | Context for consumers, represented as text or a structured 
object. |
+| `customExtensions` | Vendor-specific information preserved with the 
definition. |
+
+Expressions contain one or more dialect-specific representations. The Java and 
Python SDKs provide
+`Dialects` constants for `ANSI_SQL`, `SNOWFLAKE`, `MDX`, `TABLEAU`, 
`DATABRICKS`, `MAQL`, and `BIGQUERY`.
+Other non-empty dialect identifiers are also accepted and preserved. Choose 
identifiers supported
+by the application consuming the model. Gravitino validates the definition's 
structure but does
+not parse or execute the expression text.
+
+### Sources and Validation
+
+Dataset sources use `catalog.schema.object` within the model's metalake. They 
may reference another
+catalog or schema in that metalake. Each source must resolve to an existing 
table or a logical view
+supported by its catalog. Cross-metalake references are not supported.
+
+The `from` and `to` endpoints of a relationship name datasets within the model.
+Primary-key, unique-key, and relationship columns refer to columns of the 
source table or view,
+rather than field aliases in the model. Gravitino checks that these columns 
exist; it does not
+check whether the data satisfies the declared keys or relationships.
+
+Creating, importing, or replacing a definition checks source existence and 
these columns, even
+when authorization is disabled. With authorization enabled, source lookups 
also require the
+caller's access to the source metadata.
+
+Loading or exporting a model, renaming it, and changing only its comment or 
properties do not
+revalidate source metadata. Review definitions when their source schemas 
change: a stored model
+can become stale after a source column is changed or removed.
+
+### Exchanging Definitions
+
+The native REST API and standalone Apache Ossie documents represent the same 
definition in
+different forms:
+
+| Aspect | Native REST API | Ossie document |
+|--------|-----------------|----------------|
+| Definition location | Nested under `definition` in the model object | 
Datasets and metrics at the document root |
+| Field names | `primaryKey`, `datatype` | `primary_key`, `datatype` |

Review Comment:
   Updated the mapping table and Ossie introduction to include root-level 
`relationships`, and added the `uniqueKeys`, `fromColumns`, and `toColumns` 
field-name mappings.



##########
docs/manage-semantic-model-metadata-using-gravitino.md:
##########
@@ -0,0 +1,612 @@
+---
+title: "Manage Semantic Model Metadata"
+slug: "/manage-semantic-model-metadata-using-gravitino"
+keyword: "semantic model management, semantic metadata, Ossie, Gravitino"
+license: "This software is licensed under the Apache License version 2."
+---
+
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+## Introduction
+
+This page covers the Gravitino API for Semantic Models. For what a model 
contains, how its sources
+are validated, and how it relates to tables and views, see [Semantic 
Models](./semantic-models.md).
+For creating the catalog and schema a model lives in, see
+[Manage Catalogs and Schemas](./manage-catalogs-and-schemas.md).
+
+## Before You Start
+
+The examples use the `2.0.0-SNAPSHOT` server and clients. They assume:
+
+* A server at `http://localhost:8090` and an existing metalake named `example`.
+* A relational catalog named `sales`, with a schema named `mart`.
+* An existing source table `sales.mart.orders` with `order_id`, `customer_id`, 
and `order_amount` columns.
+* An existing source table `sales.mart.customers` with `customer_id` and 
`customer_code` columns.
+
+See [Manage Relational 
Metadata](./manage-relational-metadata-using-gravitino.md) to create the
+source tables. Add the credentials required by your deployment as described in
+[Authentication](./security/how-to-authenticate.md). With authorization 
enabled, the caller also
+needs the [model and source privileges](#ownership-and-privileges).
+
+Choose one language tab and follow its examples. Each language manages the 
same model names, so
+running create or import again in another language reports that the model 
already exists.
+Run the [drop examples](#drop-a-semantic-model) when you have finished.
+
+Java and Python model identifiers are relative to the loaded catalog 
(`schema.model`). Dataset
+sources use `catalog.schema.object` within the same metalake. For SDK 
configuration, see
+[Client Setup](./how-to-use-gravitino-client.md) and [Python 
Client](./how-to-use-python-client.md).
