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Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

docling/pipeline/base_model_pipeline.py

@@ -6,6 +6,7 @@ from abc import ABC, abstractmethod
 from typing import Callable, Iterable, List
 
 from docling.backend.abstract_backend import AbstractDocumentBackend
+from docling.backend.pdf_backend import PdfDocumentBackend
 from docling.datamodel.base_models import (
     ConversionStatus,
     DoclingComponentType,
@@ -46,7 +47,7 @@ class BaseModelPipeline(ABC):
         pass
 
 
-class PaginatedModelPipeline(BaseModelPipeline):
+class PaginatedModelPipeline(BaseModelPipeline):  # TODO this is a bad name.
 
     def apply_on_pages(self, page_batch: Iterable[Page]) -> Iterable[Page]:
         for model in self.model_pipe:
@@ -59,6 +60,10 @@ class PaginatedModelPipeline(BaseModelPipeline):
 
         _log.info(f"Processing document {in_doc.file.name}")
 
+        if not isinstance(in_doc._backend, PdfDocumentBackend):
+            conv_res.status = ConversionStatus.FAILURE
+            return conv_res
+
         for i in range(0, in_doc.page_count):
             conv_res.pages.append(Page(page_no=i))
 
@@ -75,7 +80,7 @@ class PaginatedModelPipeline(BaseModelPipeline):
                 # 2. Run pipeline stages
                 pipeline_pages = self.apply_on_pages(init_pages)
 
-                for p in pipeline_pages:
+                for p in pipeline_pages:  # Must exhaust!
                     pass
 
                 end_pb_time = time.time() - start_pb_time

docling/pipeline/simple_model_pipeline.py

@@ -16,6 +16,11 @@ _log = logging.getLogger(__name__)
 
 
 class SimpleModelPipeline(BaseModelPipeline):
+    """SimpleModelPipeline.
+
+    This class is used at the moment for formats / backends
+    which produce straight DoclingDocument output.
+    """
 
     def __init__(self, pipeline_options: PdfPipelineOptions):
         super().__init__(pipeline_options)
@@ -33,6 +38,10 @@ class SimpleModelPipeline(BaseModelPipeline):
             conv_res.status = ConversionStatus.FAILURE
             return conv_res
 
+        # Instead of running a page-level pipeline to build up the document structure,
+        # the backend is expected to be of type DeclarativeDocumentBackend, which can output
+        # a DoclingDocument straight.
+
         conv_res.experimental = in_doc._backend.convert()
 
         # Do other stuff with conv_res.experimental