Requirement diagrams

A RequirementDiagram draws requirements and elements linked by relationships, in the style of SysML (Mermaid requirementDiagram):

var diagram = new RequirementDiagram();
var checkout = diagram.AddRequirement("checkout");
checkout.RequirementId = "1";
checkout.Text = "Orders can be paid online.";
checkout.Risk = RequirementRisk.High;
checkout.VerificationMethod = RequirementVerificationMethod.Test;

var payment = diagram.AddRequirement("payment", RequirementKind.FunctionalRequirement);
payment.RequirementId = "1.1";
payment.Text = DiagramText.Markdown("Card payments are **authorized**.");
payment.Risk = RequirementRisk.Medium;
payment.VerificationMethod = RequirementVerificationMethod.Demonstration;

var service = diagram.AddElement("payment_service");
service.Type = "service";
service.DocumentReference = "src/Payments";

diagram.AddRelationship(checkout, payment, RequirementRelationshipKind.Contains);
diagram.AddRelationship(service, payment, RequirementRelationshipKind.Satisfies);

Requirements and elements

A RequirementDiagramRequirement is a box with its Kind (requirement, functional, interface, performance, physical requirement or design constraint) and its name, above its identifier, its text, its Risk and its VerificationMethod. A RequirementDiagramElement is a part of another document, with its type and the reference of the document. The texts can be markdown.

Relationships

A RequirementRelationship shows its kind on the line: contains is a solid line with a circled cross at the source; copies, derives, satisfies, verifies, refines and traces are dashed arrows from the source to the target.

Mermaid syntax

var diagram = (RequirementDiagram)MermaidDocument.Parse("""
    requirementDiagram
        requirement test_req {
            id: 1
            text: the test text.
            risk: high
            verifymethod: test
        }
        element test_entity {
            type: simulation
        }
        test_entity - satisfies -> test_req
    """).Content;

The parser reads the requirements and the elements with their fields, the relationships in both directions (source - satisfies -> target and target <- satisfies - source), direction, classDef, class, :::class and style. The keywords ignore the case, a quoted text is markdown, and # starts a comment. As in Mermaid, the first definition of a name wins, and a relationship to a name that is not defined is ignored, with a warning.