Browser-Based Enforcement of Interface Contracts in Web Applications with BeepBeep (Talk @ CAV 2009)

Browser-based Enforcement of
Interface Contracts in Web Applications
with BeepBeep

Sylvain Hallé, Roger Villemaire

University of California Université du Québec à Montréal
Santa Barbara, USA Montréal, CANADA

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Some web services

E-Commerce Service
Compute Cloud

PayPal API: billing, express checkout

Shopping: like Amazon
Google Search, Google Maps, GMail, ...

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Using web applications

MyApplication.com

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i ? MyApplication.com

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i ? MyApplication.com

1.

2.
...

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XML request
<ListItems> MyApplication.com
<title>birds</title>
</ListItems>

<Items>
<Item>
<ID>1</ID>
<Title>abc</Title>
</Item>
... XML
</Items>
response

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2

MyApplication.com

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2

MyApplication.com

c

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XML request
<cartCreate> MyApplication.com
<item>2</item>
</cartCreate>

<cart>
<id>c</id>
<items>
<item>2</item>
</items>
</cart> XML
response

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2

c MyApplication.com

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Constraints on the message trace

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i ?

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i ?
1.

2.
...

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2

i ?
1.

2.
... c

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2 2

i ?
c
1.

2.
... c

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You cannot add the same item twice
to the shopping cart
2 2

i ?
c
1.

2.
... c

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2 2

i ?
c ???
1.

2.
... c

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???

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2 2

c

! Atoms are properties over messages...

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G ( 2
Þ ØF
2

c
(
! + LTL operators...

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(
G "i
i
Þ ØF
i

c
(
! + quantification on elements

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(
G "i
i
Þ ØF
i

c
(
! + quantification on elements } LTL-FO+

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Enter BeepBeep

MyApplication.com

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Enter BeepBeep

(
G "i
i
Þ ØF
i

c
(
MyApplication.com

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Enter BeepBeep
2

MyApplication.com

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Adding BeepBeep to a real application

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Œ Copy BeepBeep to application folder
http://beepbeep.sourceforge.net

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Include BeepBeep

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Include BeepBeep

myapplication.html
<html>
<head>
<title>My Application
</title>
<script type="text/javascript"
href="myapplication.js"/>

</head>
<body>
...
</body>
</html>

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Include BeepBeep

myapplication.html
<html>
<head>
<title>My Application
</title>
href="beepbeep.js"/>
</head>
<body>
...
</body>
</html>

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Include BeepBeep

myapplication.html myapplication.js
<html>
<head> // Initializations
<title>My Application ...
</title>
<script type="text/javascript" req = new XMLHttpRequest();
<script type="text/javascript" ...
</head> function abc()
<body> {
... ...
</body> req.send(some_message);
</html> }

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Include BeepBeep

myapplication.html myapplication.js
<html>
<head> // Initializations
<title>My Application ...
</title>
<script type="text/javascript" req = new XMLHttpRequestBB();
<script type="text/javascript" ...
</head> function abc()
<body> {
... ...
</body> req.send(some_message);
</html> }

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Ž Obtain (or create) a contract file with LTL-FO+ formulae
# ---------------------------------------------------------------
# BeepBeep contract file for the Amazon ECS
# ---------------------------------------------------------------
% To create a cart, you must put at least one item
; G ([x1 /CartCreate/Operation] (((x1) = ({CartCreate})) ->
(<x2 /CartCreate/Items/Item/ASIN> ({TRUE}))))

% You can only create a cart once
; G ([x1 /CartCreate/Operation] (((x1) = ({CartCreate})) ->
(X (G (!(<x2 /CartCreate/Operation> ((x2) = ({CartCreate}))))))))
% No CartAdd can occur before a CartCreate
; (!(<x1 /CartAdd/Operation> ((x1) = ({CartAdd})))) U
(<x2 /CartCreate/Operation> ((x2) = ({CartCreate})))
% You cannot add the same item twice to the shopping cart
; G ([i /CartCreate/Items/Item/ASIN] (X (G
([j /CartAdd/Items/Item/ASIN] (!((i) = (j)))))))

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Experimental results

Sample property: "each car entering in a parking lot must exit
before entering again"

< 5 ms/msg.
Time per message (ms)

Trace length

Hallé & Villemaire, EDOC 2008

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Simultaneous monitoring of 11 properties (Amazon example)

20
< 5%
Time difference (%)

10

Moyenne
0

-10

-20
0 20 40 60 80 100 120 140 160 180 200

Trace length

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Simultaneous monitoring of 11 properties (Amazon example)

14
Time per message (ms)

12
Data domain
10
25
8
200
6
4
2
0
0 20 40 60 80 100 120 140 160

Trace length

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Take-home points

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Take-home points

1. Constraints involving temporal operators and quantification
on message contents arise naturally in real web applications

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Take-home points


2. An extension of LTL can formalize them: LTL-FO+

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Take-home points



3. Runtime monitoring of these constraints can be done
efficiently, even with quantification

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Take-home points



3. Runtime monitoring of these constraints can be done
efficiently, even with quantification

4. BeepBeep is a tool that allows it with
minimal modifications on real applications

http://beepbeep.sourceforge.net/

Sylvain Hallé

Browser-Based Enforcement of Interface Contracts in Web Applications with BeepBeep (Talk @ CAV 2009)

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