[PDF] - Plan 1. Information in tegration: imp ortan t new PDF Document

SLIDE 1 Plan 1. Information in tegration: imp

rtan

t new application that motiv ates what follo ws. 2. Semistructured data: a new data mo del designed to cop e with problems

f

information in tegration. 3. XML: a new W eb standard that is essen tiall y semistructured data. 4. X QUER Y: an emerging standard query language for XML data. 1

SLIDE 2 Information In tegration Problem: related data exists in man y places. They talk ab

ut

the same things, but dier in mo del, sc hema, con v en tions (e.g., terminology). Example In the real w

rld,

ev ery bar has its

wn

database.

Some

ma y ha v e relations lik e b eer-price;

thers

ha v e an MS-w

rd

le from whic h the men u is prin ted.

Some

k eep phones

f

man ufacturers but not addresses.

Some

distinguish b eers and ales;

thers

do not. 2

SLIDE 3 Tw

approac

hes 1. War ehousing : Mak e copies

f

information at eac h data source cen trally .

✦

Reconstruct data daily/w eekl y/mon thly , but do not try to k eep it up-to-date. 2. Me diation : Create a view

f

all information, but do not mak e copies.

✦

Answ er queries b y sending appropriate queries to sources. 3

SLIDE 4 W arehousing W rapp er W rapp er Com biner DB1 DB2 W arehouse user query result 4

SLIDE 5 Mediation W rapp er W rapp er DB1 DB2 Mediator query result query result result query query result query result 5

SLIDE 6 Semistructured Data

A

dieren t kind

f

data mo del, more suited to information-in tegration applications than either relational

r

OO.

✦

Think

f

\ob jects," but with the t yp e

f

an

b

ject its

wn

business rather than the business

f

the class to whic h it b elongs.

✦

Allo ws information from sev eral sources, with related but dieren t prop erties, to b e t together in

ne

whole.

Ma

jor application: XML do cumen ts. 6

SLIDE 7 Graph Represen tati

n
f

Semistructured Data

No

des =

b

jects.

No

des connected in a general ro

ted

graph structure.

Lab

els

n

arcs.

A

tomic v alues

n

leaf no des.

Big

deal: no restriction

n

lab els (roughly = attributes).

✦

Zero,

ne,
r

man y c hildren

f

a giv en lab el t yp e are all OK. 7

SLIDE 8 Example M'lob 1995 Gold Bud A.B. prize a w ard y ear name manf manf b eer b eer bar Jo e's Maple name addr serv edA t name 8

SLIDE 9 XML (Extensible Markup Language) HTML uses tags for formatting (e.g., \itali c") . XML uses tags for seman tics (e.g., \this is an address").

Tw
mo

des: 1. Wel l-forme d XML allo ws y

u

to in v en t y

ur
wn

tags, m uc h lik e lab els in semistructured data. 2. V alid XML in v

lv

es a DTD (Do cumen t T yp e Denition) that tells the lab els and giv es a grammar for ho w they ma y b e nested. 9

SLIDE 10 W ell-F

rmed

XML 1. Declaration = <? ... ?>.

✦

Normal declaration is <? XML VERSION = "1.0" STANDALONE = "yes" ?>

✦

\Standalone" means that there is no DTD sp ecied. 2. R

t

tag surrounds the en tire balance

f

the do cumen t.

✦

<FOO> is balanced b y </FOO>, as in HTML. 3. An y balanced structure

f

tags OK.

✦

Option

f

tags that don't r e quir e balance, lik e <P> in HTML. 10

SLIDE 11 Example <?XML VERSION = "1.0" STANDALONE = "yes"?> <BARS> <BAR><NAME>Joe's Bar</NAME> <BEER><NAME>Bud< /NAME > <PRICE>2.50</PRICE>< /BEER > <BEER><NAME>Mill er</N AME> <PRICE>3.00</PRICE>< /BEER > </BAR> <BAR> ... </BARS> 11

SLIDE 12 Do cumen t T yp e Denitions (DTD) Essen tially a grammar describing the legal nesting

f

tags.

In

ten tion is that DTD's will b e standards for a domain, used b y ev ery

ne

preparing

r

using data in that domain.

✦

Example: a DTD for describing protein structure; a DTD for describing bar men us, etc. Gross Structure

f

a DTD <!DOCTYPE r

ot

tag [ <!ELEMENT name (components)> mor e el ements ]> 12

SLIDE 13 Elemen ts

f

a DTD An element is a name (its tag) and a paren thesized description

f

tags within an elemen t.

✦

Sp ecial case: (#PCDATA) after an elemen t name means it is text. Example <!DOCTYPE Bars [ <!ELEMENT BARS (BAR*)> <!ELEMENT BAR (NAME, BEER+)> <!ELEMENT NAME (#PCDATA)> <!ELEMENT BEER (NAME, PRICE)> <!ELEMENT PRICE (#PCDATA)> ]> 13

SLIDE 14 Comp

nen

ts

Eac

h elemen t name is a tag.

Its

comp

nen

ts are the tags that app ear nested within, in the

rder

sp ecied.

