The Graph Modeling Language (
GML) (which is
used by Graphlet) has a simple and orthogonal syntax.
A
GML file consists of key-value pairs. Values can be integers,
floats, strings, and lists. Integers are restricted to 32 bit and
floats are double precision. A list consists of key-value pairs.
Duplicate keys within the same list are legal and it is guaranteed
that the order of these duplicates is preserved during reading and
writing. This makes it possible to represent array and list data
structures.
GML has predefined keys like 'graph', 'node', and
'edge'. A graph is represented with the top-level key
'graph', whose value is a list that contains 'node' and
'edge' keys. Every node must be given a unique integer id. The id is
then used to represent edges between two nodes.
GML defines default
values for every data type. These defaults are then used for missing
key-value pairs. Keys unknown to
GML are handled differently,
depending if the key is considered safe or unsafe. Unknown keys that
are safe are considered invariant to graph modification and hence are
ignored (i.e., written back unmodified). In contrast, unsafe keys are
deleted (i.e., not written back) if the tools cannot update them
properly. Safe and unsafe attributes are distinguished with the
following convention: Safe (unsafe) attributes start with a lower (an
upper) case letter.
The following gives a code example that contains two nodes (called
'one' and 'two') that are connected with an edge. The edge is colored
red.
graph [
node [ id 1
label "one" ]
node [ id 2
label "two" ]
edge [ source 1
target 2
graphics [ fill "red" ]
]
]
(Quoted from
ExchangeFormatBibliography)
The Graphlet home page is located at:
The following page describes the
GML format:
--
HolgerKienle