Hi all,
the implementation of importers for [graph] requires a bit of attention,
in particular with the new model where
* there are no explicit markers for Vertex and Edge,
* all properties of Vertices and Edges are now specified with generic
Mappers.
Writing and extending exporters is fine: we first specify the graph,
then its properties one after the other in a "fluent chain". The
exporter simply forgets about the types of Vertex/Edge and serializes
the whole input. Importing back a graph from an input source, however,
is not as simple because:
* standard file formats give us no indication about Vertex/Edge types;
* serialized graphs come with a number of properties, some of which we
know and sometimes need for graph processing (e.g. labels and
weights), while some others are not (yet?) recognized in the code;
* the return type of any importer should account for both the graph
itself and all the properties.
As a first step, these are my suggestions for the design:
* we need at least default, empty implementations for Vertex and Edge;
together with that, we could do some black magic to allow the user
to specify what types should be used to map imported Vertices/Edges
to actual classes.
* we need a structure to host both the imported graph and properties.
And it should be easy for the user to query such a structure for
specific graph properties, i.e. we need to isolate properties that
we recognize and use in our algorithms (e.g. weights). Other
properties could be either ignored or imported with a reference to
their name in the input format.
One way could be to explicitly ask the user to list all the properties
that he expects from the input graph, raising exceptions if they are not
found. Something like:
* importGraph().asGraphML( "graph1.gml"
).withEdgeWeights().withVertexLabels(); // only two properties
loaded and explicitly identified
* importGraph().asGraphML( "graph2.gml" ).withAllProperties(); // all
properties are loaded, none is explicitly recognized
...wow that was long. What do you [graph]ers think? :)
Ciao,
Claudio
--
Claudio Squarcella
PhD student at Roma Tre University
http://www.dia.uniroma3.it/~squarcel
http://twitter.com/hyperboreans
http://claudio.squarcella.com/
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