Multipli

ci t y

f

a tag is con trolled b y: a) * = zero

r

more

f.

b) + =

ne
r

more

f.

c) ? = zero

r
ne
f.
In

addition, | = \or." 14

SLIDE 15 Using a DTD 1. Set STANDALONE = "no". 2. Either a) Include the DTD as a pream ble,

r

b) F

llo

w the XML tag b y a DOCTYPE declaration with the ro

t

tag, the k eyw

rd

SYSTEM, and a le where the DTD can b e found. 15

SLIDE 16 Example

f

(a) <?XML VERSION = "1.0" STANDALONE = "no"?> <!DOCTYPE Bars [ <!ELEMENT BARS (BAR*)> <!ELEMENT BAR (NAME, BEER+)> <!ELEMENT NAME (#PCDATA)> <!ELEMENT BEER (NAME, PRICE)> <!ELEMENT PRICE (#PCDATA)> ]> <BARS> <BAR><NAME>Joe's Bar</NAME> <BEER><NAME>Bud< /NAME > <PRICE>2.50</PRICE>< /BEER > <BEER><NAME>Mill er</N AME> <PRICE>3.00</PRICE>< /BEER > </BAR> <BAR> ... </BARS> 16

SLIDE 17 Example

f

(b) Supp

se
ur

bars DTD is in le bar.dtd . <?XML VERSION = "1.0" STANDALONE = "no"?> <!DOCTYPE Bars SYSTEM "bar.dtd"> <BARS> <BAR><NAME>Joe's Bar</NAME> <BEER><NAME>Bud< /NAME > <PRICE>2.50</PRICE>< /BEER > <BEER><NAME>Mill er</N AME> <PRICE>3.00</PRICE>< /BEER > </BAR> <BAR> ... </BARS> 17

SLIDE 18 A ttribute Lists Op ening tags can ha v e \argumen ts" that app ear within the tag, in analogy to constructs lik e <A HREF = ...> in HTML.

Keyw
rd

!ATTLIST in tro duces a list

f

attributes and their data t yp es. Example <!ELEMENT BAR (NAME BEER*)> <!ATTLIST BAR type = "sushi"|"sports"|"o ther" >

Bar
b

jects can ha v e a (bar) t yp e, and the v alue

f

that t yp e is limited to the three strings sho wn.

Example
f

use: <BAR type = "sushi"> . . . </BAR> 18

SLIDE 19 ID's and IDREF's These are p

in

ters from

ne
b

ject to another, analogous to NAME = "foo" and HREF = "#foo" in HTML.

Allo

ws the structure

f

an XML do cumen t to b e a general graph, rather than just a tree.

An

attribute

f

t yp e ID can b e used to giv e the

b

ject (string b et w een

p

ening and closing tags) a unique string iden tier.

An

attribute

f

t yp e IDREF refers to some

b

ject b y its iden tier.

✦

Also IDREFS to allo w m ultiple

b

ject references within

ne

tag. 19

SLIDE 20 Example Let us include in

ur

Bars do cumen t t yp e elemen ts that are the man ufacturers

f

b eers, and ha v e eac h b eer

b

ject link, with an IDREF, to the prop er man ufacturer

b

ject. <!DOCTYPE Bars [ <!ELEMENT BARS (BAR*, MANF*)> <!ELEMENT BAR (NAME, BEER+)> <!ELEMENT NAME (#PCDATA)> <!ELEMENT MANF (ADDR)> <!ATTLIST MANF (name ID)> <!ELEMENT ADDR (#PCDATA)> <!ELEMENT BEER (NAME, PRICE)> <!ATTLIST BEER (manf = IDREF)> <!ELEMENT PRICE (#PCDATA)> ]> 20

SLIDE 21 X QUER Y Emerging standard for querying XML do cumen ts. Basic form: FOR <variables ranging

ver

sets

f

elements> WHERE <condition> RETURN <set

f

elements>;

Sets
f

elemen ts describ ed b y p aths, consisting

f:

1. URL, if necessary . 2. Elemen t names forming a path in the semistructured data graph, e.g., //BAR/NAME = \start at an y BAR no de and go to a NAME c hild." 3. Ending condition

f

the form [<condition about subelements, attributes (preceded by @), and values>]. 21

SLIDE 22 Example The le http://www.stanford. edu/b ars.x ml: <?XML VERSION = "1.0" STANDALONE = "no"?> <!DOCTYPE Bars SYSTEM "bar.dtd"> <BARS> <BAR type = "sports"> <NAME>Joe's Bar</NAME> <BEER><NAME>Bud< /NAME > <PRICE>2.50</PRICE>< /BEER > <BEER><NAME>Mill er</N AME> <PRICE>3.00</PRICE>< /BEER > </BAR> <BAR type = "sushi"> <NAME>Homma's</N AME> <BEER><NAME>Sapp

ro</

NAME> <PRICE>4.00</PRICE>< /BEER > </BAR> ... </BARS> 22

SLIDE 23 X QUER Y Query Find the prices c harged for Bud b y sp

rts

bars that serv e Miller. FOR $ba IN document("http://w ww.st an- ford.edu/bars.ht ml") //BAR[@type = "sports"], $be IN $ba/BEER[NAME = "Bud"] WHERE $ba/BEER/[NAME = "Miller"] RETURN $be/PRICE; 23