Steps for Designing a system from scratch

You are into a new project, and provided with some requirements. How would you go about designing the new system

We are in this situation a lot of times. So here I am trying to create a step by step guide from taking a requirement doc to finalizing a system architecture.

Stage 0: Before getting started with the design process, we need to make sure about the following.

– Do we have clear understanding of requirements?
– Are we creating something from scratch or enhancing and existing system. In later case we will have design and technology constraints from previous system?
– Have we identified non functional requirements- security, performance, availability etc.
– Have we identified all stakeholders and their role?
– Have we identified key players that will help in creating architecture (architects, Business Analysts, Product owners)
– Have we decided on time/ money to spent on design activities?
– Have we identified reference material? Do we have artifacts for similar design problems, from either inhouse or external sources?
– How are we going to maintain the design artifacts- wiki, git, svn, confluence etc. We will need to maintain versioning?
– Have we identified any guiding principles for the design- we will use open source softwares and tools, or we will be using linux system of deployment etc.
– Are there any constraints- say client wants to use any specific third party tools or technologies, any specific compliance required by law (multilingual support), service availability grantee
– Have we identified all third party systems with which our system will interact and how the interaction will be done?
– Are we creating the system in one go or will it be a phased delivery. Have we identified the value add provided by various components being built and prioritized the delivery?
– In case of phased delivery, we need to identify scope of each phase?
– Have we identified risks involved and mitigated them?
– If we are modifying or enhancing an existing system, we need to understand what areas can be reused, enhanced and built from scratch?
– Better to create a formal document to identify what all design artifacts are required.
– Define KPIs (Key performance indicators) and SLAs (Service Level Agreements)
– Have we defined acceptance criteria for the design?

Stage 1: Now we need to understand the business and what changes do we need.

– Have we understood organization structure?
– Have we identify business goals and objectives for the organization and what changes are required?
– Identify all business requirements, for example customer should be able to return a product is a business requirement.
– Identify and design current business processes (How current business work, does it fulfill all the business requirements or not, if yes, do we need to change or enhance the way it is being done right now, for example current purchase process is manual and we want to provide online options.)
– Identify changes or modification required in business processes

– Design artifacts to be delivered in this stage
Catalogs
— Organizations
— Actors
— Goals
— Roles
— Business Services
— Locations
— Process / Products
Matrices
— Business interaction
— Actor/ Role
Diagrams
— Business Services
— Functional Decomposition
— Product/ Process lifecycle
— Goal/ Service diagram
— Business Use cases
— Process Flow
— Event diagram

Stage 2: Focus on Data used

– What data is being used in the application? how it is originated and used?
– How the data is shared securely in enterprise
– Create common vocabulary and data definitions
– Identify security measures to be taken

– Design artifacts to be delivered in this stage
Catalogs
– Data Entities

Matrices
– Data Entity/ Business function
– Data Entity/ Application matrix

Diagrams
– Conceptual Data Diagram
– Logical Data Diagram
– Physical Data diagram
– Data lifecycle diagram
– Data Security diagram
– Data migration diagram

Stage 3: What all Applications are available? Changes required and new ones to be created

Application- Core parameters
– Platform independence
– Easy to use
– Identify existing applications and newly ones to be created at logical level and than map to physical level

– Design artifacts to be delivered in this stage
Catalogs
– Application portfolio
– Interface catalog

Matrices
– Application/ Organization
– Role/ Application
– Application/ Function
– Application/ Interactions

Diagrams
— Application communication
— Application and user location
— Application use case
— Application details – components/ modules and services
— Application details – Layered architecture if used

Stage 4: Understand the technology working behind the scenes

Control technical diversity: Minimizes cost of expertise.

Catalogs
— Technology portfolio

Matrices
— Application/ Technology

Diagrams
— Deployment diagram
— Environments and locations
— Communication engineering diagram (firewalls)

Stage 5: Lets consider Non Functional Requirements
— Security
— Performance
— Availability
— Disaster recover
— Data backups
— Others (Project specific)

Stage 6: Post Design phase:

– Did we identify reusable artifacts and services which can be used by other projects?
– Have we conducted periodic validation that design and product being build are in sync?
– Does the design change due to any change requests? Has that been reflected in design?
– Have we met all the acceptance criteria that were set initially?

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