Graph Exchange Language

Universität Koblenz-Landau Institut für Softwaretechnik Re-Group

Graph Exchange Language

Representing Graph Schemas

(a working report)

Ric Holt

Andreas Winter

Contents

Motivation

... summarizing previous talks

GXL schema notation

... using UML class diagrams

Exchanging GXL schemas

... using GXL documents

Conclusion

... previous Talks

Sim:

– WoSEF 2000, CASCON 2000: need for schemas – lone pine schema sanctuary

(http://www.cs.utoronto.ca/~simsuz/schema)

Holt, Hassan, Lague, Lapierre, Leduc (DATRIX):

– AST schemas for C/C++, Java

Boshernitsan, Graham:

– schemas for AST´s on different levels of granularity

Godfrey:

– hierarchy of schemas (different levels of granularity)

Girard et al. (BAUHAUS):

– schema for resource graph (architectural level)

Tichelaar, Ducasse, Demeyer (FAMIX)

– coarse grained, language independent schema for OO

Variety of different schemas

Dimensions

– Programming Languages

• single language systems (Cobol, C, C++, JAVA, ...)

• multi language systems

– Level of Abstraction

• AST level

• architectural level

Requirements

– adaptable and extensible interchange format

GXL Approach

– exchange of schema data and

– exchange of instance data

standard exchange language

– for interchanging data between software engineering tools

• on instance level

• on schema level

mathematical model on instance and schema level – typed, attributed, directed graphs

notation

– eXtensible Markup Language (XML) and Unified Modeling Language (UML)

• graphs: UML object diagrams (yesterday)

• schemas: UML class diagrams (now)

GXL Objective

Example

while x > 0 do repeat

y := y + 1 until (y = x);

x := x + 1

end

What to Represent in a Graph Schema

• node, edge, and relation types

• attribute names and attribute types

• associations

– between node, edge, relation types

– between attributes and node, edge, relation types

• higher conceptual modeling constructs

– generalization of node, edge, and relation types – aggregation

– composition (hierarchical graphs)

• miscellaneous

– edge direction

– constraints e.g. cardinalities

– ordering of incidences

Graph Schema

UML class diagram (schema)

Var

file : string

line : int line : int

refers

Proc

v : Var

file="main.c"

line = 27 line = 42

e : refers

UML object diagram (graph)

p : Proc

Graph Schema - Notation

Var

file : string

line : int line : int

refers

Proc

edge type

node type node attribute

ordering

{ordered}

direction cardinalities

0 .. *

attribute attribute type

name edge

attributes

Graph Schema - Notation

UML object diagram (hierarchical graph)

u : U t : T

f : F

v : V e : E w : W

g : G

UML class diagram (schema)

V E W

T

U

F

Composition G

Graph Schema - Higher Constructs

Generalization

Aggregation

Exchanging Schemas

GXL First Directive

Everything is a typed, attributed, directed graph

Conclusion

– Schemas (UML class diagrams) are represented as graphs as well

– Schemas are exchanged as GXL documents suiting a metaschema for schema graphs – only one common and simple DTD for

exchanging

• graphs matching different graph schemas and

• graph schemas matching a metaschema

GXL Schema Representation

UML class diagram

Var file:string

line : int line : int

Proc

refers

:

Nodetyp e

name="Proc"

:

Attribut e

name="file"

:

Domain

name="string"

:

Edgetype name="refers"

:

Nodetype name="Var"

:

Domain name="int"

:

Attribut e

name="line"

from

to

hasAttr hasDom

hasAttr

hasAttr

hasDom

approach

schema graph

?

Conclusion

GXL offers a standard exchange language for

– graphs

– graph schemas

GXL uses one common DTD for exchanging

– graphs

– graph schemas

more information

– http://www.gupro.de/GXL

next Steps

• define the concrete subset of UML class diagrams, necessary for exchanging

graph schemas

• define the GXL metaschema for exchanging schema graphs (after dinner)

• define reference schemas for various applications

– different languages

– different levels of granularity Please send us your schemas

Upcoming Events

• Dagstuhl Seminar "Interoperability of Reengineering Tools" (January 21-26, 2001)

(ask Kostas, if you want to participate)

• APPLIGRAPH Meeting "Exchange Formats for Graph Transformation" (Spring,

Bremen)

• WoSEF 2001