Appendix C — Glossary

Contents of DISL 0.1

Term	Meaning
Axis	A scale from domain values (numbers, timestamps, categories, angles) to canvas distance along one direction.
Band	One category of an ordinal axis, drawn as a lane, row or column.
Bindable	A property that accepts a literal or a dynamic value (`cel`, `attribute`, `token`, `param`).
Bound placement	A coordinate read from and written to a model attribute.
Canvas units	Rendering units at zoom 1; pixels for the default axis.
CEL	Common Expression Language, the only expression language of DISL.
Compartment	A stacked region inside a node listing items.
Context (CEL)	The set of variables available to an expression, determined by where it appears.
DID definition	A diagram a user created of a diagram type, stored as a `.did` file (DID, the Diagram Definition Language).
Document	The content a user works on in a host; for a diagram, its stored form is a DID definition.
Domain value	A position in the units of its axis: a number, a timestamp or a band reference.
Gesture constraint	A constraint evaluated before a user action is applied (connect, contain, create, delete, place, change).
Handle	An interactive point on a shape that edits a shape parameter.
Invariant	A constraint on the current state of the diagram.
Marker	A decoration at an edge end or along an edge, such as an arrowhead.
Metamodel	The abstract syntax: types, attributes, relations, containment and ports.
Notation	The concrete syntax: shapes, styles, labels and markers.
Plugin	Named, declared, versioned code that extends a runtime.
Port	A named connection point on a node.
Runtime	Software in a host that loads a specification and lets users create and change DID definitions with it.
Specification	A DISL file (`.dis`) in which a tool engineer specifies one diagram type.
Tool engineer	The person who specifies a diagram type in DISL.
Snap rule	A function mapping a raw domain value to an allowed value on one axis.
Token	A named theme value (a color, font or size), resolved per theme mode.
Transaction	An atomic, undoable unit of change.
Variant	An alternative notation applied when a condition holds.
View data	Per-diagram placement and presentation data stored separately from the model.
View-only element	An element that exists only in a view (a note or frame) and has no model meaning.
Viewpoint	A kind of diagram over the model, with its own types, coordinates, toolbox and layout.