Package s3 :: Module s3utils :: Class S3MultiPath

Class S3MultiPath


Simplified path toolkit for managing multi-ancestor-hypergraphs
in a relational database.

MultiPaths allow single-query searches for all ancestors and
descendants of a node, as well as single-query affiliation
testing - whereas they require multiple writes on update (one
per each descendant node), so they should only be used for
hypergraphs which rarely change.

Every node of the hypergraph contains a path attribute, with the
following MultiPath-syntax:

MultiPath: <SimplePath>,<SimplePath>,...
SimplePath: [|<Node>|<Node>|...|]
Node: ID of the ancestor node

SimplePaths contain only ancestors, not the node itself.

SimplePaths contain the ancestors in reverse order, i.e. the nearest
ancestor first (this is important because removing a vertex from the
path will cut off the tail, not the head)

A path like A<-B<-C can be constructed like:

    path = S3MultiPath([["C", "B", "A"]])
    [|C|B|A|]

Extending this path by a vertex E<-B will result in a multipath like:

    path.extend("B", "E")
    [|C|B|A|],[|C|B|E|]

Cutting the vertex A<-B reduces the multipath to:

    path.cut("B", "A")
    [|C|B|E|]

Note the reverse notation (nearest ancestor first)!

MultiPaths will be normalized automatically, i.e.:

    path = S3MultiPath([["C", "B", "A", "D", "F", "B", "E", "G"]])
    [|C|B|A|D|F|],[|C|B|E|G|]

Nested Classes
	Path

Instance Methods

__init__(self, paths=None)
Constructor

source code

append(self, path)
Append a new ancestor path to this multi-path

source code

extend(self, head, ancestors=None, cut=None)
Extend this multi-path with a new vertex ancestors<-head

source code

cut(self, head, ancestor=None)
Cut off the vertex ancestor<-head in this multi-path

source code

clean(self)
Remove any duplicate and empty paths from this multi-path

source code

__repr__(self)
Serialize this multi-path as string

source code

as_list(self)
Return this multi-path as list of node lists

source code

__len__(self)
The number of paths in this multi-path

source code

__and__(self, sequence)
Check whether sequence is the start sequence of any of the paths in this multi-path (for de-duplication)

source code

__contains__(self, sequence)
Check whether sequence is contained in any of the paths (can also be used to check whether this multi-path contains a path to a particular node)

source code

nodes(self)
Get all nodes from this path

source code

Static Methods

all_nodes(paths)
Get all nodes from all paths

source code

Method Details