+
+<details>
+<summary>Java and Python client setup and imports</summary>
+
+Place the operation snippets inside the client block below. The block closes 
the client when
+finished; Java file operations also require the calling method to handle or 
declare `IOException`.
+
+<Tabs groupId='language' queryString>
+<TabItem value="java" label="Java">
+
+```java
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import org.apache.gravitino.NameIdentifier;
+import org.apache.gravitino.Namespace;
+import org.apache.gravitino.client.GravitinoClient;
+import org.apache.gravitino.semantic.DataType;
+import org.apache.gravitino.semantic.Dataset;
+import org.apache.gravitino.semantic.DialectExpression;
+import org.apache.gravitino.semantic.Dialects;
+import org.apache.gravitino.semantic.Expression;
+import org.apache.gravitino.semantic.Field;
+import org.apache.gravitino.semantic.Metric;
+import org.apache.gravitino.semantic.OssieDocument;
+import org.apache.gravitino.semantic.OssieFormat;
+import org.apache.gravitino.semantic.Relationship;
+import org.apache.gravitino.semantic.SemanticModel;
+import org.apache.gravitino.semantic.SemanticModelCatalog;
+import org.apache.gravitino.semantic.SemanticModelChange;
+import org.apache.gravitino.semantic.SemanticModelDefinition;
+
+try (GravitinoClient client = GravitinoClient.builder("http://localhost:8090";)
+    .withMetalake("example").build()) {
+  SemanticModelCatalog models = 
client.loadCatalog("sales").asSemanticModelCatalog();
+  NameIdentifier ident = NameIdentifier.of("mart", "sales_model");
+
+  // Run the Java operation examples here.
+}
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+from pathlib import Path
+
+from gravitino import GravitinoClient, NameIdentifier
+from gravitino.api.semantic.data_type import DataType
+from gravitino.api.semantic.dataset import Dataset
+from gravitino.api.semantic.dialect_expression import DialectExpression
+from gravitino.api.semantic.dialects import Dialects
+from gravitino.api.semantic.expression import Expression
+from gravitino.api.semantic.field import Field
+from gravitino.api.semantic.metric import Metric
+from gravitino.api.semantic.relationship import Relationship
+from gravitino.api.semantic.semantic_model_change import SemanticModelChange
+from gravitino.api.semantic.semantic_model_definition import 
SemanticModelDefinition
+from gravitino.namespace import Namespace
+
+client = GravitinoClient(uri="http://localhost:8090";, metalake_name="example")
+try:
+    models = client.load_catalog("sales").as_semantic_model_catalog()
+    ident = NameIdentifier.of("mart", "sales_model")
+
+    # Run the Python operation examples here.
+finally:
+    client.close()
+```
+
+</TabItem>
+</Tabs>
+
+</details>
+
+## Semantic Model Operations
+
+### Create a Semantic Model
+
+A model needs a name and a definition with at least one dataset. This example 
defines a revenue
+metric over orders and links orders to customers by `customer_id`. The native 
REST API nests the
+definition under `definition`. Its field names include `primaryKey` and 
`datatype`.
+
+The relationship's `from` and `to` name datasets in the model. Its column 
lists and the datasets'
+keys use source table column names, even when those columns are not listed in 
`fields`. Each array
+inside `uniqueKeys` defines one unique key.
