Add time properties to PDF File Facet

[ajnelson-nist]

Background

UCO has the ability to represent certain timestamps based on sources like file systems or other metadata fields (e.g. from email). (See #420.) PDFs contain their own specialized timestamp fields, but UCO has no way of representing them yet.

The PDF specification provides for these time stamps:

• CreationDate
• ModDate

Requirements

Requirement 1

UCO must be able to represent the internally embedded creation time of a PDF file.

Requirement 2

UCO must be able to represent the internally embedded modification time of a PDF file.

Requirement 3

UCO must be able to represent the internally embedded access time of a PDF file.

Risk / Benefit analysis

Benefits

UCO would improve its timeline capabilities by representing these times.

Risks

There is a name pattern discrepancy between UCO's current observable:modifiedTime and observable:createdTime, versus the names in the specification. One name pattern must be selected, or the PDF specification should be deferred to.

Otherwise, this is an additive proposal.

Competencies demonstrated

Competency 1

Suppose a PDF is found to have both a creation and modification timestamp embedded.

Competency Question 1.1

Do the creation and modification time follow a sensible temporal ordering - modification occurs at or after creation time?

Ask for all PDF files in our knowledge base that have a creation time that comes definitively after the modification time.

SELECT ?nPdfFile
WHERE {
  ?nPdfFile
    a uco-observable:PDFFile ;
    uco-core:hasFacet ?nPdfFileFacet ;
    .

  ?nPdfFileFacet
    a uco-observable:PDFFileFacet ;
    drafting:pdfCreatedDate ?lCrDate ;
    drafting:pdfModDate ?lModDate ;
    .

  FILTER ( ?lCrDate > ?lModDate )
}

Result 1.1

Solution suggestion

To the observable:PDFFileFacet

• Add property observable:pdfCreatedDate, cardinality 0..1, type xsd:dateTime.
• Add property observable:pdfModDate, cardinality 0..1, type xsd:dateTime.

Coordination

• Tracking in Jira ticket OC-256
• Administrative review completed
• Solutions Approval to be discussed in OC meeting, 2022-08-09
• Solutions Approval vote occurred, passing, on 2022-08-09
• Solutions development phase completed.
• Implementation merged into develop
• Milestone linked
• Documentation logged in pending release page

[ajnelson-nist]

When @eoghanscasey and I were discussing how to name these two properties, we had agreed between us to use the name found in the PDF specification. He had shown me PDF v1.7.

Per that specification, the name we should use is pdfCreationDate, not pdfCreatedDate. See e.g. Table 317 of this document:

https://opensource.adobe.com/dc-acrobat-sdk-docs/standards/pdfstandards/pdf/PDF32000_2008.pdf

found via the Library of Congress format page for PDF, Version 1.7, ISO 32000-1:2008.

CreationDate appears in the PDF specification, not CreatedDate. The implementation of the UCO property will use CreationDate.