feat(dataset-groups): CRUD, latest-in-group, group SLD with dataset fallback, CreateRasterFromFile

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
2026-09-05 13:29:01 +05:00
parent 32eba016b3
commit bc524f3d98
11 changed files with 1366 additions and 34 deletions
--- a/README.md
+++ b/README.md
@@ -32,6 +32,9 @@ api/openapi.yaml         OpenAPI 3.1.1 spec (embedded + served at /openapi.yaml)

 - **Category** — hierarchical (self-referencing `parent_id`). Full CRUD; cycle-safe
  on update.
+- **DatasetGroup** — a named group of "одноимённые" datasets (see *Dataset
+  groups* below). Full CRUD; deleting a group still referenced by datasets is
+  rejected with 409.
 - **Dataset** — a geo file uploaded to S3/MinIO (`file_type`: `vector_with_kato |
  vector | raster`), belonging to one Category. Carries `code`/`name`/`description`/
  `unit` metadata, a user-defined `meta` (JSONB) blob, an `automated` flag, a
@@ -103,6 +106,26 @@ three are accepted on `POST /datasets` (form fields), `PUT /datasets/{id}` and
 `?start_date_from=`, `?start_date_to=`, `?end_date_from=` and `?end_date_to=`
 (each `YYYY-MM-DD`).

+### Dataset groups
+
+A **dataset group** (`/dataset-groups`) collects the datasets that describe the
+same indicator for different periods — the "одноимённые" datasets. A group has a
+slug `code` (unique), a `name` and a `description`, and datasets join it through
+their `dg_id`.
+
+**Freshness.** `GET /dataset-groups/{id}/latest` returns the group's freshest
+dataset: the greatest `end_date` wins, datasets without an `end_date` come last,
+and ties are broken by the newest `created_at`. Narrow the candidates with
+`?status=` and `?file_type=` (for example `?status=ready&file_type=raster` to
+get the latest published raster). A group with no matching dataset yields 404.
+
+**Shared SLD.** A group can carry one SLD (Styled Layer Descriptor) style file
+(`POST`/`GET /dataset-groups/{id}/sld`, multipart `file`, `.sld` or `.xml`),
+which acts as the fallback style for every dataset in the group:
+`GET /datasets/{id}/sld` returns the dataset's own SLD when it has one, and
+otherwise falls back to its group's — 404 only when neither exists. Deleting a
+group also removes its stored SLD object.
+
 ## Getting started

 ```sh
@@ -138,7 +161,17 @@ server runs it is served at `/openapi.yaml`, with an interactive **Redoc** UI at
 | GET    | `/datasets/{id}/download`  | download the stored file             |
 | POST   | `/datasets/{id}/mapping`   | set KATO column + year→period map (vector_with_kato) |
 | GET    | `/datasets/{id}/observations` | paginated unpivoted values (`?kato_code=`, `?page=`, `?page_size=`) |
+| POST   | `/datasets/{id}/sld`       | upload/replace the dataset's SLD (multipart `file`, `.sld`/`.xml`) |
+| GET    | `/datasets/{id}/sld`       | download the dataset's SLD, falling back to its group's |
 | DELETE | `/datasets/{id}`           | delete (row + object)                |
+| GET    | `/dataset-groups`          | paginated list (`?code=`, `?page=`, `?page_size=`) |
+| POST   | `/dataset-groups`          | create (`code`, `name`, `description?`) |
+| GET    | `/dataset-groups/{id}`     | get                                  |
+| PUT    | `/dataset-groups/{id}`     | update                               |
+| DELETE | `/dataset-groups/{id}`     | delete (409 while datasets reference it) |
+| GET    | `/dataset-groups/{id}/latest` | freshest dataset of the group (`?status=`, `?file_type=`) |
+| POST   | `/dataset-groups/{id}/sld` | upload/replace the group's shared SLD |
+| GET    | `/dataset-groups/{id}/sld` | download the group's shared SLD      |

 Example upload:

--- a/api/openapi.yaml
+++ b/api/openapi.yaml
@@ -33,6 +33,8 @@ tags:
    description: Hierarchical dataset categories
  - name: Datasets
    description: Geo dataset upload, processing, and retrieval
+  - name: Dataset Groups
+    description: Groups of same-named datasets versioned by period

 paths:
  /healthz:
@@ -151,6 +153,165 @@ paths:
        "404": { $ref: "#/components/responses/NotFound" }
        "409": { $ref: "#/components/responses/Conflict" }

+  /dataset-groups:
+    get:
+      tags: [Dataset Groups]
+      summary: List dataset groups (paginated)
+      parameters:
+        - name: code
+          in: query
+          required: false
+          description: Filter by exact group code.
+          schema:
+            type: string
+        - $ref: "#/components/parameters/PageParam"
+        - $ref: "#/components/parameters/PageSizeParam"
+      responses:
+        "200":
+          description: Groups ordered by code
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/DatasetGroupPage" }
+        "400": { $ref: "#/components/responses/BadRequest" }
+    post:
+      tags: [Dataset Groups]
+      summary: Create a dataset group
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema: { $ref: "#/components/schemas/DatasetGroupInput" }
+      responses:
+        "201":
+          description: Created
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/DatasetGroup" }
+        "400": { $ref: "#/components/responses/BadRequest" }
+        "409": { $ref: "#/components/responses/Conflict" }
+        "422": { $ref: "#/components/responses/ValidationError" }
+
+  /dataset-groups/{id}:
+    parameters:
+      - $ref: "#/components/parameters/IdParam"
+    get:
+      tags: [Dataset Groups]
+      summary: Get a dataset group
+      responses:
+        "200":
+          description: The group
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/DatasetGroup" }
+        "400": { $ref: "#/components/responses/BadRequest" }
+        "404": { $ref: "#/components/responses/NotFound" }
+    put:
+      tags: [Dataset Groups]
+      summary: Update a dataset group
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema: { $ref: "#/components/schemas/DatasetGroupInput" }
+      responses:
+        "200":
+          description: Updated
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/DatasetGroup" }
+        "400": { $ref: "#/components/responses/BadRequest" }
+        "404": { $ref: "#/components/responses/NotFound" }
+        "409": { $ref: "#/components/responses/Conflict" }
+        "422": { $ref: "#/components/responses/ValidationError" }
+    delete:
+      tags: [Dataset Groups]
+      summary: Delete a dataset group
+      description: Fails with 409 if datasets still reference the group.
+      responses:
+        "204": { description: Deleted }
+        "400": { $ref: "#/components/responses/BadRequest" }
+        "404": { $ref: "#/components/responses/NotFound" }
+        "409": { $ref: "#/components/responses/Conflict" }
+
+  /dataset-groups/{id}/latest:
+    parameters:
+      - $ref: "#/components/parameters/IdParam"
+    get:
+      tags: [Dataset Groups]
+      summary: Get the freshest dataset of a group
+      description: |
+        Returns the group's dataset with the greatest `end_date` (datasets
+        without an `end_date` come last, ties broken by newest `created_at`).
+        Returns 404 when the group does not exist or has no matching dataset.
+      parameters:
+        - name: status
+          in: query
+          required: false
+          description: Only consider datasets in this status.
+          schema: { $ref: "#/components/schemas/DatasetStatus" }
+        - name: file_type
+          in: query
+          required: false
+          description: Only consider datasets of this file type.
+          schema: { $ref: "#/components/schemas/FileType" }
+      responses:
+        "200":
+          description: The freshest dataset in the group
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/Dataset" }
+        "400": { $ref: "#/components/responses/BadRequest" }
+        "404": { $ref: "#/components/responses/NotFound" }
+
+  /dataset-groups/{id}/sld:
+    parameters:
+      - $ref: "#/components/parameters/IdParam"
+    post:
+      tags: [Dataset Groups]
+      summary: Upload (or replace) a group's shared SLD style file
+      description: |
+        Multipart upload of an SLD (Styled Layer Descriptor) style file shared by
+        every dataset of the group. A dataset with no SLD of its own falls back
+        to this one on `GET /datasets/{id}/sld`. Uploading again replaces the
+        previously stored SLD.
+
+        Allowed extensions: `.sld`, `.xml`.
+      requestBody:
+        required: true
+        content:
+          multipart/form-data:
+            schema:
+              type: object
+              required: [file]
+              properties:
+                file:
+                  type: string
+                  format: binary
+                  description: The SLD file.
+      responses:
+        "200":
+          description: SLD stored; the updated group
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/DatasetGroup" }
+        "400": { $ref: "#/components/responses/BadRequest" }
+        "404": { $ref: "#/components/responses/NotFound" }
+        "422": { $ref: "#/components/responses/ValidationError" }
+    get:
+      tags: [Dataset Groups]
+      summary: Download a group's shared SLD style file
+      description: Returns 404 if no SLD has been uploaded for this group yet.