+
+<Tabs groupId='language' queryString>
+<TabItem value="shell" label="REST">
+
+```shell
+curl -X POST -H "Accept: application/vnd.gravitino.v1+json" \
+  -H "Content-Type: application/json" -d '{
+  "name": "sales_model",
+  "comment": "Governed sales definitions",
+  "properties": {"domain": "sales"},
+  "definition": {
+    "datasets": [
+      {
+        "name": "orders",
+        "source": {"namespace": ["sales", "mart"], "name": "orders"},
+        "primaryKey": ["order_id"],
+        "fields": [
+          {
+            "name": "order_amount",
+            "expression": {
+              "dialects": [{"dialect": "ANSI_SQL", "expression": 
"order_amount"}]
+            },
+            "datatype": "Decimal"
+          }
+        ]
+      },
+      {
+        "name": "customers",
+        "source": {"namespace": ["sales", "mart"], "name": "customers"},
+        "primaryKey": ["customer_id"],
+        "uniqueKeys": [["customer_code"]],
+        "fields": []
+      }
+    ],
+    "relationships": [
+      {
+        "name": "orders_to_customers",
+        "from": "orders",
+        "to": "customers",
+        "fromColumns": ["customer_id"],
+        "toColumns": ["customer_id"]
+      }
+    ],
+    "metrics": [
+      {
+        "name": "total_revenue",
+        "expression": {
+          "dialects": [{"dialect": "ANSI_SQL", "expression": 
"SUM(orders.order_amount)"}]
+        },
+        "datatype": "Decimal"
+      }
+    ]
+  }
+}' 
http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models
+```
+
+</TabItem>
+<TabItem value="java" label="Java">
+
+```java
+Expression amountExpression = Expression.builder()
+    .withDialects(new DialectExpression[] {
+        DialectExpression.builder().withDialect(Dialects.ANSI_SQL)
+            .withExpression("order_amount").build()
+    }).build();
+Field amount = Field.builder().withName("order_amount")
+    .withExpression(amountExpression).withDatatype(DataType.DECIMAL).build();
+Dataset orders = Dataset.builder().withName("orders")
+    .withSource(NameIdentifier.of("sales", "mart", "orders"))
+    .withPrimaryKey(new String[] {"order_id"})
+    .withFields(new Field[] {amount}).build();
+Dataset customers = Dataset.builder().withName("customers")
+    .withSource(NameIdentifier.of("sales", "mart", "customers"))
+    .withPrimaryKey(new String[] {"customer_id"})
+    .withUniqueKeys(new String[][] {{"customer_code"}})
+    .withFields(new Field[0]).build();
+Relationship ordersToCustomers = 
Relationship.builder().withName("orders_to_customers")
+    .withFrom("orders").withTo("customers")
+    .withFromColumns(new String[] {"customer_id"})
+    .withToColumns(new String[] {"customer_id"}).build();
+
+Expression revenueExpression = Expression.builder()
+    .withDialects(new DialectExpression[] {
+        DialectExpression.builder().withDialect(Dialects.ANSI_SQL)
+            .withExpression("SUM(orders.order_amount)").build()
+    }).build();
+Metric revenue = Metric.builder().withName("total_revenue")
+    .withExpression(revenueExpression).withDatatype(DataType.DECIMAL).build();
+SemanticModelDefinition definition = SemanticModelDefinition.builder()
+    .withDatasets(new Dataset[] {orders, customers})
+    .withRelationships(new Relationship[] {ordersToCustomers})
+    .withMetrics(new Metric[] {revenue}).build();
+
+SemanticModel created = models.createSemanticModel(
+    ident, "Governed sales definitions", definition, Map.of("domain", 
"sales"));
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+amount = Field(
+    "order_amount",
+    Expression([DialectExpression(Dialects.ANSI_SQL, "order_amount")]),
+    datatype=DataType.DECIMAL)
+orders = Dataset(
+    "orders",
+    NameIdentifier.of("sales", "mart", "orders"),
+    primary_key=["order_id"],
+    fields=[amount])
+customers = Dataset(
+    "customers",
+    NameIdentifier.of("sales", "mart", "customers"),
+    primary_key=["customer_id"],
+    unique_keys=[["customer_code"]],
+    fields=[])
+orders_to_customers = Relationship(
+    "orders_to_customers",
+    from_dataset="orders",
+    to_dataset="customers",
+    from_columns=["customer_id"],
+    to_columns=["customer_id"])
+revenue = Metric(
+    "total_revenue",
+    Expression([DialectExpression(Dialects.ANSI_SQL, 
"SUM(orders.order_amount)")]),
+    datatype=DataType.DECIMAL)
+definition = SemanticModelDefinition(
+    datasets=[orders, customers],
+    relationships=[orders_to_customers],
+    metrics=[revenue])
+
+created = models.create_semantic_model(
+    ident, "Governed sales definitions", definition, {"domain": "sales"})
+```
+
+</TabItem>
+</Tabs>
+
+The REST response contains `code: 0` and a `semanticModel` object with `name`, 
`comment`,
+`properties`, `definition`, and `audit`. The SDKs return a `SemanticModel` 
directly. Creating a name
+that already exists reports a conflict without overwriting the model.
