Miguel Romero

1

A Graph-Oriented Model and Query Language for
Events

• Miguel Romero
• University of Bío-Bío, Chile
• mromero_at_pehuen.chillan.ubiobio.cl

Andrea Rodríguez University of Concepción,
Chile andrea_at_udec.cl
2
Contents

• Introduction
• Events Model
• Query Language
• Prototype
• Conclusions and future work

3
Introduction

• Events are present in diverse areas as
  simulation, active database, business process and
  so on
• Two complementary views of events in information
  systems are.
• events are triggering conditions rather than
  being stored and queried as traditional data,
  such as events in active databases and in
  reactive Web applications and services.
• events are subject of data representation and
  query processing, such as events in
  spatio-temporal databases.

4
Introduction

• We consider events in the context of
  spatio-temporal databases, where events establish
  something that happens at a specific location and
  time instant or interval.
• Considering events as subject of representation
  leads us to model events as entities in a
  database system.
• Unlike entities in traditional databases systems,
  relationships between events, play an important
  role for querying events, like temporal order,
  spatial connectivity or causality.

5
1960 Chilean Earthquake
6
Introduction

• The main contribution of the work is to address
  modelling, representation, and query
  specification of events from a different
  perspective, where the focus is to query about
  events rather than about the changes in objects
  states.

7
Events Model

• In this work, we extend models and query
  languages for graphs to represent events as
  follows
• Events are represented as nodes in a graph, with
  their particular properties (temporal and spatial
  settings).
• Edges in a graph represent causality
  relationships between events.
• Both events and causality relationships can be
  modelled at different levels of granularity.

8
Different levels of granularity
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Events Model
EVENT ? EDGE ? EVENT_GRAPH event_graph
LABEL ? (ATOMIC_EVENT ? COMPOSITE_EVENT) ? EVENT
event
ATOMIC_EVENT ? EVENT_GRAPH ? COMPOSITE_EVENT
composite_event
INTERVAL ? SPATIAL ? ATOMIC_EVENT atomic_event
LABEL ? (ATOMIC_EDGE ? COMPOSITE_EDGE) ? EDGE
edge
COMPOSITE_EVENT ? COMPOSITE_EVENT ? EDGE ?
COMPOSITE_EDGE composite_edge
EVENT ? EVENT ? ATOMIC_EDGE atomic_edge
INSTANT ? INSTANT ? INTERVAL interval
string ? BASE ? LABEL label
string ? INSTANT instant
Set type List type
? SPATIAL point, line, polygon, region
? BASE int, real, string, bool
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Main Operators

• Event_graph
• events, edges returns a set of events or edges
• get_event, get_edge returns a particular event
  or edge.
• project_each_event, project_each_edge
  projection of labels.
• select_each_event, select_each_edge filter the
  graph with a function selection.
• union, intersection, difference of graph

11
Main Operators (cont.)

• Event
• is_atomic is true for atomic event
• get_graph, get_interval, get_spatial return a
  graph, interval and spatial setting.
• str_Label_Value, int_Label_Value,
  real_Label_Value return a labels value.
• Edge
• is_atomic is true for atomic edge
• edges, source, target return a set of edges,
  source event and target event
• str_Label_Value, int_Label_Value,
  real_Label_Value return a labels value.

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Main Operators (cont)

• Interval
• start, end time point of interval
• classic Allen Operator equals , diferent,
  before, after, meets, metby, finishes,
  finishedby, overlaps, overlappedby, starts,
  startedby, during, contains

13
Query Language

• All events and their relationships ocurred before
  of 1961/01/01 in Chile and Argentina.
• query
• earthquakeChileDB do
• select_each_event(fun(ev event)
• get_interval(ev) before new_interval(1961))
  
• Done
• union
• earthquakeArgentinaDB do
• select_each_event(fun(ev event)
• get_interval(ev) before new_interval(1961))
  
• Done

1961
earthquakeChileDB
6
earthquakeArgentinaDB
7
8
Result of query
1
5
3
2
4
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Query Language

• All earthquakes of strength gt 7.5 that caused a
  tsunami.
• query earthquakeDB do
• select_each_edge(fun(eedge) earthquakeDB
  get_event(target(e))
• str_label_value(Type)tsunami
  select_each_event(fun(xevent)
• (x str_label_value(Type))earthquake and (x
  real_label_value(strength") gt 7.5
• done

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Lenguaje en BNF

• ltquerygt query ltgraph formulagtltevent
  formulagtltedge formulagt
• ltgraph formulagt ltgraph querygtltgraph
  expressiongtltgraph objectgt
• ltgraph querygt
• ltgraph formulagt do
• project_each_event(ltlabel namegt, ltlabel
  namegt)
• project_each_edge(ltlabel namegt, ltlabel
  namegt)
• select_each_event(fun(ltvar
  namegtevent)ltboolean formulagt)
• select_each_edge(fun(ltvar namegtedge)ltboolean
  formulagt)
• done
• ltgraph expressiongt ltgraph formulagt union
  ltgraph formulagt
• ltgraph formulagt intersection ltgraph
  formulagt
• ltgraph formulagt difference ltgraph formulagt
  get_event_graph(ltevent formulagt)
• ltpath formulagt ltpath objectgt paths(ltgraph
  formulagt)
• ltevent formulagt ltevent objectgt ltevent out
  operatorgt
• ltedge formulagt ltedge objectgt ltedge out
  operatorgt
• ltboolean formulagt ltboolean objectgt
  not(ltboolean formulagt)
• ltboolean formulagt and ltboolean formulagt
• ltboolean formulagt or ltboolean formulagt
• lt relational formulagt lt allen formulagt

16
Implementation

• SECONDO, an extensible Database Systems
• Generic database system framework,
• extended by algebra module, viewer object and
  optimizer rueles.
• we extended SECONDO by
• New algebra module Event Algebra (EA).
• New viewer objects Event viewer (EV).

EV
EA
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Secondo GUI
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Conclusion and future works

• we proposed a graph-based approach to modeling
  events and their interrelations.
• We discussed the need of making explicit the
  relationships between events, and we have
  extended current graph data models to include
  temporal and spatial settings and to manage
  different levels of granularity for representing
  events and their relationships.
• As future work, we would like to fully implement
  the model in the extensible database system, by
  including path queries and interoperation with
  existing spatial algebras. The event query
  language can be extended and adapted to standard
  query languages.
• There are also research issues concerning
  temporal granularity that could be further
  addressed, as well as reasoning with unknown
  temporal or spatial settings.
• We also evaluate to use another graph oriented
  language (e.g. XQuery) to implement this model.

19

A Graph-Oriented Model and Query Language for
Events Thanks!

• Miguel Romero
• University of Bío-Bío, Chile
• mromero_at_pehuen.chillan.ubiobio.cl

Andrea Rodríguez University of Concepción,
Chile andrea_at_udec.cl