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 the DDI 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?