Databases and Information Systems 2

Transcription

Databases and Information Systems 2
Prof. Dr. Stefan Böttcher
Fakultät EIM, Institut für Informatik
Universität Paderborn
SS 2007
Contents:
• Why mobile XML database systems ?
• New database technology for
mobile XML database systems (and other DBS)
• Further topics (e.g. web technology, middleware, EJB, …)
Databases and Information Systems 2 - SS 20 07 - Prof. Dr. Stefan Böttcher
-
Introduction / 1
Why XML ?
<20 % of data stored in relational DBs
>80 % of data stored in documents
- more or less structured
semi-structured
Structure supports retrieval of data and knowledge
XML used as standard data exchange protocol for
middleware (SOAP), web services, …
product catalogs (BMEcat), …
-
Introduction / 2
1
XML in relational databases?
Assume you have a relational database system.
How would you use it in XML-based applications,
i.e. applications that want to
exchange, read, transform, … XML data?
exercise
XML 
-
Introduction / 3
database mappings
• mapping XML + XPath to relational databases + datalog
• mapping databases to XML (
• flat database
DBIS 2 )
XML mapping
• hierarchical database
XML mapping
• limitations of reverse mappings
-
Introduction / 4
2
Implementing XML by relational databases
• many different approaches
one based on label, first-child (fc) and next-sibling(ns)
<Auftrag>
<Kunde>Meier</Kunde>
<PC>pc500</PC>
</Auftrag>
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
Introduction / 5
-
Implementing XML by relational databases
• many different approaches
one based on label, first-child (fc) and next-sibling(ns)
<Auftrag>
<Kunde>Meier</Kunde>
<PC>pc500</PC>
</Auftrag>
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
label( ID, Label) fc(P,FC)
ID Label(ID)
ID fc(ID)
1
root
1
2
2
Auftrag
2
3
3
Kunde
3
4
4
Meier
5
6
5
PC
6
pc500
ns(ID,NS)
ID
ns(ID)
3
5
-
Introduction / 6
3
Implementing XML axes by Datalog programs
following-sibling(X,Y) = ns+(X,Y) ; // implementation in datalog as usual
following-sibling(X,Y) :- ns( X, Y ).
following-sibling(X,Y) :- ns( X, NS ), following-sibling(NS,Y) .
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
child(X,Y) :- fc(X,Y) .
child(X,Y) :- fc(X,FC) ,
following-sibling( FC, Y ).
ID Label(ID)
ID fc(ID)
1
root
1
2
2
Auftrag
2
3
3
Kunde
3
4
4
Meier
5
6
5
PC
6
pc500
ns(ID,NS)
ID
ns(ID)
3
5
-
Introduction / 7
// following-sibling(X,Y) = ns+(X,Y) . // implementation in datalog as usual
following-sibling(X,Y) :- ns( X, Y ).
following-sibling(X,Y) :- ns( X, NS ), following-sibling(NS,Y) .
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
child(X,Y) :- fc(X,Y) .
child(X,Y) :- fc(X,FC) ,
following-sibling( FC, Y ).
// descendant( X, Y ) = child+(X,Y) .
descendant(X,Y) :- child( X, Y ).
descendant(X,Y) :- child( X, C ) ,
descendant(C,Y) .
-
Introduction / 8
4
reverse-axis(X,Y) = reverse-axis-1(Y,X)
ancestor( D, A ) :- descendant( A, D ) .
parent( C, P ) :- child ( P, C ) .
parent( A, P ) :- attribute ( P, A ) .
parent( N, P ) :- namespace ( P, N ) .
Axis-or-self(X,Y) = Axis(X,Y)
Axis-or-self(X,Y) = self(X,Y)
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
self( X, X ).
descendant-or-self( A, D ) :- descendant( A, D ).
descendant-or-self( A, D ) :- self( A, D ).
ancestor-or-self( D, A ) :- ancestor( D, A ).
ancestor-or-self( D, A ) :- self( D, A ).
-
Introduction / 9
following::* = ancestor-or-self::* / following-sibling::* / descendant-or-self::*
following(X,Y) :- ancestor-or-self(X,A) ,
following-sibling(A,S) ,
descendant-or-self(S,Y) .
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
preceding(X,Y) :- following(Y,X) .
-
Introduction / 10
5
Implementing XPath queries by Datalog queries
// Kunde
?- goal(K).
goal(K) :- label( R, “root“ ) ,
descendant( R , K ) ,
label( K , “Kunde“ ) .
Answer:
K=3.
