Web Data Models. XPath: Syntax, Semantics Silviu Maniu

Transcription

1 We Dt Moels XPth: Syntx, Semntis Silviu Mniu

2 XPth one we hve n XML oument, we wnt to query it n retrieve t XPth: query lnguge to selet sequene of noes from n XML W3C stnr lso use in other stnrs (XQuery, XSLT, XPointer, XLink, ); supporte y every moern rowser

3 XPth XPth is nvigtionl lnguge speifies how the XML ouments shoul e trverse Min issue: ig volume of noes n e extrte vi XPth, so effiient proessing is still n ongoing hllenge

4 Leture Outline XPth xes XPth tests XPth noes

5 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

6 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

7 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

8 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

9 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> R1 = <title>fountions of Dtses</title> R2 = <title>priniples of Dtse n Knowlege Bse Systems</title> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

10 XPth XPth is ompose of sequene of ontext noes n step: s 0 /step fter the ontext sequene, tke step in given iretion n lso hve multi-steps: s 0 /step 1 /step 2 /... s 1 /step 2 /...

11 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

12 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

13 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

14 XPth: Quik Exmple <i> Q1 = /i/ook/title <ook> <uthor>aiteoul</uthor> <uthor>hull</uthor> <uthor>vinu</uthor> <title>fountions of Dtses</title> <yer>1995</yer> </ook> <ook> <uthor>ullmnn</uthor> <title>priniples of Dtse n Knowlege Bse Systems</title> <yer>1998</yer> </ook> </i>

15 XPth: Syntx Eh step hs the syntx: xis :: ntest[pre 1 ] [pre n ] xis speifies the iretion of nvigtion to e followe, ntest speifies the noe test (use to nvigte only noes of ertin kin), the optionl pre, whih llows filters on the sequene of noes we nvigte to.

16 XPth: Axes xis :: ntest[pre 1 ] [pre n ] XPth hs fmily of 12 xes llowing for flexile nvigtion within the noe hierrhy forwr xes (in oument orer) kwr xes (in reverse oument orer)

17 <> XPth: Axes < /> <> < /> < x= 1.0 > <>text1</> <> < /> < /> </> </> <> < /> <>text2</> x </> </> < /> </>

18 XPth: Axes self (fw) hil (fw) prent (k) x ttriute (fw)

19 XPth: Axes self (fw) esennt (fw) nestor (k) x

20 XPth: Axes preeing (k) following (fw) nestor-or-self (k) x

21 XPth: Axes preeing-siling (k) following-siling (fw) esennt-or- x self (fw)

22 XPth: Result Orer The result noe sequene of ny XPth nvigtion is returne in oument orer with no uplite noes.

23 XPth: Noe Tests Cn lso pply noe test to filter noes se on kin n nme. xis :: ntest[pre 1 ] [pre n ] Test noe() text() omment() proessing-instrution() proessing-instrution(p) oument-noe() Semntis let ny noe pss preserve only text noes preserve only omment noes preserve proessing instrutions preserve proessing instrutions of the form <?p p> preserve the oument root noe

24 XPth: Noe Tests Cn lso pply noe test to filter noes se on kin n nme. xis :: ntest[pre 1 ] [pre n ] Test nme * Semntis preserve element noe with tg nme only preserve element noes with ritrry tg nmes

25 XPth: Arevitions There re few revitions in XPth: / /hil:: // /esent-or-self::noe()/hil:: // /esennt-or-self::noe(). /self::noe().. ttriute::

26 XPth: Exmples Q1 := /// x

27 XPth: Exmples Q1 := /// x

28 XPth: Exmples Q2 := //// x

29 XPth: Exmples Q2 := //// x

30 XPth: Exmples Q3 := ///hil::noe()// x

31 XPth: Exmples Q3 := ///hil::noe()// x

32 XPth: Exmples Q4 := ///// x

33 XPth: Exmples Q4 := ///// x

34 XPth: Preites Preites re teste ginst noe, n re optionl. xis :: ntest[pre 1 ] [pre n ] they hve higher preeene thn the XPth step, re evlute left to right, they my e ny XQuery expression whih evlutes to vlue v

35 XPth: Preites xis :: ntest[pre 1 ] [pre n ] XPth lultes n effetive oolen vlue ev(v), epening on the vlue v: v ev(v) () flse() 0, NN flse() " flse() flse() x (x1,x2,,xn) flse() true() true()

36 XPth: Exmples Q5 := ///[./] x

37 XPth: Exmples Q5 := ///[./] x

38 XPth: Exmples Q6 := ///[ n ] x

39 XPth: Exmples Q6 := ///[ n ] x

40 XPth: Exmples Q7 := ///[not()] x

41 XPth: Exmples Q7 := ///[not()] x

42 XPth: Preites xis :: ntest[pre 1 ] [pre n ] Preites llow testing for ttriute vlues.

43 XPth: Exmples Q8 := x 1.0"

44 XPth: Exmples Q9 := 1.0 ] x 1.0"

45 XPth: Exmples Q9 := 1.0 ] x 1.0"

46 XPth: Preites xis :: ntest[pre 1 ] [pre n ] Preites llow testing for text in noes.

47 XPth: Exmples Q10 := /////*[text()= text1 ] x text1" text2

48 XPth: Exmples Q10 := /////*[text()= text1 ] x text1" text2

49 XPth: Useful Preite Funtions xis :: ntest[pre 1 ] [pre n ] Preites llow funtions for testing on noe sets: Funtion ount(ex) lst() position() Semntis ounts numer of results returns ontext size from the evlution ontext returns ontext position from the evlution ontext

50 XPth: Useful Preite Funtions xis :: ntest[pre 1 ] [pre n ] Preites llow funtions for testing on strings: Funtion ont(s1,,sn) strtswith(str,pre) ontins(str,sustr) sustring(str,i,j) stringlength(str) Return vlue ontente string true() if str strts with pre true() if str ontins sustr the sustring of str from i to j the length of str

51 Useful Reing XPth Referene Mrh Shol s slies on XPth P8.pf Sestin Mneth s slies on XPth pf