Model-Driven Software Development - Web Abstractions 1

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

Course IN4308Master Computer Science

Delft University of Technology

Eelco Visserhttp://eelcovisser.org

Lecture 3

Wednesday, March 10, 2010

Application Model = Domain Model + Interaction Design

System

Domain Model = State?Interaction Design = Behaviour?


From high-level declarative model

System

automatically generate

Model

efficient & complete implementation


How to model applications?


Wat makes a blog?


Wat makes a webshop?


Wat makes a chair?


Wat makes a chair?


Purpose=>

Features

?


Application Model = Collection of UML Diagrams

generate implementation from model


- Consider

★ interaction styles

★ layout

★ color schemes

★ fonts

★ personalization

★ ...

- Parameters of the modeling language?

★ generic, orthogonal definition?

Details make the difference


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’


horizontal (technical) domains

vertical (‘business’) domains

DB

DM

UI

accounting


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

- Access control and more ...


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


<screenshot webdsl.org>


<screenshot researchr>


<screenshot tweetview>


<screenshot yellowgrass>


<screenshot department>


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 declarationproperty


object identifier

domain-specific type

Data Model for Wiki


page definition

page navigation (page call)

Page Definition & Navigation


Displaying Data

markup

rendering values


parameter

template definition

template call

Templates (Page Fragments)


wiki.css


data binding

pageflow

Modifying Data

submit


Core Wiki

navigate

actionWednesday, March 10, 2010

Core Wiki

navigate

actionWednesday, March 10, 2010

Creating Objects

find/create object by id


pass string

Modifying Data


Core Wiki

action

navigate creates page


Page Index


Output Object = Navigation


Output Object = Navigation

default definitioncustom 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

turn on access control

representation of principal


Principal

turn on access control

representation of principal


Authentication


Authentication


Authentication


Registration


Access Control Rules

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


Wiki Access Control Rules

‘only logged in users may edit pages’

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

create pages’










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, ...


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Model-Driven Software Development - Web Abstractions 1

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