+      responses:
+        "200":
+          description: The SLD file stream
+          content:
+            application/xml:
+              schema:
+                type: string
+                format: binary
+        "400": { $ref: "#/components/responses/BadRequest" }
+        "404": { $ref: "#/components/responses/NotFound" }
+
  /datasets:
    get:
      tags: [Datasets]
@@ -518,7 +679,10 @@ paths:
    get:
      tags: [Datasets]
      summary: Download a dataset's SLD style file
-      description: Returns 404 if no SLD has been uploaded for this dataset yet.
+      description: |
+        Returns the dataset's own SLD. When the dataset has none but belongs to a
+        dataset group that carries a shared SLD, the group's SLD is returned
+        instead. Returns 404 when neither exists.
      responses:
        "200":
          description: The SLD file stream
@@ -676,6 +840,70 @@ components:
      description: Dataset processing lifecycle status.
      enum: [pending, processing, parsing, awaiting_mapping, extracting, ready, failed]

+    DatasetGroup:
+      type: object
+      description: |
+        A group of same-named datasets delivered for different periods. The
+        freshest member is the one with the greatest `end_date`.
+      required: [id, code, name, description, created_at, updated_at]
+      properties:
+        id:
+          type: string
+          format: uuid
+        code:
+          type: string
+          description: Slug (lowercase latin letters, digits, and dashes).
+        name:
+          type: string
+        description:
+          type: string
+        sld_storage_key:
+          type: [string, "null"]
+          description: Object-store key of the group's shared SLD, if uploaded.
+        sld_filename:
+          type: [string, "null"]
+        sld_content_type:
+          type: [string, "null"]
+        created_at:
+          type: string
+          format: date-time
+        updated_at:
+          type: string
+          format: date-time
+
+    DatasetGroupInput:
+      type: object
+      required: [code, name]
+      properties:
+        code:
+          type: string
+          maxLength: 255
+          pattern: "^[a-z0-9]+(?:-[a-z0-9]+)*$"
+          description: Slug (lowercase latin letters, digits, and dashes).
+        name:
+          type: string
+          maxLength: 255
+        description:
+          type: string
+          maxLength: 2000
+
+    DatasetGroupPage:
+      type: object
+      required: [data, page, page_size, total, total_pages]
+      properties:
+        data:
+          type: array
+          items:
+            $ref: "#/components/schemas/DatasetGroup"
+        page:
+          type: integer
+        page_size:
+          type: integer
+        total:
+          type: integer
+        total_pages:
+          type: integer
+
    Category:
      type: object
      required: [id, code, name, description, created_at, updated_at]
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -38,6 +38,7 @@ type App struct {
 	publisher  *rabbitmq.Publisher
 	categories *service.CategoryService
 	datasets   *service.DatasetService
+	groups     *service.DatasetGroupService
 	eventRepo  *postgres.EventRepository
 }

@@ -68,6 +69,7 @@ func New(ctx context.Context) (*App, error) {

 	categoryRepo := postgres.NewCategoryRepository(pool)
 	datasetRepo := postgres.NewDatasetRepository(pool)
+	groupRepo := postgres.NewDatasetGroupRepository(pool)
 	eventRepo := postgres.NewEventRepository(pool)

 	publisher := rabbitmq.NewPublisher(rabbit)
@@ -81,7 +83,8 @@ func New(ctx context.Context) (*App, error) {
 		rabbit:     rabbit,
 		publisher:  publisher,
 		categories: service.NewCategoryService(categoryRepo),
-		datasets:   service.NewDatasetService(datasetRepo, store, categoryRepo, jobPublisher, parser.Columns, parser.Rows, raster.NewGDALConverter()),
+		datasets:   service.NewDatasetService(datasetRepo, store, categoryRepo, groupRepo, jobPublisher, parser.Columns, parser.Rows, raster.NewGDALConverter()),
+		groups:     service.NewDatasetGroupService(groupRepo, datasetRepo, store),
 		eventRepo:  eventRepo,
 	}, nil
 }
@@ -104,6 +107,7 @@ func (a *App) Handler() stdhttp.Handler {
 		Health:        health,
 		Categories:    transporthttp.NewCategoryHandler(a.categories, validate),
 		Datasets:      transporthttp.NewDatasetHandler(a.datasets, validate),
+		DatasetGroups: transporthttp.NewDatasetGroupHandler(a.groups, validate),
 		OpenAPISpec:   api.Spec,
 	})
 }
--- a/internal/domain/dataset_group.go
+++ b/internal/domain/dataset_group.go
@@ -0,0 +1,23 @@
+package domain
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// DatasetGroup groups "одноимённые" datasets (the same indicator delivered for
+// different periods). The freshest dataset of a group is the one with the
+// greatest end_date. A group may carry a shared SLD style used as a fallback by
+// datasets that have none of their own.
+type DatasetGroup struct {
+	ID             uuid.UUID `json:"id"`
+	Code           string    `json:"code"`
+	Name           string    `json:"name"`
+	Description    string    `json:"description"`
+	SldStorageKey  *string   `json:"sld_storage_key"`
+	SldFilename    *string   `json:"sld_filename"`
+	SldContentType *string   `json:"sld_content_type"`
+	CreatedAt      time.Time `json:"created_at"`
+	UpdatedAt      time.Time `json:"updated_at"`
+}
--- a/internal/repository/postgres/dataset_group.go
+++ b/internal/repository/postgres/dataset_group.go
@@ -0,0 +1,117 @@
+package postgres
+
+import (
+	"context"
+	"fmt"
+
+	"gis/internal/domain"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// DatasetGroupRepository persists dataset groups in Postgres.
+type DatasetGroupRepository struct{ pool *pgxpool.Pool }
+
+// NewDatasetGroupRepository returns a DatasetGroupRepository backed by pool.
+func NewDatasetGroupRepository(pool *pgxpool.Pool) *DatasetGroupRepository {
+	return &DatasetGroupRepository{pool: pool}
+}
+
+const datasetGroupColumns = `id, code, name, description, sld_storage_key, sld_filename, sld_content_type, created_at, updated_at`
+
+func scanDatasetGroup(row pgx.Row) (domain.DatasetGroup, error) {
+	var g domain.DatasetGroup
+	err := row.Scan(&g.ID, &g.Code, &g.Name, &g.Description, &g.SldStorageKey, &g.SldFilename, &g.SldContentType, &g.CreatedAt, &g.UpdatedAt)
+	return g, err
+}
+
+// Create inserts a new dataset group and returns the stored row.
+func (r *DatasetGroupRepository) Create(ctx context.Context, g domain.DatasetGroup) (domain.DatasetGroup, error) {
+	row := r.pool.QueryRow(ctx,
+		`INSERT INTO dataset_groups (code, name, description) VALUES ($1, $2, $3) RETURNING `+datasetGroupColumns,
+		g.Code, g.Name, g.Description)
+	out, err := scanDatasetGroup(row)
+	return out, mapError(err)
+}
+
+// GetByID returns the group with the given id.
+func (r *DatasetGroupRepository) GetByID(ctx context.Context, id uuid.UUID) (domain.DatasetGroup, error) {
+	out, err := scanDatasetGroup(r.pool.QueryRow(ctx, `SELECT `+datasetGroupColumns+` FROM dataset_groups WHERE id = $1`, id))
+	return out, mapError(err)
+}
+
+// GetByCode returns the group with the given (unique) code.
+func (r *DatasetGroupRepository) GetByCode(ctx context.Context, code string) (domain.DatasetGroup, error) {
+	out, err := scanDatasetGroup(r.pool.QueryRow(ctx, `SELECT `+datasetGroupColumns+` FROM dataset_groups WHERE code = $1`, code))
+	return out, mapError(err)
+}
+
+// List returns a page of groups ordered by code; code (exact) is optional.
+func (r *DatasetGroupRepository) List(ctx context.Context, code *string, limit, offset int) ([]domain.DatasetGroup, error) {
+	where, args := groupWhere(code)
+	args = append(args, limit, offset)
+	rows, err := r.pool.Query(ctx, fmt.Sprintf(`SELECT %s FROM dataset_groups%s ORDER BY code LIMIT $%d OFFSET $%d`,
+		datasetGroupColumns, where, len(args)-1, len(args)), args...)
+	if err != nil {
+		return nil, mapError(err)
+	}
+	defer rows.Close()
+	out := make([]domain.DatasetGroup, 0)
+	for rows.Next() {
+		g, err := scanDatasetGroup(rows)
+		if err != nil {
+			return nil, mapError(err)
+		}
+		out = append(out, g)
+	}
+	return out, mapError(rows.Err())
+}
+
+// Count returns how many groups match the optional code filter.