+
+### List Semantic Models
+
+Listing returns identifiers rather than complete definitions. With 
authorization enabled, it
+includes only models visible to the caller.
+
+<Tabs groupId='language' queryString>
+<TabItem value="shell" label="REST">
+
+```shell
+curl -X GET -H "Accept: application/vnd.gravitino.v1+json" \
+  
http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models
+```
+
+</TabItem>
+<TabItem value="java" label="Java">
+
+```java
+NameIdentifier[] identifiers = models.listSemanticModels(Namespace.of("mart"));
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+identifiers = models.list_semantic_models(Namespace.of("mart"))
+```
+
+</TabItem>
+</Tabs>
+
+REST identifiers include the namespace `["example", "sales", "mart"]`. SDK 
identifiers are relative
+to the loaded catalog, such as `mart.sales_model`.
+
+### Load a Semantic Model
+
+Load returns the stored definition, properties, comment, and audit information.
+
+<Tabs groupId='language' queryString>
+<TabItem value="shell" label="REST">
+
+```shell
+curl -X GET -H "Accept: application/vnd.gravitino.v1+json" \
+  
http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models/sales_model
+```
+
+</TabItem>
+<TabItem value="java" label="Java">
+
+```java
+SemanticModel loaded = models.loadSemanticModel(ident);
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+loaded = models.load_semantic_model(ident)
+```
+
+</TabItem>
+</Tabs>
+
+### Alter a Semantic Model
+
+Changes are applied in order in one request. If any change or the resulting 
model is invalid, none
+of the changes is persisted.
+
+| Change | REST update |
+|--------|-------------|
+| Rename within the schema | `{"@type":"rename","newName":"renamed_model"}` |
+| Update or clear the comment | 
`{"@type":"updateComment","newComment":"Reviewed sales definitions"}`; use 
`null` to clear it. |
+| Set a property | 
`{"@type":"setProperty","property":"domain","value":"finance"}` |
+| Remove a property | `{"@type":"removeProperty","property":"domain"}` |
+| Replace the definition | Set `@type` to `replaceDefinition` and supply the 
complete native definition in `definition`. |
+
+<Tabs groupId='language' queryString>
+<TabItem value="shell" label="REST">
+
+```shell
+curl -X PUT -H "Accept: application/vnd.gravitino.v1+json" \
+  -H "Content-Type: application/json" -d '{
+  "updates": [
+    {"@type": "updateComment", "newComment": "Reviewed sales definitions"},
+    {"@type": "setProperty", "property": "domain", "value": "finance"}
+  ]
+}' 
http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models/sales_model
+```
+
+</TabItem>
+<TabItem value="java" label="Java">
+
+```java
+SemanticModel altered = models.alterSemanticModel(
+    ident,
+    SemanticModelChange.updateComment("Reviewed sales definitions"),
+    SemanticModelChange.setProperty("domain", "finance"));
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+altered = models.alter_semantic_model(
+    ident,
+    SemanticModelChange.update_comment("Reviewed sales definitions"),
+    SemanticModelChange.set_property("domain", "finance"))
+```
+
+</TabItem>
+</Tabs>
+
+Definition replacement replaces all datasets, relationships, and metrics. 
Include everything you
+want to retain. In Java, use 
`SemanticModelChange.replaceDefinition(definition)`; in Python, use
+`SemanticModelChange.replace_definition(definition)`. Each replacement 
revalidates the complete
+definition and its source access. Comment and property changes do not 
revalidate sources.
+
+## Apache Ossie Import and Export
+
+An Ossie document uses snake_case names, string source identifiers, and 
root-level datasets and
+metrics. See [Exchanging 
Definitions](./semantic-models.md#exchanging-definitions) for the mapping
+from the native REST format.
