DDI & Model-View-Controller:

An Architectural Perspective

Dennis Wegener, Matthäus

Zloch, Thomas Bosch (GESIS)Dagstuhl, 23.10.2012

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Overview Architecture Missy/StarDat

Presentation

Business Logic

Abstract Persistence

MVC

Persistence

Software Management - Maven & GIT

• Apache Maven– software project management and comprehension tool

• Maven Modules for data modelling in our projects:– Abstract module for DDI (based on DDI ontology)

– Concrete modules for each project that• Inherit from abstract ddi module

• Add project-specific data fields

• Sharing via VersionControlSystem– Project sources in internal VCS (GESIS-SVN)

– Data Module shared externally (GIT)• https://github.com/missy-project/ddi-model

DDI model

DDI model+ Missy

Extensions

DDI model+ StarDat

Extensions

Missy Maven Structure

Data model & presentation - MVC

• MVC design pattern

• Model – Domain classes

– Attributes

– Relations

• View– Representation

– JSP, Velocity, XML, JSON, …

• Controller– Commands

– RESTful interface

RESTful interface

• Well-defined interface based on HTTP– With few basic methods: GET, POST, PUT, DELETE

– Response codes (e.g. 200 OK, 404 Not Found)

– Data supported described by MIME types (e.g. text/xml, application/json)

• Resources are identified using URIs– Collection URI (like http://missy.org/studies)

– Element URI (like http://missy.org/studies/studyZA1000)

• Resources could map to domain classes / entities of theDDI ontology

Data model & persistance – API

• Once you have the model you can…– Generate views / user interfaces

– Generate storage model (in RDB via hibernate)

• Abstract persistance API– To be published …

• Concrete Implementations– Relational DB

– DDI XML files

– …

Missy Example

• Question:– DDI Ontology: class Question,

fields like dcterms_identifier, …, field question text

• Variable:– DDI Ontology: class Variable,

fields like dcterms_identifier,…

– Missy: inherits class Variable, adds fields variable name, variable label, classification, …

• Relation: – Variable * hasQuestion 1 Question

– Defined at level of DDI Ontology

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Missy Extension

DDI Ontology

Key Messages & Questions

• DDI model implemented as abstract data model in OO programming language

– According to MVC - domain classes with attributes & relations

– Do we need a standard REST interface?

• DDI model not directly based on XML representation– „Data model vs. Data format“

– Export mechanisms for XML based representation

• DDI model integrated into project‘s architectures– Does it make sense to create a reference architecture?

• Reuse of software modules is possible– We already share modules/code between internal projects Missy & StarDat

– Is anyone else interested in sharing?