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// Copyright ©2020 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package rdf_test
import (
"fmt"
"log"
"strings"
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/encoding"
"gonum.org/v1/gonum/graph/encoding/dot"
"gonum.org/v1/gonum/graph/formats/rdf"
"gonum.org/v1/gonum/graph/multi"
)
// foodNode implements graph.Node, dot.Node and encoding.Attributer
// to allow the RDF term value to be given to the DOT encoder.
type foodNode struct {
rdf.Term
}
func (n foodNode) DOTID() string {
text, _, kind, err := n.Term.Parts()
if err != nil {
return fmt.Sprintf("error:%s", n.Term.Value)
}
switch kind {
case rdf.Blank:
return n.Term.Value
case rdf.IRI:
return text
case rdf.Literal:
return fmt.Sprintf("%q", text)
default:
return fmt.Sprintf("invalid:%s", n.Term.Value)
}
}
func (n foodNode) Attributes() []encoding.Attribute {
_, qual, _, err := n.Term.Parts()
if err != nil {
return []encoding.Attribute{{Key: "error", Value: err.Error()}}
}
if qual == "" {
return nil
}
parts := strings.Split(qual, ":")
return []encoding.Attribute{{Key: parts[0], Value: parts[1]}}
}
// foodLine implements graph.Line and encoding.Attributer to
// allow the line's RDF term value to be given to the DOT
// encoder and for the nodes to be shimmed to the foodNode
// type.
//
// It also implements line reversal for the semantics of
// a food web with some taxonomic information.
type foodLine struct {
*rdf.Statement
}
func (l foodLine) From() graph.Node { return foodNode{l.Subject} }
func (l foodLine) To() graph.Node { return foodNode{l.Object} }
func (l foodLine) ReversedLine() graph.Line {
if l.Predicate.Value == "<tax:is>" {
// This should remain unreversed, so return as is.
return l
}
s := *l.Statement
// Reverse the line end points.
s.Subject, s.Object = s.Object, s.Subject
// Invert the semantics of the predicate.
switch s.Predicate.Value {
case "<eco:eats>":
s.Predicate.Value = "<eco:eaten-by>"
case "<eco:eaten-by>":
s.Predicate.Value = "<eco:eats>"
case "<tax:is-a>":
s.Predicate.Value = "<tax:includes>"
case "<tax:includes>":
s.Predicate.Value = "<tax:is-a>"
default:
panic("invalid predicate")
}
// All IDs returned by the RDF parser are positive, so
// sign reverse the edge ID to avoid any collisions.
s.Predicate.UID *= -1
return foodLine{&s}
}
func (l foodLine) Attributes() []encoding.Attribute {
text, _, _, err := l.Predicate.Parts()
if err != nil {
return []encoding.Attribute{{Key: "error", Value: err.Error()}}
}
parts := strings.Split(text, ":")
return []encoding.Attribute{{Key: parts[0], Value: parts[1]}}
}
// expand copies src into dst, adding the reversal of each line if it is
// distinct.
func expand(dst, src *multi.DirectedGraph) {
it := src.Edges()
for it.Next() {
lit := it.Edge().(multi.Edge)
for lit.Next() {
l := lit.Line()
r := l.ReversedLine()
dst.SetLine(l)
if l == r {
continue
}
dst.SetLine(r)
}
}
}
func ExampleStatement_ReversedLine() {
const statements = `
_:wolf <tax:is-a> _:animal .
_:wolf <tax:is> "Wolf"^^<tax:common> .
_:wolf <tax:is> "Canis lupus"^^<tax:binomial> .
_:wolf <eco:eats> _:sheep .
_:sheep <tax:is-a> _:animal .
_:sheep <tax:is> "Sheep"^^<tax:common> .
_:sheep <tax:is> "Ovis aries"^^<tax:binomial> .
_:sheep <eco:eats> _:grass .
_:grass <tax:is-a> _:plant .
_:grass <tax:is> "Grass"^^<tax:common> .
_:grass <tax:is> "Lolium perenne"^^<tax:binomial> .
_:grass <tax:is> "Festuca rubra"^^<tax:binomial> .
_:grass <tax:is> "Poa pratensis"^^<tax:binomial> .
`
// Decode the statement stream and insert the lines into a multigraph.
g := multi.NewDirectedGraph()
dec := rdf.NewDecoder(strings.NewReader(statements))
for {
l, err := dec.Unmarshal()
if err != nil {
break
}
// Wrap the line with a shim type to allow the RDF values
// to be passed to the DOT marshaling routine.
g.SetLine(foodLine{l})
}
h := multi.NewDirectedGraph()
expand(h, g)
// Marshal the graph into DOT.
b, err := dot.MarshalMulti(h, "food web", "", "\t")
if err != nil {
log.Fatal(err)
}
fmt.Printf("%s\n\n", b)
// Output:
//
// digraph "food web" {
// // Node definitions.
// "_:wolf";
// "_:animal";
// "Wolf" [tax=common];
// "Canis lupus" [tax=binomial];
// "_:sheep";
// "Sheep" [tax=common];
// "Ovis aries" [tax=binomial];
// "_:grass";
// "_:plant";
// "Grass" [tax=common];
// "Lolium perenne" [tax=binomial];
// "Festuca rubra" [tax=binomial];
// "Poa pratensis" [tax=binomial];
//
// // Edge definitions.
// "_:wolf" -> "_:animal" [tax="is-a"];
// "_:wolf" -> "Wolf" [tax=is];
// "_:wolf" -> "Canis lupus" [tax=is];
// "_:wolf" -> "_:sheep" [eco=eats];
// "_:animal" -> "_:wolf" [tax=includes];
// "_:animal" -> "_:sheep" [tax=includes];
// "_:sheep" -> "_:wolf" [eco="eaten-by"];
// "_:sheep" -> "_:animal" [tax="is-a"];
// "_:sheep" -> "Sheep" [tax=is];
// "_:sheep" -> "Ovis aries" [tax=is];
// "_:sheep" -> "_:grass" [eco=eats];
// "_:grass" -> "_:sheep" [eco="eaten-by"];
// "_:grass" -> "_:plant" [tax="is-a"];
// "_:grass" -> "Grass" [tax=is];
// "_:grass" -> "Lolium perenne" [tax=is];
// "_:grass" -> "Festuca rubra" [tax=is];
// "_:grass" -> "Poa pratensis" [tax=is];
// "_:plant" -> "_:grass" [tax=includes];
// }
}
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