ch 5 | System Modeling

Modeling component interaction helps to?

understand if a proposed system meets required system performance and dependability.

Event-driven modeling

1. show how the system reacts to external and internal events 2. based on the assumptions that a system have a finite number of states and the event transit the system from one state to another 3. real systems are event driven 4. example landline phone

System modelling helps to:

1. analyst to understand the functionality of the system 2.used to communicate with customers. 3.Used in documenting an existing system 4.used to generate a system implementation

Executable UML

make the complete automated transformation of models to code.

You create............... models of a system when you are discussing and designing the system architecture.

structural

stimuli as being of two types

1. Data Some data arrives that has to be processed by the system. 2. Events Some event happens that triggers system processing. (sometimes have associated data )

Structural models may be (two types) :

- static models: show the structure of the system design - dynamic models:show the organization of the system when it is executing.

Actors in a use case

may be people or other systems.

System modeling

the process of developing abstract models of a system, each model present different view of the system.

behavioral model

- models of the dynamic behavior of a system as it is executing. - They show what happens or what is supposed to happen when a system responds to a stimulus from its environment.

A sequence diagram shows :

- sequence of interactions that take place during a particular use case or use case instance. - The objects and actors involved are listed along the top of the diagram, with a dotted line drawn vertically from these. - Interactions between objects are indicated by annotated arrows.

Model-driven architecture (MDA)

1. an approach that is specific for implementation and design. uses a subset of UML diagram to describe a system. 2. create a different levels of abstraction 3. from a high level abstract model (platform independent model ) in principle its possible to generate a program form a model without any manual intervention

Types of model *MDA*

1. computation independent model (also domain model): model the important domain abstraction. 2. platform independent model: models the operation without the implementation. uses UML models which represent the static structure of the system and how it responds to external and internal events. 3. platforms specific model: transformation of the platform independent model. PCM for each application platforms. may be several layered for each PCM, each layer adds more platform specific detailed

Features of executable UML

1. domain models: identify the principle concern of the system (using UML class diagram and accusation between classes) 2. class model: represent each class is represent with its operation and attributes. 3. state model: where a state diagram is associated of each class model, represent the life cycle of the class. - to represent the dynamic behavioral of the system use object constraints language or UML action language.

Model-driven engineering (MDE)

1. is an approach in software development where the models is the principle output of the development process rather than programs. 2. the programs are generated automatically form the models. 3. the advocates says it increase the abstraction level of the MDE so the engineers doesn't have to worry about programming details

Data-driven modeling

1. primary driven by the data with little external events 2. show a sequence of action involved in processing input data and generating an associated output. 3. is a type of behavioral model

model-driven engineering *cons*

1. the models for abstraction doesn't mean its right for implementation 2. savings form generating the code could be outweighed by the cost of developing a translator for new platforms

model-driven engineering *pros*

1. the system in its higher level of abstraction 2. generating the code automatically means its cheaper to the system to adopt new platforms

State machine models

1.models to represent how the system react to external and internal events (therefore for real systems) 2. shows the system states as node. the event are races between nodes 3. statechart used to represent the state machine models.

System perspectives

An external perspective, where you model the context or environment of the system. An interaction perspective, where you model the interactions between a system and its environment, or between the components of a system. A structural perspective, where you model the organization of a system or the structure of the data that is processed by the system. A behavioral perspective, where you model the dynamic behavior of the system and how it responds to events. A Process perspective, where you model the use of system in business process.

..............and ................. may affect the decision on where to position system boundaries.

Social, organisational concerns

........................ may be used to define business process models.

UML activity diagrams

Context models

are used to illustrate the operational context of a system - they show what lies outside the system boundaries.

Each use case represents..?

discrete task that involves external interaction with a system.

data driven model is useful in?

during the requirement specification (show end-to-end system processing)

System boundaries

established to define what is inside and what is outside the system.

could the MDA be used in agile development?

generally speaking: *NO* because of the contradicts between agile development principles and MDA. but if a complete PIM is generated then in principle *YES*

Modeling system-to-system helps to?

highlights the communication problems that may arise

Modeling user interaction helps to?

identify user requirements

aggregation

one object (the whole) is composed of other objects (the parts). we use diamond shape

.................. and ............may be used for interaction modeling.

sequence diagrams Use case diagrams

State diagrams

show how the system reacts to internal and external events.

Sequence diagrams

show interactions between actors and the system and between system components.

Activity diagrams

show the activities involved in a data processing .

Use case diagrams

show the interactions between a system and its environment.

Class diagrams

show the object classes in the system and the associations between these classes.

Architectural models

show the system and its relationship with other systems.

Usage of model-driven engineering

still in the early stages. the effect on SW is unclear yet

Use cases were developed originally to ...?

support requirements elicitation