1. Deco — Declarative Crowdsourcing
Scoop — The Stanford – Santa Cruz Project for Cooperative Computing with Algorithms, Data, and People
Hector Garcia-Molina, Aditya Parameswaran, Hyunjung Park, Alkis Polyzotis, Jennifer Widom
Stanford and UCSC

2. Same as everyone else’s…
The Big Picture
Same as everyone else’s…
Declarative queries
DBMS like thing
Web

3. The Big Picture Same as everyone else’s… DBMS like thing WSQ/DSQ
Declarative queries
WSQ/DSQ
[Goldman & Widom, SIGMOD 2000]
DBMS like thing
Web

4. Primary Focus (distinguishing features?)
Theoretical foundations
Generality / flexibility
Query optimization
We’re pretty sure other proposed models are instances of ours; let us know.

5. The Deco Data Model Goals for a new data model
(shamelessly stolen from myself)
Well-defined
Understandable
Sufficiently expressive (and not more)
Similar to existing models
Implementable

6. The Deco Data Model RDBMS Conceptual schema Actual schema Schema End
designer
End
user
relations and
other stuff
relations
Conceptual schema
automatic (system)
Actual schema
RDBMS

7. Rest of This Presentation
1. Small motivating example
2. “Relations and other stuff”
3. Mapping from conceptual schema to actual schema
4. Semantics: “valid instance” (actual to conceptual)
Not included in presentation
Enough examples, especially data
Normal forms (BCNF/4NF)
Metadata/annotations
Various details…
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

8. Small Example ⋈ 1. Fetch 2. Resolve 3. Join restaurant rating cuisine
Chez Panisse
4.9
French
California
Bytes
3.8
• • •
1. Fetch
2. Resolve
3. Join
User
view ⋈ o
resolution
rule
resolution
rule
restaurant
Chez Panisse
Bytes
• • •
restaurant
rating
Chez Panisse
4.8
5.0
4.9
Bytes
3.6
4.0
• • •
restaurant
cuisine
Chez Panisse
French
California
Bytes
• • •
Anchor
fetch rule
Chez Panisse
Bytes
fetch rule
French
Dependent
Dependent
fetch rule
fetch rule

9. Relations and other stuff
Attributes designated as anchor or dependent
Resolution rules — dealing with uncertainty
Fetch rules — “access methods” to externally obtained data
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

10. Relations and Attributes
R (restaurant, address, rating, cuisine) S (address, city, zip)
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

11. Relations and Attributes
R (restaurant, address, [rating], [cuisine]) S (address, [city, zip]) [dependent attribute groups]
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

12. Relations and Attributes
R (restaurant, address, [rating], [cuisine])
S (address, [city, zip])
[dependent attribute groups]
anchor attributes
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

13. Resolution Rules R (restaurant, address, [rating], [cuisine])
S (address, [city, zip])
One resolution rule per dependent attribute-group
restaurant,address  rating (F=avg)
restaurant  cuisine (F=dup-elim)
address  city,zip (F=majority)
LHS  RHS with (black-box) function F
Given LHS values and one or more
RHS values, F returns zero or more
(new) values for RHS
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)
Each resolution rule imposes an MVD on the conceptual schema. If the resolution function guarantees to return exactly one value, then the MVD is also an FD.

14. Fetch Rules R (restaurant, address, [rating], [cuisine])
S (address, [city, zip])
LHS  RHS with procedure P
Given LHS value, procedure P can obtain RHS values
from external source(s)
restaurant,address  rating
restaurant  cuisine
address  city,zip
rating  restaurant,address
cuisine  restaurant,address
rating,cuisine  restaurant,address
  restaurant,address
  anchor attributes
(subset of) anchor  dependent group(s)
dependent group(s)  anchor
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

15. Conceptual Schema (end user)
R (restaurant, address, rating, cuisine) S (address, city, zip)
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

16. Actual Schema R (restaurant, address, [rating], [cuisine])
S (address, [city, zip])
restaurant,address  rating
restaurant  cuisine
address  city,zip
One RR per dependent attribute-group
“Deco tables” [decomposed]
One for anchor attributes
One for each resolution rule
A1(restaurant, address)
A2(restaurant, address, rating)
A3(restaurant, cuisine)
A4(address)
A5(address, city, zip)
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)
Deco tables are a 4NF decomposition based on the MVDs imposed by the RRs. If the MVD is also an FD, the FD may not hold in the Deco table.

17. Actual Schema + R (restaurant, address, [rating], [cuisine])
S (address, [city, zip])
restaurant,address  rating
restaurant  cuisine
address  city,zip
One RR per dependent attribute-group
Fetch Rules ― add tuples
Resolution Rules ― resolve uncertainty
(for query result)
A1(restaurant, address)
A2(restaurant, address, rating)
A3(restaurant, cuisine)
A4(address)
A5(address, city, zip) +
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)
Deco tables are a 4NF decomposition based on the MVDs imposed by the RRs. If the MVD is also an FD, the FD may not hold in the Deco table.

18. Valid Instance of Database
Given:
Current contents of Deco tables (actual schema)
Fetch Rules and Resolution Rules
Valid instance (conceptual schema) is any state of relations obtained by:
1. Fetch — add tuples to Deco
tables by invoking FR procedures
2. Resolve — resolve dependent
attributes using RR functions
3. Join — full outerjoin of Deco
tables for each relation
RDBMS
Actual schema
Conceptual schema
Schema
designer
relations and
other stuff
End
user
relations
automatic (system)

19. Small Example ⋈ 1. Fetch 2. Resolve 3. Join restaurant rating cuisine
Chez Panisse
4.9
French
California
Bytes
3.8
• • •
1. Fetch
2. Resolve
3. Join
User
view ⋈ o
resolution
rule
resolution
rule
restaurant
Chez Panisse
Bytes
• • •
restaurant
rating
Chez Panisse
4.8
5.0
4.9
Bytes
3.6
4.0
• • •
restaurant
cuisine
Chez Panisse
French
California
Bytes
• • •
Anchor
fetch rule
Chez Panisse
Bytes
fetch rule
French
Dependent
Dependent
fetch rule
fetch rule