A Multi-theory Logic Language
for the World Wide Web
Giulio Piancastelli and Andrea Omicini
24th International Conference on Logic Programming (ICLP 2008)
Udine, December 9-13, 2008

Purpose
Bring principles, abstractions,
and insights from the Web
architecture to research on the
use of logic programming for Web
application prototyping

Resource
Any conceptual target of a
hypertext reference
Composed of:
• identifier (URI)
• data
• behavior

http://example.com/sales/2004/Q4

http://example.com/sales/2004/Q4
R
T(R)
f(a).
r(P, Q) :-
s(P), t(Q).

http://example.com/sales/2004/Q4
http://example.com/sales/2004/
R
R1 T(R)
T(R1)

http://example.com/sales/2004/Q4
http://example.com/sales/2004/
R
http://example.com/sales/ R1 T(R)
R2 T(R1)
T(R2)

http://example.com/sales/2004/Q4
http://example.com/sales/2004/
R
http://example.com/sales/ R1 T(R)
R2 T(R1)
T(R2)

http://example.com/sales/2004/Q4
http://example.com/sales/2004/
R
http://example.com/sales/ R1 T(R)
R2 T(R1)
T(R2)
R
http://example.com/sales/Q42004/

Implicit Resources
Resources representing recurring
concepts in Web development that
are always attached to the bottom
of any context
• the session with the application
• the user
• the application itself
• the deployment environment

HTTP
GET /sales/2004/Q4 HTTP/1.1
Host: example.com

HTTP
GET /sales/2004/Q4 HTTP/1.1
Host: example.com
Method Information: how the
receiver has to process the
request
'/sales/2004/Q4' : get(Request, Response, View).

HTTP
GET /sales/2004/Q4 HTTP/1.1
Host: example.com
Scope Information: the data
where the receiver should
operate the method
'/sales/2004/Q4' : get(Request, Response, View).

/r2/r1/r
R
T(R)
get(_, _, V) :-
a, b, c(V).
a :- p, q, r.

/r2/r1 /r2/r1/r
R1 R
T(R)
get(_, _, V) :-
a, b, c(V).
a :- p, q, r.

/ /r2 /r2/r1 /r2/r1/r
root R2 R1 R
T(root) T(R)
p :- x, y, z. get(_, _, V) :-
x. a, b, c(V).
a :- p, q, r.

/ /r2 /r2/r1 /r2/r1/r
root R2 R1 R
T(root) T(R)
p :- x, y, z. get(_, _, V) :-
x. a, b, c(V).
a :- p, q, r.

Dynamic Resource
Behavior (1)
Two or more URIs can be
associated to the same resource:
resources may live in different
contexts at the same time and
feature different behavior
according to the context where
the computation takes place.

Dynamic Resource
Behavior (2)
Behavioral rules are expressed as
first-class abstractions in logic
programming languages, where
programs can be treated as data:
the HTTP protocol allows changing
resource data by using the PUT
method, so that runtime
behavioral changes of a resource
in a context are possible.

A Multi-theory Logic Language
for the World Wide Web
Giulio Piancastelli and Andrea Omicini
24th International Conference on Logic Programming (ICLP 2008)
Udine, December 9-13, 2008