+func (r *DatasetGroupRepository) Count(ctx context.Context, code *string) (int, error) {
+	where, args := groupWhere(code)
+	var n int
+	err := r.pool.QueryRow(ctx, `SELECT count(*) FROM dataset_groups`+where, args...).Scan(&n)
+	return n, mapError(err)
+}
+
+// groupWhere builds the optional exact-code WHERE clause and its arguments.
+func groupWhere(code *string) (string, []any) {
+	if code == nil {
+		return "", nil
+	}
+	return " WHERE code = $1", []any{*code}
+}
+
+// Update replaces a group's editable fields and returns the stored row.
+func (r *DatasetGroupRepository) Update(ctx context.Context, g domain.DatasetGroup) (domain.DatasetGroup, error) {
+	row := r.pool.QueryRow(ctx,
+		`UPDATE dataset_groups SET code = $2, name = $3, description = $4, updated_at = now() WHERE id = $1 RETURNING `+datasetGroupColumns,
+		g.ID, g.Code, g.Name, g.Description)
+	out, err := scanDatasetGroup(row)
+	return out, mapError(err)
+}
+
+// Delete removes a group. Returns domain.ErrNotFound if absent and
+// domain.ErrConflict (via the FK) if datasets still reference it.
+func (r *DatasetGroupRepository) Delete(ctx context.Context, id uuid.UUID) error {
+	tag, err := r.pool.Exec(ctx, `DELETE FROM dataset_groups WHERE id = $1`, id)
+	if err != nil {
+		return mapError(err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+// SetSLD points the group at a stored SLD style object.
+func (r *DatasetGroupRepository) SetSLD(ctx context.Context, id uuid.UUID, key, filename, contentType string) (domain.DatasetGroup, error) {
+	row := r.pool.QueryRow(ctx,
+		`UPDATE dataset_groups SET sld_storage_key = $2, sld_filename = $3, sld_content_type = $4, updated_at = now() WHERE id = $1 RETURNING `+datasetGroupColumns,
+		id, key, filename, contentType)
+	out, err := scanDatasetGroup(row)
+	return out, mapError(err)
+}
--- a/internal/service/dataset.go
+++ b/internal/service/dataset.go
@@ -86,6 +86,12 @@ type categoryReader interface {
 	GetByCode(ctx context.Context, code string) (domain.Category, error)
 }

+// groupReader lets the dataset service verify a dataset group exists before a
+// dataset is filed under it, and resolve its shared SLD as a fallback.
+type groupReader interface {
+	GetByID(ctx context.Context, id uuid.UUID) (domain.DatasetGroup, error)
+}
+
 // JobEnqueuer schedules asynchronous dataset jobs.
 type JobEnqueuer interface {
 	EnqueueParse(ctx context.Context, datasetID uuid.UUID) error
@@ -138,6 +144,7 @@ type DatasetService struct {
 	repo         DatasetRepository
 	store        ObjectStore
 	categories   categoryReader
+	groups       groupReader
 	jobs         JobEnqueuer
 	parseColumns ColumnParser
 	parseRows    RowParser
@@ -145,12 +152,14 @@ type DatasetService struct {
 }

 // NewDatasetService wires the dataset repository, object store, category reader
-// (for parent validation), the job enqueuer, the column/row parsers, and the
-// raster converter.
+// (for parent validation), the dataset-group reader (for group validation and
+// the SLD fallback), the job enqueuer, the column/row parsers, and the raster
+// converter.
 func NewDatasetService(
 	repo DatasetRepository,
 	store ObjectStore,
 	categories categoryReader,
+	groups groupReader,
 	jobs JobEnqueuer,
 	parseColumns ColumnParser,
 	parseRows RowParser,
@@ -160,6 +169,7 @@ func NewDatasetService(
 		repo:         repo,
 		store:        store,
 		categories:   categories,
+		groups:       groups,
 		jobs:         jobs,
 		parseColumns: parseColumns,
 		parseRows:    parseRows,
@@ -196,6 +206,9 @@ func (s *DatasetService) Upload(ctx context.Context, in UploadInput) (domain.Dat
 	if err := s.ensureCategoryExists(ctx, in.CategoryID); err != nil {
 		return domain.Dataset{}, err
 	}
+	if err := s.ensureGroupExists(ctx, in.DatasetGroupID); err != nil {
+		return domain.Dataset{}, err
+	}
 	if err := domain.ValidateDatePeriod(in.StartDate, in.EndDate); err != nil {
 		return domain.Dataset{}, err
 	}
@@ -311,8 +324,24 @@ func (s *DatasetService) DownloadSLD(ctx context.Context, id uuid.UUID) (domain.
 		return domain.Dataset{}, nil, err
 	}
 	if dataset.SldStorageKey == nil {
+		// Fall back to the dataset group's shared style, if the group has one.
+		if dataset.DatasetGroupID == nil {
 			return domain.Dataset{}, nil, ErrSLDNotFound
 		}
+		group, err := s.groups.GetByID(ctx, *dataset.DatasetGroupID)
+		if err != nil {
+			if errors.Is(err, domain.ErrNotFound) {
+				return domain.Dataset{}, nil, ErrSLDNotFound
+			}
+			return domain.Dataset{}, nil, err
+		}
+		if group.SldStorageKey == nil {
+			return domain.Dataset{}, nil, ErrSLDNotFound
+		}
+		dataset.SldStorageKey = group.SldStorageKey
+		dataset.SldFilename = group.SldFilename
+		dataset.SldContentType = group.SldContentType
+	}
 	obj, err := s.store.Get(ctx, *dataset.SldStorageKey)
 	if err != nil {
 		return domain.Dataset{}, nil, err
@@ -320,6 +349,48 @@ func (s *DatasetService) DownloadSLD(ctx context.Context, id uuid.UUID) (domain.
 	return dataset, obj, nil
 }

+// CreateRasterInput describes a raster file already on local disk that should
+// become a dataset (used by the Landscape Program to publish results).
+type CreateRasterInput struct {
+	CategoryID     uuid.UUID
+	DatasetGroupID *uuid.UUID
+	Name           string
+	Filename       string // stored filename, e.g. "lp-z-integrated.tif"
+	Path           string // local path to read from
+	StartDate      *string
+	EndDate        *string
+	Meta           json.RawMessage
+	Automated      bool
+}
+
+// CreateRasterFromFile stores a local GeoTIFF as a new raster dataset and
+// enqueues the standard COG conversion, exactly like an uploaded raster.
+func (s *DatasetService) CreateRasterFromFile(ctx context.Context, in CreateRasterInput) (domain.Dataset, error) {
+	f, err := os.Open(in.Path)
+	if err != nil {
+		return domain.Dataset{}, err
+	}
+	defer f.Close()
+	info, err := f.Stat()
+	if err != nil {
+		return domain.Dataset{}, err
+	}
+	return s.Upload(ctx, UploadInput{
+		CategoryID:     in.CategoryID,
+		DatasetGroupID: in.DatasetGroupID,
+		Name:           in.Name,
+		Meta:           in.Meta,
+		Automated:      in.Automated,
+		Filename:       in.Filename,
+		FileType:       domain.FileTypeRaster,
+		ContentType:    "image/tiff",
+		Size:           info.Size(),
+		Reader:         f,
+		StartDate:      in.StartDate,
+		EndDate:        in.EndDate,
+	})
+}
+
 // deriveSLDKey places a dataset's SLD style file alongside the original under
 // an sld/ prefix, named after the uploaded SLD file.
 func deriveSLDKey(storageKey, filename string) string {
@@ -1099,6 +1170,9 @@ func (s *DatasetService) Update(ctx context.Context, id uuid.UUID, in DatasetUpd
 	if err := s.ensureCategoryExists(ctx, in.CategoryID); err != nil {
 		return domain.Dataset{}, err
 	}
+	if err := s.ensureGroupExists(ctx, in.DatasetGroupID); err != nil {
+		return domain.Dataset{}, err
+	}
 	if err := domain.ValidateDatePeriod(in.StartDate, in.EndDate); err != nil {
 		return domain.Dataset{}, err
 	}
@@ -1163,6 +1237,9 @@ func (s *DatasetService) Patch(ctx context.Context, id uuid.UUID, in DatasetPatc
 	groupID := current.DatasetGroupID
 	if in.DatasetGroupIDSet {
 		groupID = in.DatasetGroupID
+		if err := s.ensureGroupExists(ctx, groupID); err != nil {
+			return domain.Dataset{}, err
+		}
 	}
 	startDate := current.StartDate
 	if in.StartDateSet {
@@ -1199,6 +1276,21 @@ func (s *DatasetService) ensureCategoryExists(ctx context.Context, categoryID uu
 	return nil
 }

+// ensureGroupExists validates that a non-nil dataset group id references an
+// existing group. A nil id (no group) is always valid.
