digraph prehistory {
rankdir=LR;
ranksep=2.0;
subgraph orgs {
UOC [ rank=3 URL="https://www.uoc.edu/portal/ca/index.html" tooltip="Universitat Oberta de Catalunya"]
BITPlan [  URL="http://www.bitplan.com" tooltip="BITPlan" ]
TUM [  URL="https://wwwmatthes.in.tum.de/pages/t5ma0jrv6q7k/sebis-Public-Website-Home"  tooltip="TUM"  ]
}

subgraph people {
Jordi_Carbot [ rank=2 label="Jordi Carbot"  URL="https://twitter.com/softmodeling" ] 
Wolfgang_Fahl [ label="Wolfgang Fahl" URL="https://twitter.com/seppl2009"]
Florian_Matthes [ label="Florian Matthes" URL="https://twitter.com/matthes" ]
Robert_Clariso [ label="Robert Clarisó" URL="https://www.uoc.edu/webs/rclariso/EN/curriculum/index.html" ]
Christof_Tinnes [ label="Christof Tinnes" URL="https://wwwmatthes.in.tum.de/pages/v2o7t4t0vg87/Christof-Tinnes" ]
}

subgraph messages {
Article [ rank=1 URL="https://modeling-languages.com/graph-kernels-model-driven-software-engineering/" ]
Tweet [ URL="https://twitter.com/softmodeling/status/1033777854239199232" ]
ReTweet [ URL="https://twitter.com/seppl2009/status/1033787770819497985" ]
Offer [ URL="http://wiki.bitplan.com/index.php/Graph_Approaches_for_Software_Engineeering" ]
Invitation [ URL="https://wwwmatthes.in.tum.de/pages/rwzby1tlqhn9/Advanced-Seminar"]
}

subgraph topics {
SimpleGraph [ rank=4 URL="http://www.bitplan.com/index.php/SimpleGraph" ]
}

Robert_Clariso -> Article [ label="1 publishes" ]
Robert_Clariso -> UOC [ label="from" ]

Jordi_Carbot-> Tweet [ label="2 tweets"]
Tweet->Article [ label="links to" ]
Jordi_Carbot -> UOC [ label="from" ]

Wolfgang_Fahl -> ReTweet [ label="3 retweets" ]
ReTweet -> Tweet [ label="retweet of" ] 
Wolfgang_Fahl -> BITPlan [ label="from" ]

Florian_Matthes -> ReTweet [ label="4 likes" ]
Florian_Matthes -> TUM [ label="from" ]
Wolfgang_Fahl -> Offer [ label="5 offers" ]
Offer -> SimpleGraph [ label="to present" ]

Florian_Matthes -> Offer [ label="6 accepts" ]
Christof_Tinnes -> Invitation [ label="7 invites" ]
Wolfgang_Fahl -> Invitation [ label="8 accepts" ]

edge[dir=none];


{rank=same; Article-> Tweet -> ReTweet -> Offer -> Invitation;}
{rank=same; Robert_Clariso -> Jordi_Carbot -> Wolfgang_Fahl -> Florian_Matthes -> Christof_Tinnes;}
{rank=same; UOC -> BITPlan ->TUM ;}


}