+
+### Import a Document
+
+Save the following as `sales.ossie.yaml`. It uses a different model name so it 
can be imported
+alongside the model created above:
+
+```yaml
+version: 0.2.0.dev0
+name: imported_sales_model
+description: Imported sales definitions
+datasets:
+  - name: orders
+    source: sales.mart.orders
+    primary_key: [order_id]
+    fields:
+      - name: order_amount
+        expression:
+          dialects:
+            - dialect: ANSI_SQL
+              expression: order_amount
+        datatype: Decimal
+  - name: customers
+    source: sales.mart.customers
+    primary_key: [customer_id]
+    unique_keys: [[customer_code]]
+    fields: []
+relationships:
+  - name: orders_to_customers
+    from: orders
+    to: customers
+    from_columns: [customer_id]
+    to_columns: [customer_id]
+metrics:
+  - name: total_revenue
+    expression:
+      dialects:
+        - dialect: ANSI_SQL
+          expression: SUM(orders.order_amount)
+    datatype: Decimal
+custom_extensions:
+  - vendor_name: GRAVITINO_PROPERTIES
+    data: '{"domain":"sales"}'
+```
+
+<Tabs groupId='language' queryString>
+<TabItem value="shell" label="REST">
+
+```shell
+curl -X POST -H "Accept: application/vnd.gravitino.v1+json" \
+  -H "Content-Type: application/yaml" --data-binary @sales.ossie.yaml \
+  
http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models/ossie
+```
+
+</TabItem>
+<TabItem value="java" label="Java">
+
+```java
+SemanticModel importedModel = models.importOssieDocument(
+    Namespace.of("mart"), 
OssieDocument.yaml(Files.readString(Path.of("sales.ossie.yaml"))));
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+imported_model = models.import_ossie_document(
+    Namespace.of("mart"), Path("sales.ossie.yaml").read_text(encoding="utf-8"))
+```
+
+</TabItem>
+</Tabs>
+
+Import creates a new model using the name in the document and applies the same 
validation as
+native creation. An existing name reports a conflict. REST returns the native 
`semanticModel`
+response; the SDKs return a `SemanticModel`.
+
+Send the raw document text. For JSON, use `Content-Type: application/json` in 
REST,
+`OssieDocument.json(...)` in Java, or `document_format="json"` in Python. YAML 
requests use
+`application/yaml`; `application/x-yaml` and `text/yaml` are also accepted. An 
omitted content type
+defaults to YAML, while an unsupported content type returns `415`. Use an 
explicit content type
+with curl, since its data options otherwise send a form content type.
+
+### Export a Document
+
+Export the native model as an Ossie JSON document:
+
+<Tabs groupId='language' queryString>
+<TabItem value="shell" label="REST">
+
+```shell
+curl 
'http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models/sales_model/ossie?format=json'
 \
+  -o exported-sales.ossie.json
+```
+
+</TabItem>
+<TabItem value="java" label="Java">
+
+```java
+OssieDocument exported = models.exportOssieDocument(ident, OssieFormat.JSON);
+Files.writeString(Path.of("exported-sales.ossie.json"), exported.content());
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+exported = models.export_ossie_document(ident, document_format="json")
+Path("exported-sales.ossie.json").write_text(exported, encoding="utf-8")
+```
+
+</TabItem>
+</Tabs>
+
+For YAML, use `format=yaml` in REST, `OssieFormat.YAML` in Java, or 
`document_format="yaml"` in
+Python. REST and Python default to YAML when the format is omitted. REST 
returns the document
+text without the native response wrapper, and Python returns that text 
unchanged.
+
+The `ossie-version` model property supplies the document's `version`. Native 
creation records the
+server's default when the property is omitted; import records the document 
version. Other model
+properties are exchanged through the root `GRAVITINO_PROPERTIES` custom 
extension, whose `data`
+is a JSON object encoded as a string. Its values must be strings. Use 
`properties` when creating a
+model through the native API; the reserved extension is for Ossie exchange.
