Lightweight Text Assurance Case (LTAC)

The Lightweight Text Assurance Case (LTAC) format can be used to:

  • create assurance case arguments based on data from other systems using scripts, AI tools, or other tools;
  • exchange argument data between applications when the limited scope of information is sufficient;
  • present arguments in text format in a way that is easy for humans to understand.

You can create arguments and argument branches from LTAC text in PREMIS. You can also get LTAC text for your argument or any argument branch.

LTAC Argument Example

Sample LTAC argument is presented below. This text has been inserted into PREMIS and the GSN diagram shown on the right produced.

 
- Claim G1: The system is acceptably safe for operation
  - Context X1: System specification
  - Strategy S1: Argue safety by mitigation of all hazards
    - Claim G2: All hazards have been identified
      - Evidence Ev1: Hazard analysis (HARA report.pdf)
    - Claim G3: All hazards have been mitigated
      - Link Ev1
Assurance argument created from LTAC

LTAC Syntax

  1. The argument is presented in a text format, each argument element in a separate line.
  2. Each line begins with a dash followed by a type keyword, an identifier, a colon ‘:’ and element name
  3. The allowed element type names are: Claim, Strategy, Justification, Evidence, Context and Assumption. These types can be mapped to GSN, CAE and TRUST-IT.
  4. Each LTAC argument starts with a claim. It can contain more than one top claim.
  5. Relationships between elements (such as InContextOf, SupportedBy in GSN) are represented by indentation of two spaces.
  6. Each element should be specified once only. If an element supports or provides context for more than one element, each reuse should be presented by a keyword Link. This represents a citation of the given element. See Link Ev1 in the example argument above.

If you are using AI tools to produce LTAC arguments, you can use the LTAC specification (version 1.1, 6.11.2025). This helps AI tools to provide valid LTAC arguments that can be used in PREMIS.

Final comments

As one of the goals is to let humans easily comprehend LTAC arguments, we keep its format as simple as possible. However some extensions are considered to take place in the future. We will update this page to maintain the current version of LTAC specification here.

If you have any comments or suggestions for changes in LTAC please use our contact form.