Export lineage as GraphML

Serializes a lineage object to GraphML, the XML graph format read by igraph, Gephi, yEd, and most other graph tools. Each table column becomes a node (id "table.column", duplicated in a name attribute so igraph picks it up as the vertex name) with table, column, and node_type attributes; each column-level edge becomes a directed edge. That granularity is what makes the export useful downstream: igraph::subcomponent(g, "output.total", mode = "in") lists every source column feeding an output, and Gephi can color the graph by table.

Usage

lineage_graphml(lineage, path = NULL)

Arguments

lineage

The result of extract_lineage(), or any list with nodes and edges built with create_table_node() and create_column_edge().

path

Optional file to write the GraphML to. When supplied, the string is returned invisibly.

Value

A string containing the GraphML document.

See also

extract_lineage() to compute lineage automatically

Other lineage exporters: lineage_json()

Examples

lineage <- list(
  nodes = list(
    create_table_node("orders", c("order_id", "amount")),
    create_table_node("daily_totals", "total", table_type = "target")
  ),
  edges = list(
    create_column_edge("orders", "amount", "daily_totals", "total")
  )
)
cat(lineage_graphml(lineage))
#> <?xml version="1.0" encoding="UTF-8"?>
#> <graphml xmlns="http://graphml.graphdrawing.org/xmlns"
#>          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
#>          xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
#>   <key id="name" for="node" attr.name="name" attr.type="string"/>
#>   <key id="table" for="node" attr.name="table" attr.type="string"/>
#>   <key id="column" for="node" attr.name="column" attr.type="string"/>
#>   <key id="node_type" for="node" attr.name="node_type" attr.type="string"/>
#>   <graph id="lineage" edgedefault="directed">
#>     <node id="orders.order_id">
#>       <data key="name">orders.order_id</data>
#>       <data key="table">orders</data>
#>       <data key="column">order_id</data>
#>       <data key="node_type">source</data>
#>     </node>
#>     <node id="orders.amount">
#>       <data key="name">orders.amount</data>
#>       <data key="table">orders</data>
#>       <data key="column">amount</data>
#>       <data key="node_type">source</data>
#>     </node>
#>     <node id="daily_totals.total">
#>       <data key="name">daily_totals.total</data>
#>       <data key="table">daily_totals</data>
#>       <data key="column">total</data>
#>       <data key="node_type">target</data>
#>     </node>
#>     <edge source="orders.amount" target="daily_totals.total"/>
#>   </graph>
#> </graphml>

# Round-trip through igraph for ancestry queries
path <- tempfile(fileext = ".graphml")
lineage_graphml(lineage, path = path)
g <- igraph::read_graph(path, format = "graphml")
igraph::subcomponent(g, "daily_totals.total", mode = "in")
#> + 2/3 vertices, named, from 08a7592:
#> [1] daily_totals.total orders.amount