Overview of Prometheus Mediator. Snehal Thakkar CSCI 548 Information Integration On the Web

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1 Overview of Prometheus Mediator Snehal Thakkar CSCI 548 Information Integration On the Web

2 Outline Prometheus mediator Brief Introduction Understanding data sources Installation Global-As-View Local-As-View Using from another Java program Frequently asked questions

3 Introduction Mediator system that supports Global-As-View Local-As-View Using Inverse Rules Plan optimization using heuristics Efficient execution using Theseus Inputs A domain file A query file Optional source file

4 Understanding Data Sources Sources can be Databases, wrappers, web services, Theseus plans Have A schema Attribute names, types, binding restrictions Access method url for the wrapper, pointer to the database

5 Installation Download a zip file from the URL given in the homework Unzip the file in one directory To run any example Go to the examples\databases (or other example) directory Type runlocal.bat test1q.txt -o Press enter

6 Mediator Parameters Look through the runlocal.bat We pass d domainfile(hardcoded as test.txt in the batch file, but u can change it if you like) -q queryfile Optional s sourcefile (needed for LAV) Optional o (optimize the generated plans) You will almost always want to run it with o Optional debug Use it to see debugging info such as the theseus plan Optional g Use it to get dotty representation of the graph

7 Global-As-View Using Prometheus to do GAV integration Create wrappers (or databases, or theseus plans) for your sources Specify a file containing domain description Specify a query file Run the mediator!!

8 Domain File Three sections SourceSchemas Information about attributes of the sources Example: source1(attr1:attr1type:b, attr2:attrtype2:f ) SourceTypes Information about sources (wrappers, databases, etc) Example: source1(wrapper, src1, ) Rules Datalog rules Relationships between domain concepts and sources Domainrel1(x, y, z) :- source1(x,y)^source2(y, z)

9 Query File Only one section Queries : Datalog predicates Conjunctions and disjunctions are allowed Multiple queries in file are allowed Example Q1(x, y, z) :- domainrel1(x, y) ^ domainrel2(y, z) ^ (z = 15 )

10 Examples Table Name Database Attribute Names SourceSchemas: s1(emp:string:f, dept:string:f, sal:string:f) SourceTypes: s1(database, test, "jdbc:odbc:driver={microsoft Access Driver (*.mdb)};dbq=test.mdb!u!p") Rules: Database Name employee(name, dept, sal) :- s1(name, dept, sal) Domain Predicate

11 Examples (Cont d) Query q1(n, d, s) :- employee(n, d, s) Output <result> <q1> <row> <n type="string">pat</n> <d type="string">sales</d> <s type="string">30</s> </row>... </q1>

12 Example of using a wrapper SourceSchemas: wrapper1(address:string:b, Parcel:string:f, Owner:string:f, Addr:string:f, Desc:string:f)

13 Example of using a wrapper SourceSchemas: wrapper1(address:string:b, Parcel:string:f, Owner:string:f, Addr:string:f, Desc:string:f) SourceTypes: wrapper1(wrapper, Summit, " pper1%2fplans%2fproduction") Rules:.

14 Example GAV Application Let s see the Prometheus mediator in action In the GAV mode To run the example go the examples\databases directory and type runlocal.bat test1q.txt o You should see whole bunch of xml Repeat the same in the wrapper directory

15 Local-As-View No Different then using GAV except You have to write the source descriptions Pass the sourcefile Remember from earlier part Write sources as views over domain relations s1(x, y, z, cr) :- seaports(x, y, z, cr)^(cr < 7 )

16 Example Domain file Database SourceSchemas: s1(emp:string:f, dept:string:f, sal:string:f) SourceTypes: s1(database, test, "jdbc:odbc:driver={microsoft Access Driver (*.mdb)};dbq=test.mdb!u!p") Rules:

17 Example Source file s1(name, dept, sal) :- Source Name employee(name, dept, sal) Domain Predicate

18 Calling Mediator from Java Its actually pretty simple Hardest part is to make sure that you have Theseus and mediator jar files in your class path to compile and run your java class Edit runlocal.bat For GAV String domainfile = "webl_empl.txt"; String querystr = "q1(person, args, number) :- person(person, args, number)^(person=\"abc\") "; String xmlresults = Mediator.doQuery(domainFile, querystr); System.out.println(xmlresults);

19 Calling Mediator from Java For LAV String domainfile = "webl_empl.txt"; String domainstr = {read the domain file into string}; String srcfile = "webl_empl_src.txt"; String srcstr = {read the source file into string}; String querystr = "q1(person, args, number) :- person(person, args, number)^(person=\"abc\") "; String xmlresults = Mediator.doQueryFromString(domainstr, querystr, srcstr, ); System.out.println(xmlresults);

20 FAQ on the Mediator 1) Do I need write Theseus plans for my sources? Not really. The mediator will generate them for you 2) I get syntax error when I run the mediator with my files? Check syntax of your files, usually its because Missing quote You used some editor that uses specialized quotes instead of double quotes You are missing ) or ^ 3) The mediator seems to sit and do nothing or returns no data? If you specified source plans, check and make sure that your source plans work If mediator is generating source plans use -no_plan_delete with the mediator and see that plans generated by the mediator are ok (most often problem is due to xquery for wrapper being slightly incorrect) Plans are in the C:\Documents and Settings\<user>\Local Settings\Temp directory

21 FAQ on the Mediator (Cont d) 4) I see ugly java exception that says something about parser error Check your domain model, you probably have a single quote instead of double quote or forgot to close double quote (Hopefully you will never really see this one) 5) I get empty result Turn on the debug mode and see the plans 6) More questions and answers will be posted as we get them from students. 7) Please do not include your domain model in the messages on the bulletin board 8) If we need your domain model to answer your questions, we will ask you to it to the TA separately

Introduction to Prometheus Mediator

Introduction to Prometheus Mediator What is Prometheus A data integration system capable of supporting Global-As-View Local-As-View Different types of data sources Wrappers, databases, web services Geospatial