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
(R=1)
-
Introduction / 11
Implementing XPath queries by Datalog queries
// Kunde
?- goal(K).
descendant( R , K ) ,
label( K , “Kunde“ ) .
Answer:
K=3.
1
root
2
Auftrag
3
Kunde
5
PC
4
Meier
6
pc500
(R=1)
// Auftrag [ PC ] / Kunde
?- goal2( K ).
descendant( R, A ) ,
child( A, P ) ,
label( P , "PC" ) ,
child( A, K ) ,
label( K , "kunde" ) .
(R=1)
(A=2)
(P=5)
(K=3)
-
Introduction / 12
6
Evaluation of XPath implemented by Datalog
use fast algorithm for Datalog evaluation, e.g. Process Model,
that combines Top-Down selection-first evaluation
with set-oriented bottom-up computation
only unary and binary base relations
subclass of Datalog programs that can be evaluated efficiently
-
Introduction / 13
Limits of implementing XML/XPath by Datalog
• updates of XML documents
updates of datalog views (o.K.)
however:
beyond this point:
view update problem
-
Introduction / 14
7
Summary: XML/XPath implemented by Datalog
• base relations:
Label( ID, Label ) , fc( Parent, FirstChild ) , ns( Node, NextSibling )
• recursive deductive database rule systems for
following-sibling( Node , FS )
child( Parent, Child ) ,
descendant( Node, Descendant )
•
combination rules for
following( Node, Following )
descendant-or-self( Node , DOS )
ancestor-or-self( Node , AOS )
• reverse-axis Datalog rules for
ancestor( Node, Ancestor )
parent( Node, Parent )
preceding-sibling( Node, PrecedingSibling )
preceding( Node, Preceding )
-
Introduction / 15
Commercial XML database systems (1)
XML as an extension to an existing relational database
- data is already stored in a relational database (e.g. Oracle)
- extra data type generates XML
doc
name =
“Meier“
order
customer
customer
address
order
address
Customer
name
order address
-
Introduction / 16
8
extra columns of type XML document (e.g. Microsoft)
+ original XML documents can be stored
+ search in stored XML documents
+ XPath queries are transformed into internal queries
date
orders
XML document containing orders of date
doc
name =
“Meier“
order
…
customer
customer
address
order
…
address
…
-
Introduction / 17
hybrid XML database system (e.g. IBM DB2 Universal Server):
- relational data stored in relational database
- XML data stored in separate storage
+ both parts of the database accessable via join queries
+ effizient access in the relational part of the database
+ external XML documents can be stored
+ search in stored XML documents
-
Introduction / 18
9
Why mobile XML database systems?
increasing market share of mobile devices (cellulars, PDAs, …)
using data intensive applications in mobile environments
requires involving database technology for mobile devices
current middleware data exchange format is XML
XML data exchange required
payment, contracts, … via or between mobile devices
demands data persistence and
atomic contracts involving or between mobile devices
-
Introduction / 19
Challenges of mobile XML databases
Assume you want to port XML-based data intensive applications
to mobile devices.
What are the typical database system challenges
(in contrast to, i.e. omitting challenges to network technology) ?
Exercise:
1. describe goals
"a mobile database system should … <Goal X> "
2. for each goal think of and discuss the technical requirements
"in order to achieve X, the database system should achieve/guarantee Y "
3. for each goal think of and discuss possible solution ideas
"in order to meet requirement Y, the database system could do … "
-
Introduction / 20
10

Databases and Information Systems 2

Transcription

Documents pareils

practical memo - Cabane du perche

the new concept - Dj

CREDIT APPLICATION

Montpellier FR-GB 2016-v1

Practical Information

Calais FR-GB 2016-v1

Lectures free to all members of the University

Application Form - The French American Academy