+func (s *DatasetService) ensureGroupExists(ctx context.Context, id *uuid.UUID) error {
+	if id == nil {
+		return nil
+	}
+	if _, err := s.groups.GetByID(ctx, *id); err != nil {
+		if errors.Is(err, domain.ErrNotFound) {
+			return fmt.Errorf("%w: dataset group %s not found", domain.ErrValidation, id)
+		}
+		return err
+	}
+	return nil
+}
+
 // Status-wait bounds and polling cadence for long polling.
 const (
 	DefaultStatusWait  = 25 * time.Second
--- a/internal/service/dataset_group.go
+++ b/internal/service/dataset_group.go
@@ -0,0 +1,185 @@
+package service
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"gis/internal/domain"
+
+	"github.com/google/uuid"
+)
+
+// DatasetGroupRepository is the persistence behaviour DatasetGroupService needs.
+type DatasetGroupRepository interface {
+	Create(ctx context.Context, g domain.DatasetGroup) (domain.DatasetGroup, error)
+	GetByID(ctx context.Context, id uuid.UUID) (domain.DatasetGroup, error)
+	GetByCode(ctx context.Context, code string) (domain.DatasetGroup, error)
+	List(ctx context.Context, code *string, limit, offset int) ([]domain.DatasetGroup, error)
+	Count(ctx context.Context, code *string) (int, error)
+	Update(ctx context.Context, g domain.DatasetGroup) (domain.DatasetGroup, error)
+	Delete(ctx context.Context, id uuid.UUID) error
+	SetSLD(ctx context.Context, id uuid.UUID, key, filename, contentType string) (domain.DatasetGroup, error)
+}
+
+// DatasetGroupInput carries the mutable fields of a group.
+type DatasetGroupInput struct {
+	Code        string
+	Name        string
+	Description string
+}
+
+// DatasetGroupPage is a page of groups.
+type DatasetGroupPage struct {
+	Items    []domain.DatasetGroup
+	Page     int
+	PageSize int
+	Total    int
+}
+
+// DatasetGroupService implements dataset-group business rules.
+type DatasetGroupService struct {
+	repo     DatasetGroupRepository
+	datasets DatasetRepository
+	store    ObjectStore
+}
+
+// NewDatasetGroupService wires the group repository, the dataset repository
+// (for the "latest" lookup) and the object store (for the group SLD).
+func NewDatasetGroupService(repo DatasetGroupRepository, datasets DatasetRepository, store ObjectStore) *DatasetGroupService {
+	return &DatasetGroupService{repo: repo, datasets: datasets, store: store}
+}
+
+// errInvalidGroupCode is the validation error returned for a non-slug code.
+func errInvalidGroupCode() error {
+	return fmt.Errorf("%w: code must be a slug (lowercase latin letters, digits, and dashes)", domain.ErrValidation)
+}
+
+// Create persists a new group after validating its code.
+func (s *DatasetGroupService) Create(ctx context.Context, in DatasetGroupInput) (domain.DatasetGroup, error) {
+	if !domain.ValidSlug(in.Code) {
+		return domain.DatasetGroup{}, errInvalidGroupCode()
+	}
+	return s.repo.Create(ctx, domain.DatasetGroup{Code: in.Code, Name: in.Name, Description: in.Description})
+}
+
+// Get returns one group by id.
+func (s *DatasetGroupService) Get(ctx context.Context, id uuid.UUID) (domain.DatasetGroup, error) {
+	return s.repo.GetByID(ctx, id)
+}
+
+// List returns a page of groups; page/pageSize are clamped like datasets.
+func (s *DatasetGroupService) List(ctx context.Context, code *string, page, pageSize int) (DatasetGroupPage, error) {
+	if page < 1 {
+		page = 1
+	}
+	if pageSize < 1 {
+		pageSize = DefaultPageSize
+	}
+	if pageSize > MaxPageSize {
+		pageSize = MaxPageSize
+	}
+	items, err := s.repo.List(ctx, code, pageSize, (page-1)*pageSize)
+	if err != nil {
+		return DatasetGroupPage{}, err
+	}
+	total, err := s.repo.Count(ctx, code)
+	if err != nil {
+		return DatasetGroupPage{}, err
+	}
+	return DatasetGroupPage{Items: items, Page: page, PageSize: pageSize, Total: total}, nil
+}
+
+// Update replaces a group's editable fields.
+func (s *DatasetGroupService) Update(ctx context.Context, id uuid.UUID, in DatasetGroupInput) (domain.DatasetGroup, error) {
+	if !domain.ValidSlug(in.Code) {
+		return domain.DatasetGroup{}, errInvalidGroupCode()
+	}
+	return s.repo.Update(ctx, domain.DatasetGroup{ID: id, Code: in.Code, Name: in.Name, Description: in.Description})
+}
+
+// Delete removes a group (409 via ErrConflict while datasets reference it) and
+// then best-effort removes its SLD object.
+func (s *DatasetGroupService) Delete(ctx context.Context, id uuid.UUID) error {
+	g, err := s.repo.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+	if err := s.repo.Delete(ctx, id); err != nil {
+		return err
+	}
+	if g.SldStorageKey != nil {
+		_ = s.store.Remove(ctx, *g.SldStorageKey) // best-effort: the row is gone
+	}
+	return nil
+}
+
+// Latest returns the freshest dataset of the group (greatest end_date, NULLs
+// last, then newest), optionally restricted by status and file type.
+func (s *DatasetGroupService) Latest(ctx context.Context, id uuid.UUID, status *string, fileType *domain.FileType) (domain.Dataset, error) {
+	if _, err := s.repo.GetByID(ctx, id); err != nil {
+		return domain.Dataset{}, err
+	}
+	return s.datasets.LatestInGroup(ctx, id, status, fileType)
+}
+
+// UploadSLD validates and stores the group's shared SLD, replacing any previous one.
+func (s *DatasetGroupService) UploadSLD(ctx context.Context, id uuid.UUID, in UploadSLDInput) (domain.DatasetGroup, error) {
+	g, err := s.repo.GetByID(ctx, id)
+	if err != nil {
+		return domain.DatasetGroup{}, err
+	}
+
+	ext := strings.ToLower(filepath.Ext(in.Filename))
+	if !domain.ExtensionAllowedForSLD(ext) {
+		return domain.DatasetGroup{}, fmt.Errorf("%w: sld file must have one of these extensions: %s",
+			domain.ErrValidation, strings.Join(domain.AllowedSLDExtensions, ", "))
+	}
+
+	head := make([]byte, 512)
+	n, err := io.ReadFull(in.Reader, head)
+	if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
+		return domain.DatasetGroup{}, fmt.Errorf("read sld upload: %w", err)
+	}
+	head = head[:n]
+	if err := domain.ValidateFileContent(ext, head); err != nil {
+		return domain.DatasetGroup{}, fmt.Errorf("%w: %s", domain.ErrValidation, err)
+	}
+	content := io.MultiReader(bytes.NewReader(head), in.Reader)
+
+	key := path.Join("groups", g.ID.String(), "sld", in.Filename)
+	if err := s.store.Put(ctx, key, content, in.Size, in.ContentType); err != nil {
+		return domain.DatasetGroup{}, err
+	}
+	updated, err := s.repo.SetSLD(ctx, id, key, in.Filename, in.ContentType)
+	if err != nil {
+		// Compensate: the row was not updated, so the object would be orphaned.
+		_ = s.store.Remove(ctx, key)
+		return domain.DatasetGroup{}, err
+	}
+	if g.SldStorageKey != nil && *g.SldStorageKey != key {
+		_ = s.store.Remove(ctx, *g.SldStorageKey) // best-effort: drop the replaced file
+	}
+	return updated, nil
+}
+
+// DownloadSLD returns the group and a reader for its SLD; ErrSLDNotFound when
+// none has been uploaded. The caller must close the reader.
+func (s *DatasetGroupService) DownloadSLD(ctx context.Context, id uuid.UUID) (domain.DatasetGroup, io.ReadCloser, error) {
+	g, err := s.repo.GetByID(ctx, id)
+	if err != nil {
+		return domain.DatasetGroup{}, nil, err
+	}
+	if g.SldStorageKey == nil {
+		return domain.DatasetGroup{}, nil, ErrSLDNotFound
+	}
+	obj, err := s.store.Get(ctx, *g.SldStorageKey)
+	if err != nil {
+		return domain.DatasetGroup{}, nil, err
+	}
+	return g, obj, nil
+}
--- a/internal/service/dataset_group_test.go
+++ b/internal/service/dataset_group_test.go
@@ -0,0 +1,257 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+	"time"
+
+	"gis/internal/domain"
+
+	"github.com/google/uuid"
+)
+
+// stubGroupRepo is an in-memory DatasetGroupRepository for tests. It also
+// satisfies the dataset service's groupReader dependency.
