Glossary
Terms that appear in PDF Agent Stack's documentation and tool output. Definitions follow the ISO usage wherever the standards define the term.
Terms about the strength of a claim
Keeping these three apart is the design philosophy of the whole of PDF Agent Stack → Architecture & Responsibilities.
| Term | Definition |
|---|---|
| Declaration | A label the file wrote about itself (pdfaid / pdfuaid in XMP: "I am PDF/A"). Writing it is not evidence. This is what the writer's ensure_pdfa / ensure_tagged write |
| Conformance | Whether the file actually meets the standard. There is no way to prove it in full; you can only find where it breaks the rules. Nobody is in a position to state "this conforms" |
| Validation | What a validator (veraPDF and the like) reports against the checks it implements. A pass means "this inspection did not fail", not "the file conforms to the standard" |
| Observation | A fact about what the file contains. Carries no pass/fail (everything the reader returns) |
| Verdict | Pass/fail against a standard or policy (what verify returns). It does not follow automatically from observations |
Assertion strength — T1 / T2 / T3
How strongly a verification result may be stated depends on whether the normative text is at hand. verify's output carries this tier.
| Tier | Standard | How strongly you may speak | Why |
|---|---|---|---|
| T1 | ISO 32000-1/-2, ISO 14289 (PDF/UA) | Quote the clause and state it plainly | In the corpus; the text can be cited |
| T2 | ISO 19005 (PDF/A) | Say only "veraPDF judged this COMPLIANT" | Outside the corpus; the verdict is delegated to veraPDF |
| T3 | ETSI EN 319 142 (PAdES) | Report a structural observation — "structure matching B-LT". Never "conforms" | Outside the corpus, and no third-party validator exists |
T3 reports carry normativeBasis: "T3", making "this is an observation" machine-readable.
basis — the grounds for a rectangle
When the reader returns a rectangle, basis says where the coordinates came from — the mechanism for never returning claims of different strength with the same face (locate_objects / extract_structured_text with include_bbox).
| basis | Meaning | Strength |
|---|---|---|
annotation-rect | The annotation's own /Rect | Exact |
layout-attribute-bbox | The /BBox the file declares (ISO 32000-2 Table 379) | Self-reported, not measured |
text-extent | Measured from the element's text (baseline + ascent/descent = the line box) | Measured, but images and vector art contribute nothing |
page-box | The object is a page; its crop / media box | Exact, but page-grained |
page-content-stream | The object draws the page. The rectangle is the whole page, not the changed part | Coarse |
page-resource | A font, image or other resource. No rectangle exists (rect: null) | Not applicable |
Standards and technical terms
| Term | Definition |
|---|---|
| PAdES | Long-term signature profiles for PDF (ETSI EN 319 142). Four levels: B-B / B-T / B-LT / B-LTA |
| LTV | Long-Term Validation. Stores revocation data in the document so it stays verifiable after the certificates expire |
| DSS | Document Security Store. The dictionary holding LTV validation data (certificates, OCSP, CRL) |
| DocMDP | The permission level of a certification signature (ISO 32000-2 Table 257). P=1 permits nothing / P=2 form fill-in and signing / P=3 additionally annotation operations |
| Incremental update | An update appended to the end of the file (ISO 32000-2 §7.5.6). A legitimate PDF operation — it does not by itself mean tampering |
| Trust anchor | The certificate a signer's chain is evaluated against. Without one, "valid" means only that the cryptography checks out |
| Tagged PDF | A PDF with a structure tree (StructTreeRoot) that makes logical content order and roles machine-readable. The precondition of PDF/UA |
| Artifact | Page decoration outside the logical content (page numbers, running heads). ISO 32000-2 §14.8.2.5 NOTE 3 places it outside reading order. Not the everyday "artifact/deliverable" |
| ActualText | Replacement text for a run of glyphs (ISO 32000-2 §14.9.4). Makes ligatures and hyphenation-fixed words read as they look. Not a description |
| Alt | A description of content that has no text (§14.9.3). Unlike ActualText, it must never be mixed into the body |
| veraPDF | The open-source PDF/A and PDF/UA validator PDF Agent Stack delegates its T2 verdicts to |
Verdict and operational terms
| Term | Definition |
|---|---|
| 4-value verdict | The policy verdict evaluate_policy returns: trust_and_use (usable as-is) / use_with_caution (usable with caveats) / human_review_required / reject. The same facts and profile always yield the same value |
| firedRules | The IDs and reasons of the rules that fired. Use them to explain the outcome, never to override it |
| advisory | A recommendation that does not affect the verdict. Their absence does not mean a pass |
| needs_external_fact | One of validate_clauses' states: a fact outside the file was not supplied, so no decision was made (never defaulted to pass) |
| trace | A failure mark in validate_clauses: the clause binds the PDF processor, so the file shows that someone broke it — not necessarily the last writer |
| indeterminate | Neither disproved nor established. Not the same as "fine" (e.g. verify_integrity's violationAssessment) |
Base vocabulary of this site (AI / engineering)
Not PDF-standard terms, but words this site uses without in-line explanation.
| Term | Definition |
|---|---|
| MCP (Model Context Protocol) | A standard for connecting external tools to AI applications. An MCP server is a program providing capabilities through it |
| Skill | A procedure document an AI agent reads — standardizes tool order, result reading and reporting (also the name of the Claude feature) |
| Deterministic | Same input, same result — always. The counterpart of LLM generation, which is probabilistic and can vary |
| Rule engine | A mechanism that feeds facts through a fixed rule table to produce a verdict automatically. What evaluate_policy is |
| Refutation | Showing one error rather than proving correctness. You cannot prove the file meets the standard; you can only find where it breaks the rules |
| Corpus | The collection of specification originals kept at hand; the ground pdf-spec searches and quotes from |
| Narrative | The explanatory prose. "The judge is code, the narrative is the LLM" = code decides, the LLM only explains |
| Fallback | Switching to an alternative when the primary means is unavailable (e.g. built-in rules when veraPDF is absent) |
| Degraded operation | Continuing with reduced scope when some tools are missing — always labelling the missing items "not performed" |
| Token | The unit in which an LLM processes text (roughly a few characters); the unit of volume and cost |
| Context | The working memory an LLM can read at once. "Wasting context" on this site means this |
| Structured error | A machine-readable error carrying code (kind), next_actions (what to do next) and retryable. Lets an AI recover without guessing at message text |
How to read the diagrams (shape legend)
The structural diagrams (Mermaid) on this site distinguish element kinds by shape.
| Shape | Meaning |
|---|---|
| Rounded | Actor (the AI agent) or end state (delivery, use, …) |
| Hexagon | Skill (procedure & orchestration) |
| Double-framed | MCP server |
| Parallelogram | Input (the PDF under examination, …) |
| Cylinder | External resource (spec corpus, veraPDF) |
| Diamond | Decision / branch |
Related pages
- Architecture & Responsibilities — the four-layer model and assertion strength
- How to Read ISO Specs — telling NOTE, shall and definitions apart