Model-Driven Software Development - Web Abstractions 1

Web Abstractions 1
data models, user interface templates, access control

Lecture 3

Course IN4308
Eelco Visser
Master Computer Science
http://eelcovisser.org Delft University of Technology
Wednesday, March 10, 2010

Application Model = Domain Model + Interaction Design

System

Domain Model = State?
Interaction Design = Behaviour?

From high-level declarative model Model

automatically generate

efﬁcient & complete
implementation System


How to model applications?


Wat makes a blog?


Wat makes a webshop?


Wat makes a chair?


Purpose
=>
Features
?

Application Model = Collection of UML Diagrams

generate implementation from model

Details make the difference

- Consider
★ interaction styles
★ layout
★ color schemes
★ fonts
★ personalization
★ ...

- Parameters of the modeling language?
★ generic, orthogonal deﬁnition?


UI programming is like assembly programming

concerned with screen components

not with interaction styles & concepts

want: declaration of user interaction


Problem: ‘UI tweaking’

- code generation produces standardized/limited UI

Alternative: extra ‘hand coding’
e.g. UI templates not part of model

Conclusion:
- modeling not adequate for interaction design
- user interface programming is low-level

instead of a general purpose solution (UML)

address speciﬁc class of software systems


Intermediate Goal for MDSD

develop better programming abstractions

for horizontal domains

before tackling vertical domains

‘let’s ﬁrst make it easier to build web apps’

vertical (‘business’) domains

UI

DM

DB

accounting horizontal (technical) domains

Properties of Domain-Speciﬁc Languages

DSL design requires tradeoff between
- Expressivity
- Coverage
- Portability
- Interoperability
- Completeness
- Maintainability
Extensive discussion in Quarter 4


The Web Domain


browser server database

app.war

a web application lives on the server

Concerns in Web Programming

- Persistent data
★ data integrity
★ search

- User interface
★ data validation
★ styling, layout
★ navigation
★ actions

- Workﬂow
d mo re ...
- Access control an

Problems in Web Programming

- Separate language for separate concerns
★ (that’s good)

- Lack of integration
★ no consistency checking
★ different language styles

- Low-level conﬁguration
★ boilerplate code


WebDSL
a domain-speciﬁc language for web applications

separation of concerns & linguistic integration


Web Abstractions
from a declarative point of view
(we’ll investigate underlying mechanisms later)

Eelco Visser. WebDSL: A Case Study in Domain-Speciﬁc Language Engineering. GTTSE 2008: 291-373


Data Model Deﬁnition

entity declaration
property


Data Model for Wiki

object identiﬁer

domain-speciﬁc type


Page Deﬁnition & Navigation

page navigation (page call)

page deﬁniti
on

Displaying Data

rendering values

markup


Templates (Page Fragments)

template deﬁnition

template call
parameter


wiki.css


Modifying Data

data
binding

submit

page
ﬂow

Core Wiki

navigate

action

Creating Objects

ﬁnd/create object by id


Modifying Data

pass string


Core Wiki

navigate creates page

action

Page Index


Output Object = Navigation


Output Object = Navigation

custom deﬁnition default deﬁnition


Access Control

Danny M. Groenewegen, Eelco Visser. Declarative Access Control for WebDSL:
Combining Language Integration and Separation of Concerns. ICWE 2008: 175-188


Principal

representation of principal

turn on access control


Authentication


Registration


Access Control Rules

‘may access page f with
argument x if boolean
expression e is true’


Wiki Access Control Rules

‘anyone can view
existing pages, only
logged in users can
create pages’

‘only logged in users may edit pages’


Wiki Access Control Rules


More Web Abstractions

- Access control policies
★ constraints over objects
★ role-based AC, discretionary AC

- Data validation
★ form validation
★ data integrity

- Loading/accessing templates (partial pages)
★ (AJAX)

- Search
- Workﬂow


The Future of Quarter 3

- Lecture 4
★ More web abstractions

- Lecture 5
★ What does WebDSL abstract from?
★ Or: from DSL to Code

- Lecture 6
★ Language workbenches
★ Grammars

- Lecture 7
★ Language modeling


Schedule
Lab this week
★ Finish & submit proposal Design 1
★ Entity declarations
★ Basic setup for user interface

Cases
★ Case 1: domain analysis in digital library domain
★ Case 2: web abstractions

Next
★ Week 4 is ‘spring’ break; Week 5: lecture no, lab yes
★ Week 6: access control policies, validation, search, ...


Model-Driven Software Development - Web Abstractions 1

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