INTRODUCTION TO DSSA DSSA is basically ‘Software Architecture focused on a
particular domain.’
Why is it focused to a particular domain? a) To constraint the problem space b) Facilitate focused development
DSSA is a collection of structures of the system which comprise of:
a) Software elements b) Externally visible properties of those elements c) Relationship among those components
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Applications of DSSA
The process of developing and implementing
a DSSA is called domain engineering.
The process of developing an
application based on a
DSSA is called application
engineering.
D S S A
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Problem Space & Solution Space
. .
. . .
Problem Space
General Solution Space
Problem Space divided as per the domain
. .
. .
?
General Solution Space divided as per the domain
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DSSA Components
(Classification of requirements)
Domain Model
• Defines the behaviour of applications in the system. • Standardizes the domain terminologies & provides the system data flow. • Provides standardized descriptions of problems to be solved in the domain.
Reference
Requirements
• Supports the design of the reference architecture. • Divides the customers requirement into functional and non-functional
components. • The requirements may be mandatory, optional or variable.
Reference
Architecture
• Describes a general computational framework. • Represents a set of principal design decisions simultaneously applicable to
multiple related systems. • Includes explicitly defined points of variation.
(Collect info. about the domain)
(Develop a generalized framework) GNDU, Amritsar [M.Tech. Software Systems 2012-2014 batch]
DSSA Components(cont.)
Domain Model
Problem Space
The problem space is simplified through the creation of a domain model.
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Reference Architecture
Reference Requirements
Solution Space
DSSA Components(cont.)
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Main Advantages of DSSA
• The overall cost is minimized as the assets can be reused.
• The market share of the
organization can be increased by developing related applications for different users.
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MODULE 1: DOMAIN MODEL
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Domain Model Before the requirements can be determined, it is necessary to understand the characteristics of the system. Domain model: Defines the behaviour of applications in the
system Standardizes the domain terminologies &
provides the system data flow. Provides standardized descriptions of problems
to be solved in the domain. Provides the vocabulary to formulate the
reference requirements.
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Components of the Domain Model
Scenarios Domain Dictionary Context/Block Diagram Entity-Relationship Diagram Object Model Data Flow Model State Transition Models
Information model
Operational model
Feature model
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Scenario Scenarios are a list of events which are helpful in eliciting the requirements from the customer in an informal manner.
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Domain Dictionary It consists of the explanation of the terms used in the scenarios and the customer needs statement. Example:
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Context Information Diagram
It describes the high-level data flow between the major components in the system.
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Entity/Relationship (ER) Diagram
Represents the aggregation and generalization relationships between entities.
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Object diagram An object-oriented approach is followed to identify the objects which are mentioned along with their attributes and operations.
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Data-Flow Diagram It focuses on the data exchanged within the system, with no notion of control.
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State-Transition Diagram
It describes the events and states that take place in the domain.
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MODULE 2: REFERENCE REQUIREMENTS
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Reference Requirements
Reference requirements are responsible for identifying the portion of solution space that the domain model (problem space) will map into. Reference Requirements: Support the design of the reference architecture. Divides the customers requirement into functional
and non-functional components. The requirements may be mandatory, optional or
variable. Constrains the architecture and the implementation.
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Components of Reference Requirements
Functional Requirements Non-functional Requirements Design Requirements Implementation Requirements
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Functional Requirements Describes the functions to be performed as per the domain .
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Non-Functional Requirements Example: Security, Performance, Reliability.
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Design Requirements
Example: Architecture style, User interface style.
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Implementation Requirements
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MODULE 3: REFERENCE ARCHITECTURE
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Reference Architecture Perquisites
There are no predefined standards for designing the reference architecture
• This is one of the reasons, that it is supported by an extensive documentation.
Architecture does not define implementation
• The architecture establishes constraints on downstream activities, and those activities must produce finer-grained designs and code that are compliant with the architecture.
Architecture is design but not all design is architecture
• There are many design decisions that are left unbound by the architecture, and are happily left to the discretion and good judgment of downstream designers and implementers.
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Reference Architecture Perquisites
‘Design’ is a general term, don’t confuse it with ‘System Design’ , which refers to the in-depth view of the structure of the system.
An ‘architecture’ is a reusable design and a ‘reference architecture’ is a reusable design for a family of systems in a particular domain.
Reference Architecture Model can also be called as the architectural style of the system which may be layered, pipe and filter etc.
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Reference Architecture It is a generic architecture focused on fundamental abstractions of the domain. • Describes a general computational
framework based on the chosen architectural style.
• Represents a set of principal design decisions simultaneously applicable to multiple related systems.
• Includes explicitly defined points of variation.
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Architecture Hierarchy
Reference Architecture
• First, a generalized architecture is selected.
Application Specific
Architecture
• Using the reference architecture, an application specific architecture is created.
Implementation
• The implementation of the architecture is carried out.
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Components of Reference Architecture
Reference Architecture Model Configuration Decision Tree Architecture Schema Dependency Diagram Component Interface Description Constraints Rationale
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Reference Architecture Model
All designs start out with some simple abstraction based on the architecture style.
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Configuration Decision Tree
A subset of reference requirements is chosen and a configuration decision tree is made accordingly. Configuration is done at reference architecture instantiation time.
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Architecture Schema
Name/Type
Description
Reference requirements satisfied
Data flow and control flow diagrams
Design rationale Interface and architecture
specifications and dependencies
It is a collection point for knowledge about the components that make up a DSSA.
All such details are to be listed for every component involved. GNDU, Amritsar [M.Tech. Software Systems 2012-2014 batch]
Dependency Diagram The reference architecture dependency diagram reveals component connections at a level of granularity reflecting the architectural style chosen by the system architect.
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Component Interface Description The focus is on, how elements interact with their environments, not on how elements are implemented. An Interface Description Language(IDL) is used to describe the interface as per the syntax of the language chosen.
Ex: LILENNA
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Constraints
Constraints are the ranges of parameter values, relationships between parameter values or components etc. which have to be considered throughout the development of a system.
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Rationale
Rationales capture the motivation behind various decisions, such as the partitioning of the system into discrete elements and the formation of the architecture in terms of connecting elements. Rationales are inferences that can be structured as an argument with the design decision being the conclusion. GNDU, Amritsar [M.Tech. Software Systems 2012-2014 batch]