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Last modified: September 11, 2000
Graph Exchange Language (GXL)

[September 08, 2000] Following a summer ICSE 2000 Workshop on Standard Exchange Formats (WoSEF, June 06, 2000, Limerick, Ireland), some fourteen research groups working in the domain of software reengineering and graph transformation agreed to collaborative future work on the Graph Exchange Language as a potential standard. These development teams from industry and academic areas committed "to refining GXL to be the standard graph exchange format, write GXL filters and tools or use GXL as exchange format in their tools." Graph Exchange Language (GXL) "is designed to be a standard exchange format for graphs. GXL offers an adaptable and flexible means to support interoperability between graph based tools. In particular, the development of GXL tends to enable interoperability between software reengineering tools and components like code extractors (parsers), analyzers and visualizers. GXL enables software reengineers to combine tools especially designed for special reengineering tasks like parsing, source code extraction, architecture recovery, data flow analysis, pointer analysis, program slicing, query techniques, source code visualization, object recovery, restructuring, refactoring, remodularization etc. into a single powerful reengineering workbench. Being a general graph exchange format, GXL can also be applied to other areas of tool interoperability like interchanging models between CASE tools, or exchanging data between graph transformation or graph visualization tools. GXL has also been designed in such a way that extensions are feasible for handling further kinds of graphs, such as hypergraphs and hierarchical graphs. GXL is a XML sublanguage. The syntax of GXL is given by a XML Document Type Definition. In the current (provisional) design, a gxl document consists of XML elements for describing nodes, edges, attributes. GXL documents can be attributed with a reference to an other GXL document (schema) defining the graph schema and a flag (identifiededges) indicating weather the represented graph requries edges having their own identifiers (this is necessary for graphs having multiple edges). The GXL Metaschema is to reflect the GXL DTD; first attempts at a GXL Metaschema were discussed at WoSEF 2000 in light of a draft proposal ("Components of Interchange Formats - Metaschemas and Typed Graphs"). The structure of graphs exchanged by GXL streams is given by a schema denoted as UML class diagrams which in turn can be exchanged by graphs represented as GXL document. GXL originates in the GRAph eXchange format, GraX (University of Koblenz, DE) for exchanging typed, attributed, ordered directed graphs (TGraphs), combined with the Tuple Attribute Language, TA (University of Waterloo, CA) and the graph format of the PROGRES graph rewriting system (University Bw München, DE). Furthermore GXL includes the exchange format of Relation Partition Algebra, RPA (Philips Research Eindhoven, NL) and Rigi Standard Format, RSF (University of Victoria, CA). Several published papers supply technical description for GXL, including (1) "A Short Introduction to the GXL Exchange Format", (2) "Looking for a Graph eXchange Language", (3) "GXL: Towards a Standard Exchange Format." The project is supported by a GXL mailing list, which is archived.


  • GXL Project Home Page

  • GXL DTD version 0.6.6; text format

  • ICSE 2000 Workshop on Standard Exchange Formats (WoSEF) - "GXL was accepted as a possible standard graph exchange format by numerous research groups working in the domain of software reengineering and graph transformation. The following groups from industry and academics committed to refining GXL to be the standard graph exchange format, write GXL filters and tools or use GXL as exchange format in their tools."

  • GXL Example

  • APPLIGRAPH Subgroup Meeting on Exchange Formats for Graph Transformation - September 5 - 6, 2000. Paderborn University, Germany. 'As a preparation for this meeting, there are already several proposals for a common exchange format for graphs and/or graph transformation systems based on XML.'

  • GXL presentation for APPLIGRAPH meeting [alt URL]

  • See: Barcelona Proposal for graph transformation based on XML. By Gabriel Valiente. "The need for a common exchange format for graph transformation based on XML has been a major conclusion of the panel on the perspectives of graph transformation that took place during the Joint APPLIGRAPH and GETGRATS Workshop on Graph Transformation Systems, held in Berlin in March 2000. The main design goal of the present Barcelona Proposal is simplicity. As will (hopefully) become clear from the discussion below, taking, say, the minimum common XML data supermodel for all existing graph transformation systems and taking also future graph transformation systems (will ever GRACE get incarnation) as well as future uses into account, is perhaps too ambitious a goal to be reached in the short or mid term. The maximum common XML data submodel for all existing graph transformation systems could be adopted instead, agreeing upon those features (elements and attributes) considered to be essential and leaving out additional features which, although important for particular applications, are not essential from the point of view of software exchange within the graph transformation community. The XML data model proposed as exchange format for graph transformation is described in the sequel in a literate programming style, combining code and documentation. In its simplest form, a graph transformation system consists of zero or more graphs followed by zero or more graph transformation rules."

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