+type stubGroupRepo struct {
+	store map[uuid.UUID]domain.DatasetGroup
+}
+
+func newStubGroupRepo() *stubGroupRepo {
+	return &stubGroupRepo{store: map[uuid.UUID]domain.DatasetGroup{}}
+}
+
+func (r *stubGroupRepo) Create(_ context.Context, g domain.DatasetGroup) (domain.DatasetGroup, error) {
+	for _, e := range r.store {
+		if e.Code == g.Code {
+			return domain.DatasetGroup{}, domain.ErrConflict
+		}
+	}
+	g.ID = uuid.New()
+	r.store[g.ID] = g
+	return g, nil
+}
+
+func (r *stubGroupRepo) GetByID(_ context.Context, id uuid.UUID) (domain.DatasetGroup, error) {
+	g, ok := r.store[id]
+	if !ok {
+		return domain.DatasetGroup{}, domain.ErrNotFound
+	}
+	return g, nil
+}
+
+func (r *stubGroupRepo) GetByCode(_ context.Context, code string) (domain.DatasetGroup, error) {
+	for _, g := range r.store {
+		if g.Code == code {
+			return g, nil
+		}
+	}
+	return domain.DatasetGroup{}, domain.ErrNotFound
+}
+
+func (r *stubGroupRepo) List(_ context.Context, code *string, _, _ int) ([]domain.DatasetGroup, error) {
+	out := []domain.DatasetGroup{}
+	for _, g := range r.store {
+		if code == nil || g.Code == *code {
+			out = append(out, g)
+		}
+	}
+	return out, nil
+}
+
+func (r *stubGroupRepo) Count(_ context.Context, code *string) (int, error) {
+	l, _ := r.List(context.Background(), code, 0, 0)
+	return len(l), nil
+}
+
+func (r *stubGroupRepo) Update(_ context.Context, g domain.DatasetGroup) (domain.DatasetGroup, error) {
+	if _, ok := r.store[g.ID]; !ok {
+		return domain.DatasetGroup{}, domain.ErrNotFound
+	}
+	r.store[g.ID] = g
+	return g, nil
+}
+
+func (r *stubGroupRepo) Delete(_ context.Context, id uuid.UUID) error {
+	if _, ok := r.store[id]; !ok {
+		return domain.ErrNotFound
+	}
+	delete(r.store, id)
+	return nil
+}
+
+func (r *stubGroupRepo) SetSLD(_ context.Context, id uuid.UUID, key, filename, contentType string) (domain.DatasetGroup, error) {
+	g, ok := r.store[id]
+	if !ok {
+		return domain.DatasetGroup{}, domain.ErrNotFound
+	}
+	g.SldStorageKey, g.SldFilename, g.SldContentType = &key, &filename, &contentType
+	r.store[id] = g
+	return g, nil
+}
+
+func TestDatasetGroupService_Create_RequiresSlug(t *testing.T) {
+	svc := NewDatasetGroupService(newStubGroupRepo(), newStubDatasetRepo(), newStubStore())
+	_, err := svc.Create(context.Background(), DatasetGroupInput{Code: "Bad Code", Name: "x"})
+	if !errors.Is(err, domain.ErrValidation) {
+		t.Fatalf("want ErrValidation, got %v", err)
+	}
+}
+
+func TestDatasetGroupService_Latest_PrefersGreatestEndDateThenCreatedAt(t *testing.T) {
+	groups := newStubGroupRepo()
+	datasets := newStubDatasetRepo()
+	svc := NewDatasetGroupService(groups, datasets, newStubStore())
+	g, err := svc.Create(context.Background(), DatasetGroupInput{Code: "pop", Name: "Population"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	s := func(v string) *string { return &v }
+	base := time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC)
+	old := domain.Dataset{ID: uuid.New(), DatasetGroupID: &g.ID, EndDate: s("2019-12-31"), Status: domain.DatasetStatusReady, CreatedAt: base}
+	fresh := domain.Dataset{ID: uuid.New(), DatasetGroupID: &g.ID, EndDate: s("2020-12-31"), Status: domain.DatasetStatusReady, CreatedAt: base.Add(time.Hour)}
+	undated := domain.Dataset{ID: uuid.New(), DatasetGroupID: &g.ID, Status: domain.DatasetStatusReady, CreatedAt: base.Add(2 * time.Hour)}
+	for _, d := range []domain.Dataset{old, fresh, undated} {
+		datasets.store[d.ID] = d
+	}
+	got, err := svc.Latest(context.Background(), g.ID, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.ID != fresh.ID {
+		t.Fatalf("want %s, got %s", fresh.ID, got.ID)
+	}
+}
+
+func TestDatasetGroupService_Latest_NotFoundWhenEmpty(t *testing.T) {
+	groups := newStubGroupRepo()
+	svc := NewDatasetGroupService(groups, newStubDatasetRepo(), newStubStore())
+	g, err := svc.Create(context.Background(), DatasetGroupInput{Code: "pop", Name: "Population"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := svc.Latest(context.Background(), g.ID, nil, nil); !errors.Is(err, domain.ErrNotFound) {
+		t.Fatalf("want ErrNotFound, got %v", err)
+	}
+}
+
+func TestDatasetGroupService_Latest_UnknownGroupIsNotFound(t *testing.T) {
+	svc := NewDatasetGroupService(newStubGroupRepo(), newStubDatasetRepo(), newStubStore())
+	if _, err := svc.Latest(context.Background(), uuid.New(), nil, nil); !errors.Is(err, domain.ErrNotFound) {
+		t.Fatalf("want ErrNotFound, got %v", err)
+	}
+}
+
+func TestDatasetGroupService_UploadSLD_RejectsBadExtension(t *testing.T) {
+	groups := newStubGroupRepo()
+	store := newStubStore()
+	svc := NewDatasetGroupService(groups, newStubDatasetRepo(), store)
+	g, err := svc.Create(context.Background(), DatasetGroupInput{Code: "pop", Name: "Population"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = svc.UploadSLD(context.Background(), g.ID, UploadSLDInput{Filename: "style.txt", ContentType: "text/plain", Size: 3, Reader: strings.NewReader("<x>")})
+	if !errors.Is(err, domain.ErrValidation) {
+		t.Fatalf("want ErrValidation, got %v", err)
+	}
+	if len(store.put) != 0 {
+		t.Fatalf("nothing should be stored on validation failure, got %v", store.put)
+	}
+}
+
+func TestDatasetGroupService_UploadSLD_StoresAndReplaces(t *testing.T) {
+	ctx := context.Background()
+	groups := newStubGroupRepo()
+	store := newStubStore()
+	svc := NewDatasetGroupService(groups, newStubDatasetRepo(), store)
+	g, err := svc.Create(ctx, DatasetGroupInput{Code: "pop", Name: "Population"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	updated, err := svc.UploadSLD(ctx, g.ID, UploadSLDInput{
+		Filename: "style.sld", ContentType: "application/xml", Size: 3, Reader: strings.NewReader("<x>"),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	wantKey := "groups/" + g.ID.String() + "/sld/style.sld"
+	if updated.SldStorageKey == nil || *updated.SldStorageKey != wantKey {
+		t.Fatalf("want key %s, got %v", wantKey, updated.SldStorageKey)
+	}
+
+	// A second upload under a different name replaces the previous object.
