DexterA Browser-based Data Explorer for End Users

Sudhir Agarwal, Abhijeet Mohapatra, and Michael Genesereth

Stanford Logic Group

Project Page: http://dexter.stanford.edu

Motivation Which Republican senators have

been fined by the FEC?

Name State …

Barbara Boxer CA …

Ted Cruz TX …

congressMembersAd-hoc analysis

More and more structured data made available in the Web

Ad-hoc Analysis of Data

• Too tedious:

• Limited querying capability of sources

• Spreadsheets don’t offer sufficient functionality

• Inability to query private and public data together without uploading the data

http://dexter.stanford.edu

Browser-basedDomain-independent

Explorer for structured data

Ad-hoc “on-the-fly” queries Queries across multiple sources

Dexter

Data = Tables• Tables

• Other sources of data (are mapped to tables)

• CSV, JSON or XML files

• APIs

• DOM elements in Web pages (e.g. <div>, <table> elements)

X Y1 a2 b

rY Za 3c 5

s

Queries = Dexlog Rules

Dexlog = Datalog + Negation (as failure) + Aggregation + Built-ins

X Y1 a2 b

rY Za 3c 5

s

q(X, Z) :- r(X, Y) & s(Y, Z)

Overview: http://dexter.stanford.edu/main/dexlog.html

Aggregation: Special operator setof() for constructing sets

setof(X, r(X, Y), S) ≡ SY = {X | r(X, Y)}

Which Republican senators have

been fined by the FEC?

Example: Ad-hoc Analysis

• Data about administrative fines: http://www.fec.gov/data/AdminFine.do

• Data about members of Congress: https://www.govtrack.us/api/v2/person [Govtrack API]

• Filter misc.fines to get senators who have been fined • Filter misc.congress to get republican members • Join the two filtered tables on member names

Dexlog query to join the two tables: misc.fines and misc.congress

Demo

Query Evaluationq(X, Z) :- govtrack.s(X, “Republican”) &

fec.t(X, “senator”)

Dexter

Query Decomposition

govtrack

Query Evaluationq(X, Z) :- govtrack.s(X, “Republican”) &

fec.t(X, “senator”)

Dexter

fec.t(X, “senator”)

govtrack.s(X, “Republican”)

Source Invocation

govtrack

Query Evaluationq(X, Z) :- govtrack.s(X, “Republican”) &

fec.t(X, “senator”)

Dexter

fec.t(X, “senator”)tuples

govtrack.s(X, “Republican”)tuples⋈

Answer Construction

govtrack

• Browser for supporting ad-hoc queries over structured data

• Create tables (from files, Web pages, DBs, APIs), edit tables, check integrity constraints, query tables using Dexlog rules, visualize tables as charts, share and export tables and rules

• Resources:

• Dexter: Plugging-n-Playing with Data Sources in Your Browser [AAAI ’14 workshop on Semantic Cities]

• Project page: http://dexter.stanford.edu

• Primer: http://dexter.stanford.edu/primer.pdf

• Dexlog Overview: http://dexter.stanford.edu/main/dexlog.html

Dexter