4.1.8.1. dg/Builder

class mod.DGBuilder

An RAII-style object obtained from DG.build(). On destruction of an active builder object the owning DG will be locked for further modifications.

The object can be used as a context manager:

dg = DG()
with dg.build() as b:
    # b is a DGBuilder
# b has now been destructed and dg is locked.

Otherwise one can manually use del on the obtained builder to trigger the destruction.

dg

The derivation graph this builder can modify.

Type:

DG

isActive

Whether this object is associated with a DG.

Type:

bool

addDerivation(d, graphPolicy=IsomorphismPolicy.Check)

Adds a hyperedge corresponding to the given derivation to the associated DG. If it already exists, only add the given rules to the edge.

Parameters:

  • d (Derivations) – a derivation to add a hyperedge for.

  • graphPolicy (IsomorphismPolicy) – the isomorphism policy for adding the given graphs.

Returns:

the hyperedge corresponding to the given derivation.

Return type:

DGHyperEdge

Raises:

LogicError if d.left or d.right is empty.

Raises:

LogicError if a None``is in ``d.left, d.right, or d.rules.

Raises:

LogicError if graphPolicy == IsomorphismPolicy.Check and a given graph object is different but isomorphic to another given graph object or to a graph object already in the internal graph database in the associated derivation graph.

addHyperEdge(e, graphPolicy=IsomorphismPolicy.Check)

Adds a hyperedge to the associated DG from a copy of the given hyperedge (from a different DG). If it already exists, only add the rules to the edge.

Parameters:
Returns:

the hyperedge corresponding to the copy of the given hyperedge.

Return type:

DGHyperEdge

Raises:

LogicError if e is a null edge.

Raises:

LogicError if graphPolicy == IsomorphismPolicy.Check and a given graph object is different but isomorphic to another given graph object or to a graph object already in the internal graph database in the associated derivation graph.

execute(strategy, *, verbosity=2, ignoreRuleLabelTypes=False)

Execute the given strategy (Derivation Graph Strategies) and as a side effect add vertices and hyperedges to the underlying derivation graph.

Parameters:

  • strategy (DGStrat) – the strategy to execute.

  • verbosity (int) – the level of verbosity of printed information during calculation. See dg::Builder::execute() for explanations of the levels.

  • ignoreRuleLabelTypes (bool) – whether rules in the strategy should be checked beforehand for whether they have an associated LabelType which matches the one in the underlying derivation graph.

Returns:

a proxy object for accessing the result of the execution.

Return type:

DGExecuteResult

Throws:

LogicError if a static “add” strategy has IsomorphismPolicy.Check as graph policy, and it tries to add a graph object isomorphic to an already known, but different, graph object in the database. This is checked before execution, so there is strong exception guarantee.

Throws:

LogicError if a dynamic “add” strategy has IsomorphismPolicy.Check as graph policy, and it tries to add a graph object isomorphic to an already known, but different, graph object in the database.

Warning

This is checked during execution, so while the basic exception guarantee is provided, there may be modifications to the underlying derivation graph.

Throws:

LogicError if a dynamic “add” strategy is executed where a returned graph is None.

Warning

This is checked during execution, so while the basic exception guarantee is provided, there may be modifications to the underlying derivation graph.

Throws:

LogicError: if ignoreRuleLabelTypes is False, which is the default, and a rule in the given strategy has an associated LabelType which is different from the one in the derivation graph.

apply(graphs, r, onlyProper=True, verbosity=0, graphPolicy=IsomorphismPolicy.Check)

Compute direct derivations.

Parameters:

  • graphs (list[Graph]) – the graphs constituting the left-hand side of the computed direct derivations.

  • onlyProper (bool) – when True, then all of graphs must be used in each direct derivation.

  • r (Rule) – the rule to use for the direct derivations.

  • verbosity (int) – the level of verbosity of printed information during calculation. See dg::Builder::apply() for explanations of the levels.

  • graphPolicy (IsomorphismPolicy) – the isomorphism policy for adding the given graphs.

Returns:

a list of hyper edges representing the found direct derivations. The list may contain duplicates if there are multiple ways of constructing the same direct derivation when ignoring the specific match morphism.

Return type:

list[DGHyperEdge]

Raises:

LogicError if there is a None in graphs.

Raises:

LogicError if r is None.

Raises:

LogicError if graphPolicy == IsomorphismPolicy.Check and a given graph object is different but isomorphic to another given graph object or to a graph object already in the internal graph database in the associated derivation graph.

addAbstract(description)

Add vertices and hyperedges based on the given abstract description. The description must adhere to the grammar described at Abstract Derivation Graphs.

For each vertex named in the description a graph object with a single vertex will be created. The label of that vertex and the name of the graph is set to the given identifier.

Parameters:

description (str) – the description to parse into abstract derivations.

Raises:

InputError if the description could not be parsed.

load(ruleDatabase, f, verbosity=2)

Load and add a derivation graph dump. Use DG.load() to load a dump as a locked derivation graph.

The label settings of this DG and the ones retrieved from the dump file must match. Vertices with graphs and hyperedges with rules are then added from the dump. Any graph in the dump which is isomorphic to a graph in the internal graph database of the DG is replaced by the given graph. The same procedure is done for the rules, but compared against the given rules. If a graph/rule is not found in the given lists, a new object is instantiated and used.

See dg::DG::load() for an explanation of the verbosity levels.

Parameters:

  • ruleDatabase (list[Rule]) – A list of rules used as explained above.

  • f (str or CWDPath) – a DG dump file to load.

Raises:

LogicError if there is a None in ruleDatabase.

Raises:

LogicError if the label settings of the dump does not match those of this DG. :raises: InputError if the file can not be opened or its content is bad.

class mod.DGExecuteResult

The result from calling DGBuilder.execute().

subset
universe

(Read-only) Respectively the subset and the universe computed by the strategy execution (see also Derivation Graph Strategies).

Type:

list[Graph]

list(*, withUniverse=False)

Output information from the execution of the strategy.

Parameters:

withUniverse (bool) – The universe lists can be rather long. As default, they are omitted when listing.