+	if _, err := svc.UploadSLD(ctx, g.ID, UploadSLDInput{
+		Filename: "other.sld", ContentType: "application/xml", Size: 3, Reader: strings.NewReader("<y>"),
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if len(store.removed) != 1 || store.removed[0] != wantKey {
+		t.Fatalf("want previous sld removed, got %v", store.removed)
+	}
+}
+
+func TestDatasetGroupService_DownloadSLD_NotFoundWhenAbsent(t *testing.T) {
+	svc := NewDatasetGroupService(newStubGroupRepo(), newStubDatasetRepo(), newStubStore())
+	g, err := svc.Create(context.Background(), DatasetGroupInput{Code: "pop", Name: "Population"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, _, err := svc.DownloadSLD(context.Background(), g.ID); !errors.Is(err, ErrSLDNotFound) {
+		t.Fatalf("want ErrSLDNotFound, got %v", err)
+	}
+}
+
+func TestDatasetGroupService_Delete_RemovesSLDObject(t *testing.T) {
+	ctx := context.Background()
+	store := newStubStore()
+	svc := NewDatasetGroupService(newStubGroupRepo(), newStubDatasetRepo(), store)
+	g, err := svc.Create(ctx, DatasetGroupInput{Code: "pop", Name: "Population"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := svc.UploadSLD(ctx, g.ID, UploadSLDInput{
+		Filename: "style.sld", ContentType: "application/xml", Size: 3, Reader: strings.NewReader("<x>"),
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := svc.Delete(ctx, g.ID); err != nil {
+		t.Fatal(err)
+	}
+	wantKey := "groups/" + g.ID.String() + "/sld/style.sld"
+	if len(store.removed) != 1 || store.removed[0] != wantKey {
+		t.Fatalf("want sld object removed, got %v", store.removed)
+	}
+	if _, err := svc.Get(ctx, g.ID); !errors.Is(err, domain.ErrNotFound) {
+		t.Fatalf("want ErrNotFound after delete, got %v", err)
+	}
+}
+
+func TestDatasetGroupService_List_ClampsPageSize(t *testing.T) {
+	svc := NewDatasetGroupService(newStubGroupRepo(), newStubDatasetRepo(), newStubStore())
+	if _, err := svc.Create(context.Background(), DatasetGroupInput{Code: "pop", Name: "Population"}); err != nil {
+		t.Fatal(err)
+	}
+	page, err := svc.List(context.Background(), nil, 0, 10_000)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if page.Page != 1 || page.PageSize != MaxPageSize {
+		t.Fatalf("want page 1 and page size %d, got %d/%d", MaxPageSize, page.Page, page.PageSize)
+	}
+	if page.Total != 1 {
+		t.Fatalf("want total 1, got %d", page.Total)
+	}
+}
+
+func TestDatasetGroupService_Update_RequiresSlug(t *testing.T) {
+	svc := NewDatasetGroupService(newStubGroupRepo(), newStubDatasetRepo(), newStubStore())
+	g, err := svc.Create(context.Background(), DatasetGroupInput{Code: "pop", Name: "Population"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := svc.Update(context.Background(), g.ID, DatasetGroupInput{Code: "Bad Code", Name: "x"}); !errors.Is(err, domain.ErrValidation) {
+		t.Fatalf("want ErrValidation, got %v", err)
+	}
+}
--- a/internal/service/dataset_test.go
+++ b/internal/service/dataset_test.go
@@ -7,6 +7,7 @@ import (
 	"errors"
 	"io"
 	"os"
+	"path/filepath"
 	"sort"
 	"strings"
 	"testing"
@@ -358,22 +359,36 @@ var (
 	noopRowParser RowParser    = func(string, []byte) ([]map[string]string, error) { return nil, nil }
 )

-// stubStore records object-store interactions.
+// stubStore records object-store interactions and keeps stored bodies so tests
+// can read them back.
 type stubStore struct {
 	put     []string
 	removed []string
 	putErr  error
+	objects map[string][]byte
 }

-func (s *stubStore) Put(_ context.Context, key string, _ io.Reader, _ int64, _ string) error {
+func newStubStore() *stubStore { return &stubStore{objects: map[string][]byte{}} }
+
+func (s *stubStore) Put(_ context.Context, key string, r io.Reader, _ int64, _ string) error {
 	if s.putErr != nil {
 		return s.putErr
 	}
 	s.put = append(s.put, key)
+	if s.objects != nil {
+		body, err := io.ReadAll(r)
+		if err != nil {
+			return err
+		}
+		s.objects[key] = body
+	}
 	return nil
 }

-func (s *stubStore) Get(_ context.Context, _ string) (io.ReadCloser, error) {
+func (s *stubStore) Get(_ context.Context, key string) (io.ReadCloser, error) {
+	if body, ok := s.objects[key]; ok {
+		return io.NopCloser(bytes.NewReader(body)), nil
+	}
 	return io.NopCloser(strings.NewReader("")), nil
 }

@@ -414,7 +429,13 @@ func validUpload() UploadInput {
 }

 func newDatasetService(repo *stubDatasetRepo, store *stubStore, catExists bool) *DatasetService {
-	return NewDatasetService(repo, store, stubCategoryReader{exists: catExists}, &stubEnqueuer{}, noopParser, noopRowParser, &stubConverter{})
+	return newDatasetServiceWithGroups(repo, store, catExists, newStubGroupRepo())
+}
+
+// newDatasetServiceWithGroups builds a DatasetService over a caller-supplied
+// group repository, for tests that need a pre-populated dataset group.
+func newDatasetServiceWithGroups(repo *stubDatasetRepo, store *stubStore, catExists bool, groups *stubGroupRepo) *DatasetService {
+	return NewDatasetService(repo, store, stubCategoryReader{exists: catExists}, groups, &stubEnqueuer{}, noopParser, noopRowParser, &stubConverter{})
 }

 func TestDatasetService_Upload_Validation(t *testing.T) {
@@ -521,7 +542,7 @@ func TestDatasetService_Upload_CompensatesOnDBFailure(t *testing.T) {
 func TestDatasetService_Upload_VectorWithKato_EnqueuesParse(t *testing.T) {
 	repo := newStubDatasetRepo()
 	enq := &stubEnqueuer{}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, enq, noopParser, noopRowParser, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), enq, noopParser, noopRowParser, &stubConverter{})

 	in := validUpload()
 	in.FileType = domain.FileTypeVectorWithKato
@@ -542,7 +563,7 @@ func TestDatasetService_Upload_VectorWithKato_EnqueuesParse(t *testing.T) {
 func TestDatasetService_Upload_Vector_EnqueuesProperties(t *testing.T) {
 	repo := newStubDatasetRepo()
 	enq := &stubEnqueuer{}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, enq, noopParser, noopRowParser, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), enq, noopParser, noopRowParser, &stubConverter{})

 	got, err := svc.Upload(context.Background(), validUpload()) // plain vector .geojson
 	if err != nil {
@@ -573,7 +594,7 @@ func TestDatasetService_ExtractProperties(t *testing.T) {
 		json.RawMessage(`{"type":"Polygon","coordinates":[[[4,4],[5,5],[6,4],[4,4]]]}`),
 	}
 	conv := &stubConverter{vectorFeatures: geoms}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, &stubEnqueuer{}, noopParser, rp, conv)
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, noopParser, rp, conv)

 	if err := svc.ExtractProperties(context.Background(), id); err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -625,7 +646,7 @@ func TestDatasetService_ExtractProperties_GeometryBestEffort(t *testing.T) {
 	conv := &stubConverter{vectorFeaturesFn: func(string) ([]json.RawMessage, error) {
 		return nil, errors.New("ogr2ogr boom")
 	}}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, &stubEnqueuer{}, noopParser, rp, conv)
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, noopParser, rp, conv)

 	if err := svc.ExtractProperties(context.Background(), id); err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -653,7 +674,7 @@ func TestDatasetService_ExtractProperties_NoTable(t *testing.T) {
 	rp := RowParser(func(string, []byte) ([]map[string]string, error) {
 		return []map[string]string{{}, {}}, nil
 	})
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, &stubEnqueuer{}, noopParser, rp, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, noopParser, rp, &stubConverter{})

 	if err := svc.ExtractProperties(context.Background(), id); err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -670,7 +691,7 @@ func TestDatasetService_ExtractProperties_NoTable(t *testing.T) {
 func TestDatasetService_Upload_Raster_EnqueuesConvert(t *testing.T) {
 	repo := newStubDatasetRepo()
 	enq := &stubEnqueuer{}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, enq, noopParser, noopRowParser, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), enq, noopParser, noopRowParser, &stubConverter{})

