© Tata Consultancy Services ltd. April 18, 2023 1

Adopting MDA in a large IT consultancy organization – opportunities, challenges and

lessons learnt

Vinay Kulkarni* and Sreedhar Reddy, Tata Research Development and Design Centre, Pune, INDIA

vinay.vkulkarni@tcs.com

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It all began in 1994

Ground situation Crack design team

Functional Architectural

Shortage of experienced OO programmers

Lack of proven industrial-scale OO development methods

Lack of robust development tools

A core banking product To be delivered on state-of-the-art

technologies i.e. OO, 3-tier client-server architecture with OLTP monitor, rich GUI etc.

Customizable offering catering to purpose-specific choice of

Business functionality Business process Technology platforms like

RDBMSs, OLTP monitors and GUI platforms

Long life Off the shelf product or

bespoke solution

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Architectural prototype

A small team of experienced architects manually implemented a sample functionality covering all the layers of implementation architecture

Objectives Firm up broad architectural

decisions as regards scalability, throughout, response time etc

Familiarization with finer nuances of technology platforms

Lead to coding guidelines and best practices

Revelations Typical business logic has low

algorithmic complexity Several reusable design and

architectural patterns Architecture can be neatly

separated from business logic

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Intuition

Complete implementation

Business logic Solution architecture

Snippet1 Snippet2 Snippetk

Specification Specification1 Specification2 Specification3

Generate solution architecture specific code from its declarative specifications

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Our MDA approach - overview

A meta model captures a recurring code pattern All meta models defined in terms of a meta meta model A model based code generator is an interpreter of meta meta model

Application structure captured in extended UML models Business logic specified using a DSL Application specifications (i.e. PIM) are translated into a PSI using

PSM-specific code-generators that encode choice of design strategies, architecture decisions and technology platforms

Integrate independently generated code snippets in a consistent manner through an architecture

Component-based development process to manage size and facilitate independent development

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Example – a client/server application

Instance of

GUI layer code App layer code Db layer code

Composed fromApplication implementation

Decomposes intoApplication specification

GUI layer model App layer model Db layer model

GUI layer meta model App layer meta model Db layer meta model

View ofUnified meta model

Model to code transformation

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Our MDA approach - architecture as the integrating glue

MVC paradigm Well-defined interfaces Universal interface in the form of

services Object façade over relational

database Transactional integrity,

distribution transparency and scale-up courtesy middlewareDatabase

GUI

UI manager

Universal Interface

Application Services

DM

Application Server

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Our MDA approach - component based development

Model workspace

Codeworkspace

Component workspace

Workspace for sharing Application

release

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Model based code generation

Class definition Attribute handling logic Getter/Setter Default constructor and copy

constructor Persistence

Primary- and Alternate-key based CRUDE methods

Primary- and foreign-key based association handling

Design strategies Soft locking, Soft delete, Auditing,

Error handling, Trace logs

Object-wrapper for non primary-key based data accesses

Component deployment Bean class, Remote interface and

Deployment descriptor

Screen definition Layout Server-side interface Placeholder for Event logic

Testing support Look-n-feel Interaction with server-side

Testing support Unit test harness for a service, Test

data generation Build support

Makefiles

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Representative usage data

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In our experience

Product-lines and large projects adopted the approach

Technology-proofingIncreased productivityUniformly high code quality

Consistent implementation of design strategies, best practices, guidelines etc.

Prevention and early detection of errors

More complete testing of applicationEnhanced reusability

Small and medium sized projects didn’t find the approach attractive enough to adopt

High learning curvePerceived loss of controlCustomizing code generators takes

timeLess agile development process

Tight coupling with repositoryUnidirectional synchronization from

model to codeNo debugging support at model levelComplex versioning and configuration

management

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Addressing customizability of code generators

Model-based code generator

Model

Code

Generic code generator generator

Composition

d a t

d’ a’ t’

Selection

Repository of building blocks

D A T

Modification

Generates

Intuition - meta tools delivering tools

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Customizable code generators

A code generator is a hierarchical composition of building blocks

Building block is an unifying abstraction to specify [Aspect] Model Model transformation Model translation

Code generation is a three-step walk over the composition tree Model creation Model transformation Code weaving

Uses OMG QVT and OMG MTT standards

Base model Aspect model

Model to model transformation

Model to texttransformation

Text artefacts

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Code generation steps

Instantiation step Models are stamped out (leaf

level) Models are merged (non-leaf

level) Transformation step

Code fragments are generated (leaf level)

Weaving specifications are generated (non-leaf level)

Composition step Code fragments are weaved as

per the weaving specifications

Model2Java

Functionality Persistence

Object modelAttribute handling

OR map Audit

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In our experience

Building-block based restructuring of code generators led to Product-line of code generators Refined organization of development team as platform-experts,

architecture-experts etc. Smaller development team Reuse across product-lines

Thus Enabling definition of a software factory Removing the tools team as a bottleneck as the factory can be

instantiated elsewhere too

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Addressing high learning curve

Complete implementation

Business logic Solution architecture

Snippet1 Snippet2 Snippetk

Java Tag1 Tag2 Tag3

Generate solution architecture specific code from its declarative specification encapsulated in tags using a code-centric development approach

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Metadata-driven aspect-oriented development

Business logic with metadata Code fragments

Class model

Tag processor

Tag definitions

Weaver

Architect

Developer

The toolset is realized as a set of Eclipse plug-ins

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In our experience

Easy adoption by small to medium sized projects

No / low learning curveAgile loosely coupled development

processQuick turn-around time for a changeQuick development of purpose-

specific toolsAdherence to industry-standard

technologiesLeads to a repository of reusable

software artefactsGenerated application can be

effectively maintained simply with JDK

However,

A small project grows into a large project

A small offering acquires product-line nature over time

Large-sized projects are better managed with higher-level abstractions

Therefore,

A hybrid approach capable of supporting code-centric, model-centric and easy switching between the two seems called for.

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Merged approach

Business logic with metadata Code fragments

Annotated class models

Building block1

(for Tag1)

Weaver

MDD modelsModel to modeltransformation

Building block2

(for Tag2)Skeleton

building block

Code fragments Class definition

Metadata-driven aspect-oriented approach Model-driven development approach

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Summary

MDA delivers increased productivity, better code quality, platform independence and easier change management

Excellent for large projects and product-lines Metadata-driven aspect-oriented approach seems to suit

small and medium-sized projects better Need to evolve suitable development methods that allow

MDA to be adopted in a more flexible and incremental manner than all-or-nothing top-down manner

Proposed an approach to address this pertinent need

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Questions?