Document elements and metadata

When Unstructured partitions a file, the result is a list of document elements, sometimes referred to simply as elements. These elements represent different components of the source file.

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Element example

Here’s an example of what an element might look like:

{
    "type": "NarrativeText",
    "element_id": "5ef1d1117721f0472c1ad825991d7d37",
    "text": "The Unstructured documentation covers the following services:",
    "metadata": {
        "last_modified": "2024-05-01T14:15:22",
        "page_number": 1,
        "languages": ["eng"],
        "parent_id": "56f24319ae258b735cac3ec2a271b1d9",
        "file_directory": "/content",
        "filename": "Unstructured documentation.html",
        "filetype": "text/html"
    }
}

Every element has a type; an element_id; the extracted text; and some metadata which might vary depending on the element type, file structure, and some additional settings that are applied during partitioning, chunking, summarizing, and embedding.

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Element type

Instead of treating all files as strings of plain text, Unstructured preserves the semantic structure of the files. This gives you more control and flexibility over how you further use the processed files and allows you to take their structure into consideration. At the same time, normalizing data from various file formats to the Unstructured element type scheme lets you treat all files the same in your downstream processing, regardless of source format. For example, if you plan to summarize a file, you might only be interested in the narrative of the file and not care about its headers and footers. You can easily filter out the elements you don’t need by specifying their type.

Here are some examples of the element types your file might contain:

If you apply chunking, you will also see the CompositeElement type. CompositeElement is a chunk formed from text (non-Table) elements. A composite element might be formed by combining one or more sequential elements produced by partitioning. For example, several individual list items might be combined into a single chunk.

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Element ID

By default, the element ID is a SHA-256 hash of the element’s text, its position on the page, the page number it’s on, and the name of the related file. This is to ensure that the ID is deterministic and unique at the file level.

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Metadata

Unstructured tracks a variety of metadata about the elements extracted from files. Metadata is tracked at the element level within metadata.

Element metadata enables you to do things such as:

• Filter file elements based on an element’s metadata value. For instance, you might want to limit your scope to elements from a certain page, or you might want to use only elements that have an email matching a regular expression in their metadata.
• Map an element to the page where it occurred so that the original page can be retrieved when that element matches search criteria.

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Common metadata fields

All file types return the following metadata fields when the information is available from the source file:

Notes on common metadata fields:

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Document hierarchy

parent_id and category_depth enhance hierarchy detection to identify the document structure in various file formats by measuring relative depth of an element within its category. This is especially useful in files with native hierarchies like HTML or Word files, where elements like headings or list items inherently define structure.

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Element coordinates

Some file types support location data for the elements, usually in the form of bounding boxes.

The coordinates metadata field contains:

• points : These specify the corners of the bounding box starting from the top left corner and proceeding counter-clockwise. The points represent pixels, the origin is in the top left and the y coordinate increases in the downward direction.
• system: The points have an associated coordinate system. A typical example of a coordinate system is PixelSpace, which is used for representing the coordinates of images. The coordinate system has a name, orientation, layout width, and layout height.

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Additional metadata fields by file type

Here are some notes on additional metadata fields by file type:

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Email

Emails will include sent_from, sent_to, and subject metadata. sent_from is a list of strings because the RFC 822 spec for emails allows for multiple sent from email addresses.

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Microsoft Excel files

For Excel files, metadata will contain a page_name element, which corresponds to the sheet name in the Excel file.

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Microsoft Word files

Headers and footers in Word files include a header_footer_type indicating which page a header or footer applies to. Valid values are "primary", "even_only", and "first_page".

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Table-specific metadata

For Table elements, the raw text of the table will be stored in the text attribute for the element, and HTML representation of the table will be available in the element metadata under text_as_html. Unstructured will automatically extract all tables for all doc types if you check the Infer Table Structure in the ConnectorSettings area of the Transform section of a workflow.

Here’s an example of a table element. The text of the element will look like this:

Dataset Base Model1 Large Model Notes PubLayNet [38] F / M M Layouts of modern scientific documents PRImA [3] M - Layouts of scanned modern magazines and scientific reports Newspaper [17] F - Layouts of scanned US newspapers from the 20th century TableBank [18] F F Table region on modern scientific and business document HJDataset [31] F / M - Layouts of history Japanese documents

And the text_as_html metadata for the same element will look like this:

<table><thead><th>Dataset</th><th>| Base Model’</th><th>| Notes</th></thead><tr><td>PubLayNet</td><td>[38] F/M</td><td>Layouts of modern scientific documents</td></tr><tr><td>PRImA [3]</td><td>M</td><td>Layouts of scanned modern magazines and scientific reports</td></tr><tr><td>Newspaper</td><td>F</td><td>Layouts of scanned US newspapers from the 20th century</td></tr><tr><td>TableBank</td><td>F</td><td>Table region on modern scientific and business document</td></tr><tr><td>HJDataset [31]</td><td>F/M</td><td>Layouts of history Japanese documents</td></tr></table>

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Data connector metadata fields

Documents can include additional file metadata, based on the specified source connector.

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Common data connector metadata fields

• date_created
• date_modified
• date_processed
• record_locator
• url
• version

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Additional metadata fields by connector type (within record_locator)