swish-0.9.0.7: A semantic web toolkit.

Portability | H98
Stability | experimental
Maintainer | Douglas Burke
Safe Haskell | Safe-Inferred

Swish.GraphPartition

Description

This module contains functions for partitioning a graph into subgraphs that rooted from different subject nodes.

Synopsis

- data PartitionedGraph lb = PartitionedGraph [GraphPartition lb]
- getArcs :: PartitionedGraph lb -> [Arc lb]
- getPartitions :: PartitionedGraph lb -> [GraphPartition lb]
- data GraphPartition lb
  - = PartObj lb
  - | PartSub lb (NonEmpty (lb, GraphPartition lb))
- node :: GraphPartition lb -> lb
- toArcs :: GraphPartition lb -> [Arc lb]
- partitionGraph :: Label lb => [Arc lb] -> PartitionedGraph lb
- comparePartitions :: Label lb => PartitionedGraph lb -> PartitionedGraph lb -> [(Maybe (GraphPartition lb), Maybe (GraphPartition lb))]
- partitionShowP :: Label lb => String -> GraphPartition lb -> String

# Documentation

data PartitionedGraph lb Source

Representation of a graph as a collection of (possibly nested) partitions. Each node in the graph appears at least once as the root value of a `GraphPartition` value:

- Nodes that are the subject of at least one statement appear as the first value of exactly one `PartSub` constructor, and may also appear in any number of `PartObj` constructors.
- Nodes appearing only as objects of statements appear only in `PartObj` constructors.

Constructors

PartitionedGraph [GraphPartition lb] |

Instances

Label lb => Eq (PartitionedGraph lb) |
Label lb => Show (PartitionedGraph lb) |

getArcs :: PartitionedGraph lb -> [Arc lb]Source

Returns all the arcs in the partitioned graph.

getPartitions :: PartitionedGraph lb -> [GraphPartition lb]Source

Returns a list of partitions.

data GraphPartition lb Source

Represent a partition of a graph by a node and (optional) contents.

Constructors

PartObj lb |
PartSub lb (NonEmpty (lb, GraphPartition lb)) |

Instances

Label lb => Eq (GraphPartition lb) | Equality is based on total structural equivalence rather than graph equality.
Label lb => Ord (GraphPartition lb) |
Label lb => Show (GraphPartition lb) |

node :: GraphPartition lb -> lbSource

Returns the node for the partition.

toArcs :: GraphPartition lb -> [Arc lb]Source

Creates a list of arcs from the partition. The empty list is returned for `PartObj`.

partitionGraph :: Label lb => [Arc lb] -> PartitionedGraph lbSource

Turning a partitioned graph into a flat graph is easy. The interesting challenge is to turn a flat graph into a partitioned graph that is more useful for certain purposes. Currently, I'm interested in:

1. isolating differences between graphs
2. pretty-printing graphs

For (1), the goal is to separate subgraphs that are known to be equivalent from subgraphs that are known to be different, such that:

- different sub-graphs are minimized,
- different sub-graphs are placed into 1:1 correspondence (possibly with null subgraphs), and
- only deterministic matching decisions are made.

For (2), the goal is to decide when a subgraph is to be treated as nested in another partition, or treated as a new top-level partition. If a subgraph is referenced by exactly one graph partition, it should be nested in that partition, otherwise it should be a new top-level partition.

Strategy. Examining just subject and object nodes:

- all non-blank subject nodes are the root of a top-level partition
- blank subject nodes that are not the object of exactly one statement are the root of a top-level partition.
- blank nodes referenced as the object of exactly 1 statement of an existing partition are the root of a sub-partition of the refering partition.
- what remain are circular chains of blank nodes not referenced elsewhere: for each such chain, pick a root node arbitrarily.

comparePartitions :: Label lb => PartitionedGraph lb -> PartitionedGraph lb -> [(Maybe (GraphPartition lb), Maybe (GraphPartition lb))]Source

Create a list of pairs of corresponding Partitions that are unequal.

partitionShowP :: Label lb => String -> GraphPartition lb -> String Source

Convert a partition into a string with a leading separator string.