 	in := validUpload()
 	in.FileType = domain.FileTypeRaster
@@ -700,7 +721,7 @@ func TestDatasetService_ConvertToCOG(t *testing.T) {
 	store := &stubStore{}
 	footprint := []byte(`{"type":"Polygon","coordinates":[[[70,50],[72,50],[72,52],[70,52],[70,50]]]}`)
 	conv := &stubConverter{footprint: footprint}
-	svc := NewDatasetService(repo, store, stubCategoryReader{exists: true}, &stubEnqueuer{}, noopParser, noopRowParser, conv)
+	svc := NewDatasetService(repo, store, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, noopParser, noopRowParser, conv)

 	if err := svc.ConvertToCOG(context.Background(), id); err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -732,7 +753,7 @@ func TestDatasetService_ConvertToCOG_RecordsFailure(t *testing.T) {
 		Status: domain.DatasetStatusProcessing,
 	}
 	conv := &stubConverter{toCOGErr: errors.New("gdal failed")}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, &stubEnqueuer{}, noopParser, noopRowParser, conv)
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, noopParser, noopRowParser, conv)

 	if err := svc.ConvertToCOG(context.Background(), id); err != nil {
 		t.Fatalf("conversion failure should be recorded, not returned: %v", err)
@@ -751,7 +772,7 @@ func TestDatasetService_Parse(t *testing.T) {
 	}
 	cols := []domain.AttributeColumn{{Name: "като"}, {Name: "F_2023"}}
 	parser := ColumnParser(func(string, []byte) ([]domain.AttributeColumn, error) { return cols, nil })
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, &stubEnqueuer{}, parser, noopRowParser, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, parser, noopRowParser, &stubConverter{})

 	if err := svc.Parse(context.Background(), id); err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -775,7 +796,7 @@ func TestDatasetService_Parse_RecordsFailure(t *testing.T) {
 	parser := ColumnParser(func(string, []byte) ([]domain.AttributeColumn, error) {
 		return nil, errors.New("corrupt archive")
 	})
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, &stubEnqueuer{}, parser, noopRowParser, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, parser, noopRowParser, &stubConverter{})

 	if err := svc.Parse(context.Background(), id); err != nil {
 		t.Fatalf("parse failure should be recorded, not returned: %v", err)
@@ -886,7 +907,7 @@ func TestDatasetService_SaveMapping(t *testing.T) {
 		repo := newStubDatasetRepo()
 		repo.store[id] = base
 		enq := &stubEnqueuer{}
-		svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, enq, noopParser, noopRowParser, &stubConverter{})
+		svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), enq, noopParser, noopRowParser, &stubConverter{})

 		got, err := svc.SaveMapping(ctx, id, MappingInput{KatoColumn: "като", YearColumns: validYears})
 		if err != nil {
@@ -992,7 +1013,7 @@ func TestDatasetService_Extract(t *testing.T) {
 	geoms := []json.RawMessage{json.RawMessage(`{"type":"Polygon","coordinates":[[[76,43],[77,43],[77,44],[76,43]]]}`)}
 	geom := []byte(`{"type":"GeometryCollection","geometries":[` + string(geoms[0]) + `]}`)
 	conv := &stubConverter{vectorFeatures: geoms}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, &stubEnqueuer{}, noopParser, rp, conv)
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), &stubEnqueuer{}, noopParser, rp, conv)

 	if err := svc.Extract(context.Background(), id); err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -1427,7 +1448,7 @@ func TestDatasetService_Reprocess_ClearsStaleGeometryAndGeoJSON(t *testing.T) {
 		GeoJSON:  json.RawMessage(`{"type":"FeatureCollection","features":[{"type":"Feature","properties":{"rows":[]}}]}`),
 	}
 	enq := &stubEnqueuer{}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, enq, noopParser, noopRowParser, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), enq, noopParser, noopRowParser, &stubConverter{})

 	if _, err := svc.Reprocess(context.Background(), id); err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -1454,7 +1475,7 @@ func TestDatasetService_ReprocessAll_FiltersByFileType(t *testing.T) {
 		Geometry: json.RawMessage(`{"type":"Polygon","coordinates":[[[1,1],[2,2],[3,1],[1,1]]]}`),
 	}
 	enq := &stubEnqueuer{}
-	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, enq, noopParser, noopRowParser, &stubConverter{})
+	svc := NewDatasetService(repo, &stubStore{}, stubCategoryReader{exists: true}, newStubGroupRepo(), enq, noopParser, noopRowParser, &stubConverter{})

 	vectorType := domain.FileTypeVector
 	enqueued, failures, err := svc.ReprocessAll(context.Background(), &vectorType)
@@ -1738,9 +1759,11 @@ func TestDatasetService_Patch_NotFound(t *testing.T) {

 func TestDatasetService_Upload_StoresPeriodAndGroup(t *testing.T) {
 	repo := newStubDatasetRepo()
-	svc := newDatasetService(repo, &stubStore{}, true)
+	groups := newStubGroupRepo()
+	svc := newDatasetServiceWithGroups(repo, newStubStore(), true, groups)

 	gid := uuid.New()
+	groups.store[gid] = domain.DatasetGroup{ID: gid, Code: "pop", Name: "Population"}
 	start, end := "2020-01-01", "2020-12-31"
 	in := validUpload()
 	in.DatasetGroupID = &gid
@@ -1772,3 +1795,134 @@ func TestDatasetService_Upload_RejectsReversedPeriod(t *testing.T) {
 		t.Fatalf("nothing should be uploaded on validation failure, got %v", store.put)
 	}
 }
+
+func TestDatasetService_DownloadSLD_FallsBackToGroup(t *testing.T) {
+	ctx := context.Background()
+	repo := newStubDatasetRepo()
+	store := newStubStore()
+	groups := newStubGroupRepo()
+	svc := newDatasetServiceWithGroups(repo, store, true, groups)
+
+	groupSLD := "groups/style.sld"
+	filename, contentType := "group.sld", "application/xml"
+	group := domain.DatasetGroup{
+		ID: uuid.New(), Code: "pop", Name: "Population",
+		SldStorageKey: &groupSLD, SldFilename: &filename, SldContentType: &contentType,
+	}
+	groups.store[group.ID] = group
+	store.objects[groupSLD] = []byte("<StyledLayerDescriptor/>")
+
+	id := uuid.New()
+	repo.store[id] = domain.Dataset{ID: id, DatasetGroupID: &group.ID}
+
+	dataset, obj, err := svc.DownloadSLD(ctx, id)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer obj.Close()
+
+	if dataset.SldStorageKey == nil || *dataset.SldStorageKey != groupSLD {
+		t.Fatalf("want group sld key %s, got %v", groupSLD, dataset.SldStorageKey)
+	}
+	if dataset.SldFilename == nil || *dataset.SldFilename != filename {
+		t.Fatalf("want group sld filename %s, got %v", filename, dataset.SldFilename)
+	}
+	body, err := io.ReadAll(obj)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(body) != "<StyledLayerDescriptor/>" {
+		t.Fatalf("want the group's sld content, got %q", body)
+	}
+}
+
+func TestDatasetService_DownloadSLD_NoFallbackWhenGroupHasNoSLD(t *testing.T) {
+	repo := newStubDatasetRepo()
+	groups := newStubGroupRepo()
+	svc := newDatasetServiceWithGroups(repo, newStubStore(), true, groups)
+
+	group := domain.DatasetGroup{ID: uuid.New(), Code: "pop", Name: "Population"}
+	groups.store[group.ID] = group
+	id := uuid.New()
+	repo.store[id] = domain.Dataset{ID: id, DatasetGroupID: &group.ID}
+
+	if _, _, err := svc.DownloadSLD(context.Background(), id); !errors.Is(err, ErrSLDNotFound) {
+		t.Fatalf("want ErrSLDNotFound, got %v", err)
+	}
+}
+
+func TestDatasetService_Upload_RejectsUnknownGroup(t *testing.T) {
+	svc := newDatasetService(newStubDatasetRepo(), newStubStore(), true)
+	in := validUpload()
+	missing := uuid.New()
+	in.DatasetGroupID = &missing
+
+	if _, err := svc.Upload(context.Background(), in); !errors.Is(err, domain.ErrValidation) {
+		t.Fatalf("want ErrValidation, got %v", err)
+	}
+}
+
+func TestDatasetService_CreateRasterFromFile(t *testing.T) {
+	ctx := context.Background()
+	repo := newStubDatasetRepo()
+	store := newStubStore()
+	groups := newStubGroupRepo()
+	jobs := &stubEnqueuer{}
+	svc := NewDatasetService(repo, store, stubCategoryReader{exists: true}, groups, jobs, noopParser, noopRowParser, &stubConverter{})
+
+	group := domain.DatasetGroup{ID: uuid.New(), Code: "lp-z", Name: "Landscape Z"}
+	groups.store[group.ID] = group
+
+	// A minimal little-endian TIFF header is enough for content sniffing.
