Appendix C — Glossary

Contents of DISL 0.2

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.
Budget	A hard limit on how much of a model a view draws, with what is withheld while it is reached (3.2.1).
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.
Derived element	An element computed from other elements of the model, never stored or written (4.11).
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.
Ephemeral id	An id that identifies an element within one reading of the model only; nothing is stored keyed by it (11.5.3).
Finding	The result of a rule or of reading a model: a severity, a message and what it is about (8.6).
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.
Message	A text a runtime shows to users: a LocalizedText or a CEL value returning one (2.3).
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.
Reason	Why something is refused, read-only or unavailable: a Message, a conditional Message or a named reason (2.3).
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.
Viewer state	View data that belongs to one viewer (folds, filters, the variant shown): never stored, never undone (11.6).
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.