Overview of Prometheus Mediator Snehal Thakkar CSCI 548 - - PowerPoint PPT Presentation

Overview of Prometheus Mediator

Snehal Thakkar CSCI 548 Information Integration On the Web

Outline

Prometheus mediator

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

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

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

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

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

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!!

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, “http://....”)

Rules

Datalog rules Relationships between domain concepts and sources Domainrel1(x, y, z) :- source1(x ,y)^ source2(y, z)

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”)

Examples

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: employee(name, dept, sal) :- s1(name, dept, sal)

Table Name Database Name Domain Predicate Attribute Names

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>

Example of using a wrapper

SourceSchemas: wrapper1(Address:string:b, Parcel:string:f,

Owner:string:f, Addr:string:f, Desc:string:f)

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,

"http://oceanus.isi.edu:8080/agent/runner?plan= wra pper1%2Fplans%2Fproduction")

Rules: ….

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

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”)

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:

Example

Source file s1(name, dept, sal) :-

employee(name, dept, sal)

Source Name Domain Predicate

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);

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);

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

• ften problem is due to xquery for wrapper being slightly incorrect)
• Plans are in the C:\Documents and Settings\< user> \Local Settings\Temp

directory

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 email it to the TA separately