+	path := filepath.Join(t.TempDir(), "lp-z-integrated.tif")
+	if err := os.WriteFile(path, []byte("II*\x00 raster payload"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	end := "2024-12-31"
+
+	dataset, err := svc.CreateRasterFromFile(ctx, CreateRasterInput{
+		CategoryID:     uuid.New(),
+		DatasetGroupID: &group.ID,
+		Name:           "Landscape Z integrated",
+		Filename:       "lp-z-integrated.tif",
+		Path:           path,
+		EndDate:        &end,
+		Automated:      true,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if dataset.FileType != domain.FileTypeRaster {
+		t.Fatalf("want raster file type, got %q", dataset.FileType)
+	}
+	if dataset.DatasetGroupID == nil || *dataset.DatasetGroupID != group.ID {
+		t.Fatalf("want group %s, got %v", group.ID, dataset.DatasetGroupID)
+	}
+	if dataset.EndDate == nil || *dataset.EndDate != end {
+		t.Fatalf("want end date %s, got %v", end, dataset.EndDate)
+	}
+	if !dataset.Automated {
+		t.Fatal("want automated dataset")
+	}
+	if dataset.SizeBytes != int64(len("II*\x00 raster payload")) {
+		t.Fatalf("want the file size, got %d", dataset.SizeBytes)
+	}
+	if len(store.put) != 1 {
+		t.Fatalf("want the raster stored once, got %v", store.put)
+	}
+	if len(jobs.converted) != 1 || jobs.converted[0] != dataset.ID {
+		t.Fatalf("want a convert job for %s, got %v", dataset.ID, jobs.converted)
+	}
+}
+
+func TestDatasetService_CreateRasterFromFile_MissingFile(t *testing.T) {
+	svc := newDatasetService(newStubDatasetRepo(), newStubStore(), true)
+	_, err := svc.CreateRasterFromFile(context.Background(), CreateRasterInput{
+		CategoryID: uuid.New(),
+		Filename:   "missing.tif",
+		Path:       filepath.Join(t.TempDir(), "missing.tif"),
+	})
+	if err == nil {
+		t.Fatal("want an error for a missing file")
+	}
+}
--- a/internal/transport/http/dataset_group_handler.go
+++ b/internal/transport/http/dataset_group_handler.go
@@ -0,0 +1,236 @@
+package http
+
+import (
+	"io"
+	"net/http"
+	"strings"
+
+	"gis/internal/domain"
+	"gis/internal/service"
+	"gis/pkg/httputil"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/go-playground/validator/v10"
+)
+
+// DatasetGroupHandler serves the /dataset-groups routes.
+type DatasetGroupHandler struct {
+	svc      *service.DatasetGroupService
+	validate *validator.Validate
+}
+
+// NewDatasetGroupHandler returns a DatasetGroupHandler.
+func NewDatasetGroupHandler(svc *service.DatasetGroupService, validate *validator.Validate) *DatasetGroupHandler {
+	return &DatasetGroupHandler{svc: svc, validate: validate}
+}
+
+// Register mounts the dataset-group routes on r.
+func (h *DatasetGroupHandler) Register(r chi.Router) {
+	r.Get("/", h.list)
+	r.Post("/", h.create)
+	r.Get("/{id}", h.get)
+	r.Put("/{id}", h.update)
+	r.Delete("/{id}", h.delete)
+	r.Get("/{id}/latest", h.latest)
+	r.Post("/{id}/sld", h.uploadSLD)
+	r.Get("/{id}/sld", h.downloadSLD)
+}
+
+type datasetGroupRequest struct {
+	Code        string `json:"code" validate:"required,max=255,slug"`
+	Name        string `json:"name" validate:"required,max=255"`
+	Description string `json:"description" validate:"max=2000"`
+}
+
+func (r datasetGroupRequest) toInput() service.DatasetGroupInput {
+	return service.DatasetGroupInput{Code: r.Code, Name: r.Name, Description: r.Description}
+}
+
+func (h *DatasetGroupHandler) create(w http.ResponseWriter, r *http.Request) {
+	req, err := httputil.DecodeJSON[datasetGroupRequest](w, r)
+	if err != nil {
+		httputil.WriteError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if err := h.validate.Struct(req); err != nil {
+		httputil.WriteValidationErrors(w, err)
+		return
+	}
+
+	group, err := h.svc.Create(r.Context(), req.toInput())
+	if err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	httputil.WriteJSON(w, http.StatusCreated, group)
+}
+
+func (h *DatasetGroupHandler) list(w http.ResponseWriter, r *http.Request) {
+	var code *string
+	if v := strings.TrimSpace(r.URL.Query().Get("code")); v != "" {
+		code = &v
+	}
+
+	page, ok := parsePositiveIntQuery(w, r, "page", 1)
+	if !ok {
+		return
+	}
+	pageSize, ok := parsePositiveIntQuery(w, r, "page_size", service.DefaultPageSize)
+	if !ok {
+		return
+	}
+
+	result, err := h.svc.List(r.Context(), code, page, pageSize)
+	if err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	httputil.WriteJSON(w, http.StatusOK, newPaginated(result.Items, result.Page, result.PageSize, result.Total))
+}
+
+func (h *DatasetGroupHandler) get(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseUUIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	group, err := h.svc.Get(r.Context(), id)
+	if err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	httputil.WriteJSON(w, http.StatusOK, group)
+}
+
+func (h *DatasetGroupHandler) update(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseUUIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	req, err := httputil.DecodeJSON[datasetGroupRequest](w, r)
+	if err != nil {
+		httputil.WriteError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if err := h.validate.Struct(req); err != nil {
+		httputil.WriteValidationErrors(w, err)
+		return
+	}
+
+	group, err := h.svc.Update(r.Context(), id, req.toInput())
+	if err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	httputil.WriteJSON(w, http.StatusOK, group)
+}
+
+// delete removes a group. A group still referenced by datasets yields 409.
+func (h *DatasetGroupHandler) delete(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseUUIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	if err := h.svc.Delete(r.Context(), id); err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// latest returns the freshest dataset of the group (greatest end_date, NULLs
+// last, then newest), optionally narrowed by ?status= and ?file_type=.
+func (h *DatasetGroupHandler) latest(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseUUIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+
+	var status *string
+	if v := strings.TrimSpace(r.URL.Query().Get("status")); v != "" {
+		if !domain.ValidDatasetStatus(v) {
+			httputil.WriteError(w, http.StatusBadRequest, "invalid status")
+			return
+		}
+		status = &v
+	}
+
+	var fileType *domain.FileType
+	if v := strings.TrimSpace(r.URL.Query().Get("file_type")); v != "" {
+		ft := domain.FileType(v)
+		if !ft.Valid() {
+			httputil.WriteError(w, http.StatusBadRequest, "file_type must be one of: vector_with_kato, vector, raster")
+			return
+		}
+		fileType = &ft
+	}
+
+	dataset, err := h.svc.Latest(r.Context(), id, status, fileType)
+	if err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	httputil.WriteJSON(w, http.StatusOK, dataset)
+}
+
+func (h *DatasetGroupHandler) uploadSLD(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseUUIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	if err := r.ParseMultipartForm(maxUploadBytes); err != nil {
+		httputil.WriteError(w, http.StatusBadRequest, "request must be multipart/form-data")
+		return
+	}
+
+	file, header, err := r.FormFile("file")
+	if err != nil {
+		httputil.WriteError(w, http.StatusBadRequest, "file is required")
+		return
+	}
+	defer file.Close()
+
+	contentType := header.Header.Get("Content-Type")
+	if contentType == "" {
+		contentType = "application/xml"
+	}
+
+	group, err := h.svc.UploadSLD(r.Context(), id, service.UploadSLDInput{
+		Filename:    header.Filename,
+		ContentType: contentType,
+		Size:        header.Size,
+		Reader:      file,
+	})
+	if err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	httputil.WriteJSON(w, http.StatusOK, group)
+}
+
+func (h *DatasetGroupHandler) downloadSLD(w http.ResponseWriter, r *http.Request) {
+	id, ok := parseUUIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	group, obj, err := h.svc.DownloadSLD(r.Context(), id)
+	if err != nil {
+		respondDomainError(w, err)
+		return
+	}
+	defer obj.Close()
+
+	contentType := "application/xml"
+	if group.SldContentType != nil && *group.SldContentType != "" {
+		contentType = *group.SldContentType
+	}
+	filename := "style.sld"
+	if group.SldFilename != nil && *group.SldFilename != "" {
+		filename = *group.SldFilename
+	}
+	w.Header().Set("Content-Type", contentType)
+	w.Header().Set("Content-Disposition", `attachment; filename="`+filename+`"`)
+	if _, err := io.Copy(w, obj); err != nil {
+		// Headers are already sent; nothing useful to return to the client.
+		return
+	}
+}
--- a/internal/transport/http/router.go
+++ b/internal/transport/http/router.go
@@ -14,6 +14,8 @@ type RouterDeps struct {
 	Health     *HealthHandler
 	Categories *CategoryHandler
 	Datasets   *DatasetHandler
+	// DatasetGroups serves the /dataset-groups routes.
+	DatasetGroups *DatasetGroupHandler
 	OpenAPISpec   []byte
 }

@@ -37,6 +39,7 @@ func NewRouter(deps RouterDeps) http.Handler {
 	// Domain routes. Add future feature routers here.
 	r.Route("/categories", deps.Categories.Register)
 	r.Route("/datasets", deps.Datasets.Register)
+	r.Route("/dataset-groups", deps.DatasetGroups.Register)

 	return r
 }