# 3.1.14. Rule¶

## 3.1.14.1. Class Rule¶

class mod.Rule

Model of a transformation rule in the Double Pushout formalism.

id

(Read-only) The unique instance id among all Rule instances.

Type: unsigned int
numVertices

(Read-only) The number of vertices in the rule.

Type: int
vertices

(Read-only) An iterable of all vertices in the rule.

Type: RuleVertexRange
numEdges

(Read-only) The number of edges in the rule.

Type: int
edges

(Read-only) An iterable of all edges in the rule.

Type: RuleEdgeRange
left

(Read-only) A proxy object representing the left graph of the rule.

context

(Read-only) A proxy object representing the context graph of the rule.

right

(Read-only) A proxy object representing the right graph of the rule.

makeInverse()
Returns: a rule representing the inversion of this rule. Rule InputError if inversion is not possible (due to matching constraints).
print()
print(first, second=None)

Print the rule, using either the default options or the options in first and second. If first and second are the same, only one depiction will be made.

Parameters: first (GraphPrinter) – the printing options used for the first depiction. second (GraphPrinter) – the printing options used for the second depiction. If it is None then it is set to first. a pair of filename prefixes for the PDF-files that will be compiled in post-processing. The actual names can be obtained by appending _L.pdf, _K.pdf, and _R.pdf for respectively the left side, context, and right side graphs. If first and second are the same, the two file prefixes are equal. (string, string)
getGMLString(withCoords=False)
Returns: the GML representation of the rule, optionally with generated 2D coordinates. string LogicError when coordinates are requested, but none can be generated.
printGML(withCoords=False)

Print the rule in GML format, optionally with generated 2D coordinates.

Returns: the filename of the printed GML file. string LogicError when coordinates are requested, but none can be generated.
name

The name of the rule. The default name includes the unique instance id.

Type: string
numLeftComponents

(Read-only) The number of connected components of the left graph.

Type: std::size_t
numRightComponents

(Read-only) The number of connected components of the right graph.

Type: std::size_t
isomorphism(other, maxNumMatches=1)
Parameters: other (Rule) – the other Rule for comparison. maxNumMatches (std::size_t) – the maximum number of isomorphisms to search for. the number of isomorphisms found between other and this rule, but at most maxNumMatches. std::size_t
monomorphism(host, maxNumMatches=1)
Parameters: host (Rule) – the host Rule to check for subgraphs. maxNumMatches (std::size_t) – the maximum number of morphisms to search for. the number of monomorphisms from this rule to subgraphs of host, though at most maxNumMatches. std::size_t
mod.ruleGMLString(s, invert=False)

Load a rule from a GML string, and store either that rule or its inverse. The name of the rule is the one specified in the GML string, though when invert=True the string ”, inverse” is appended to the name.

Note

If the GML string specifies matching constraints it is not possible to invert the rule. There is however a configuration option to ignore matching constraints when inverting rules.

Parameters: s (string) – the GML string to load a rule from. invert (bool) – whether or not to invert the loaded rule. the rule in the GML string, possibly inverted. Rule
mod.ruleGML(s, invert=False)

Read file and pass the contents to ruleGMLString().

Parameters: s (string) – name of the GML file to be loaded. invert (bool) – whether or not to invert the loaded rule. the rule in the GML file, possibly inverted. Rule