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.
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.
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:
Element type | Description |
---|---|
Address | A text element for capturing physical addresses. |
EmailAddress | A text element for capturing email addresses. |
FigureCaption | An element for capturing text associated with figure captions. |
Footer | An element for capturing document footers. |
Formula | An element containing formulas in a file. |
Header | An element for capturing document headers. |
Image | A text element for capturing image metadata. |
ListItem | ListItem is a NarrativeText element that is part of a list. |
NarrativeText | NarrativeText is an element consisting of multiple, well-formulated sentences. This excludes elements such titles, headers, footers, and captions. |
PageBreak | An element for capturing page breaks. |
Table | An element for capturing tables. |
Title | A text element for capturing titles. |
UncategorizedText | Base element for capturing free text from within files. |
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.
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.
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.
Common metadata fields
All file types return the following metadata
fields when the information is available from the source file:
Metadata field name | Description |
---|---|
category_depth | The depth of the element relative to other elements of the same category. Category depth is the depth of an element relative to other elements of the same category. It is set by a file partitioner and enables the document hierarchy after processing to compute more accurate hierarchies. Category depth might be set using native document hierarchies, for example reflecting <H1> or <H2> tags within an HTML file or the indentation level of a bulleted list item in a Word document. |
coordinates | Any X-Y bounding box coordinates. |
detection_class_prob | The detection model class probabilities. Applies only to Unstructured inference using the High Res strategy. |
emphasized_text_contents | The related emphasized text (bold or italic) in the original file. |
emphasized_text_tags | Any tags on the text that are emphasized in the original file. |
file_directory | The related file’s directory. |
filename | The related file’s filename. |
filetype | The related file’s type. |
is_continuation | True if the element is a continuation of a previous element. Only relevant for chunking, if an element was divided into two due to Max Characters. |
languages | Document languages at the file or element level. The list is ordered by probability of being the primary language of the text. |
last_modified | The related file’s last modified date. |
parent_id | The ID of the element’s parent element. parent_id might be used to infer where an element resides within the overall document hierarchy. For instance, a NarrativeText element might have a Title element as a parent (a “subtitle”), which in turn might have another Title element as its parent (a “title”). |
text_as_html | The HTML representation of the related extracted table. Only applicable to table elements. |
Notes on common metadata fields:
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.
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 they
coordinate increases in the downward direction.system
: The points have an associated coordinate system. A typical example of a coordinate system isPixelSpace
, which is used for representing the coordinates of images. The coordinate system has a name, orientation, layout width, and layout height.
Additional metadata fields by file type
Field name | Applicable file types | Description |
---|---|---|
page_number | DOCX, PDF, PPT, XLSX | The related file’s page number. |
page_name | XLSX | The related sheet’s name in an Excel file. |
sent_from | EML | The related email sender. |
sent_to | EML | The related email recipient. |
subject | EML | The related email subject. |
attached_to_filename | MSG | The name of the file that the attached file is attached to. |
header_footer_type | Word Doc | The pages that a header or footer applies to in a Word document: primary , even_only , and first_page . |
link_urls | HTML | The URL that is associated with a link in a document. |
link_texts | HTML | The text that is associated with a link in a document. |
section | EPUB | The book section title corresponding to a table of contents. |
Here are some notes on additional metadata fields by file type:
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.
Microsoft Excel files
For Excel files, metadata will contain a page_name
element, which corresponds to the sheet name in the Excel
file.
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"
.
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>
Data connector metadata fields
Documents can include additional file metadata, based on the specified source connector.
Common data connector metadata fields
date_created
date_modified
date_processed
record_locator
url
version
Additional metadata fields by connector type (within record_locator)
Source connector | Additional metadata |
---|---|
Azure | protocol , remote_file_path |
Elasticsearch | document_id , index_name , url |
Google Drive | drive_id , file_id |
OneDrive | server_relative_path , user_pname |
S3 | protocol , remote_file_path |
SharePoint | server_path , site_url |
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