+
+## Ownership and Privileges
+
+When authorization is enabled, a model's creator becomes its owner. For 
callers using explicit
+privilege grants, access also requires `USE_CATALOG` and `USE_SCHEMA` on the 
parent objects:
+
+| Operation | Required model privilege or ownership |
+|-----------|---------------------------------------|
+| Create or import | `CREATE_SEMANTIC_MODEL` on the containing schema or an 
ancestor. |
+| Discover, load, or export | `USE_SEMANTIC_MODEL`, `MODIFY_SEMANTIC_MODEL`, 
or ownership. |
+| Alter or rename | `MODIFY_SEMANTIC_MODEL` or ownership. |
+| Drop | Ownership; `MODIFY_SEMANTIC_MODEL` alone is insufficient. |
+
+Parent owners can also operate on contained models under the
+[access-control rules](./security/access-control.md#required-privileges). A 
schema owner still
+needs access to the catalog. Create, import, and definition replacement 
additionally check the
+caller's access to every source table or view. Permission to load a Semantic 
Model does not itself
+grant permission to read its source data.
+
+Ownership and role grants use metadata object type `SEMANTIC_MODEL` and a name 
such as
+`sales.mart.sales_model` within the selected metalake. See
+[Ownership](./security/access-control.md#ownership) and the
+[access-control walkthrough](./security/access-control.md#walkthrough) to 
manage owners and roles.
+Setting a string property named `owner` does not transfer ownership.
+
+### Tags and Policies
+
+Create a tag in the metalake before attaching it to a Semantic Model. For an 
existing tag named
+`certified`, use the `semantic_model` object type in the REST path:
+
+```shell
+curl -X POST -H "Accept: application/vnd.gravitino.v1+json" \
+  -H "Content-Type: application/json" -d '{"tagsToAdd": ["certified"]}' \
+  
http://localhost:8090/api/metalakes/example/objects/semantic_model/sales.mart.sales_model/tags
+```
+
+Tag operations have their own authorization requirements. See
+[Manage Tags](./manage-tags-in-gravitino.md#object-operations) for creating, 
attaching, listing, and
+removing tags. Policies are selected through tags; see
+[Policy-to-Tag 
Associations](./manage-policies-in-gravitino.md#policy-to-tag-associations).
+
+## Drop a Semantic Model
+
+Drop the models after trying the examples. Dropping removes the semantic 
metadata and its
+governance associations without deleting source tables, views, or data.
+
+<Tabs groupId='language' queryString>
+<TabItem value="shell" label="REST">
+
+```shell
+curl -X DELETE -H "Accept: application/vnd.gravitino.v1+json" \
+  
http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models/sales_model
+curl -X DELETE -H "Accept: application/vnd.gravitino.v1+json" \
+  
http://localhost:8090/api/metalakes/example/catalogs/sales/schemas/mart/semantic-models/imported_sales_model
+```
+
+</TabItem>
+<TabItem value="java" label="Java">
+
+```java
+boolean dropped = models.dropSemanticModel(ident);
+boolean importedDropped = models.dropSemanticModel(
+    NameIdentifier.of("mart", "imported_sales_model"));
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+
+```python
+dropped = models.drop_semantic_model(ident)
+imported_dropped = models.drop_semantic_model(
+    NameIdentifier.of("mart", "imported_sales_model"))
+```
+
+</TabItem>
+</Tabs>
+
+REST returns `{"code":0,"dropped":true}` when the model is dropped, while the 
SDKs return a boolean.
+An authorized request for an absent model returns `false` (`dropped: false` in 
REST).
+
+## Other Interfaces
+
+The [Gravitino MCP server](./gravitino-mcp-server.md#semantic-models) provides
+`list_of_semantic_models`, `load_semantic_model`, `create_semantic_model`, 
`alter_semantic_model`,
+and `drop_semantic_model`. Enable the `semantic_model` tool tag when filtering 
tools.
+Create and alter use the native REST definition format. Use REST or the SDKs 
for Ossie import and
+export. The current Web UI does not provide Semantic Model workflows.
+
+## Troubleshooting
+
+| HTTP status | What to check |
+|-------------|---------------|
+| `400` | Definition or document syntax, source identifiers, missing sources, 
key or relationship columns, and supported export formats. |

Review Comment:
   Removed the troubleshooting table to avoid duplicating the OpenAPI error 
responses. The create section already states that `from` and `to` name datasets 
in the model.



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