Analysis ModelingAnalysis ModelingChapter 12

DFD , ERD DFD , ERD TopicsTopics

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Who does Analysis Who does Analysis Modeling?Modeling?

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Why Analysis Why Analysis Modeling?Modeling?

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Analysis ModelAnalysis ModelAnalysis Modeling

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Analysis Model

Structure of Analysis Model

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Analysis ModelAnalysis ModelThe analysis model must achieve

three primary objectives

◦to describe what the customer requires,

◦to establish a basis for the creation of a software design, and

◦to define a set of requirements that can be validated once the software is built.

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Data ModelingData ModelingAnalysis Modeling

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Data ModelingData ModelingData modeling answers a set of

specific questions that are relevant to any data processing application. ◦What are the primary data objects to be

processed by the system?◦What is the composition of each data

object and what attributes describe the object?

◦Where do the objects currently reside?◦What are the relationships between each

object and other objects? ◦What are the relationships between the

objects and the processes that transform them?

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Data Objects, Data Objects, Attributes, And Attributes, And RelationshipsRelationships

Data Modeling

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Data Objects, Attributes, And Data Objects, Attributes, And RelationshipsRelationshipsData Objects

◦A data object is a representation of almost any composite information that must be understood by software.

◦A data object can be an external entity, a thing, an occurrence or event, a role, an organizational unit, a place, or a structure.

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Data ObjectsData ObjectsData Objects

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Data Objects, Attributes, And Data Objects, Attributes, And RelationshipsRelationshipsAttributes

◦Attributes define the properties of a data object and take on one of three different characteristics. They can be used to

name an instance of the data object,

describe the instance, or

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AttributesAttributesAttributes

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Data Objects, Attributes, And Data Objects, Attributes, And RelationshipsRelationshipsRelationships

◦Data objects are connected to one another in different ways.

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RelationshipsRelationshipsRelationships

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Entity Relationship Entity Relationship DiagramDiagram

Data Modeling

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Entity Relationship Entity Relationship DiagramDiagramEntity Relationship Diagram is

the representation of data objects between their relationships.

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Entity Relationship Diagram

Expanded ERD

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Functional ModelingFunctional ModelingAnalysis Modeling

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Functional ModelingFunctional ModelingInformation is transformed as it

flows through a computer-based system. The system accepts input in a variety of forms; applies hardware, software, and human elements to transform it; and produces output in a variety of forms.

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Functional ModelingFunctional ModelingInformation flow model

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Data Flow DiagramsData Flow DiagramsFunctional Modeling

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Data Flow DiagramsData Flow DiagramsAs information moves through

software, it is modified by a series of transformations.

A data flow diagram is a graphical representation that depicts information flow and the transforms that are applied as data move from input to output.

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Data Flow DiagramData Flow Diagram

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Extensions for Real-Extensions for Real-Time SystemsTime Systems

Functional Modeling

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Extensions for Real-Time Extensions for Real-Time SystemsSystemsMany software applications are time

dependent and process as much or more control-oriented information as data.

A real-time system must interact with the real world in a time frame dictated by the real world. Aircraft avionics, manufacturing process control, consumer products, and industrial instrumentation are but a few of hundreds of real-time software applications.

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Behavioral ModelingBehavioral ModelingAnalysis Modeling

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Behavioral ModelingBehavioral ModelingBehavioral modeling is an

operational principle for all requirements analysis methods.

It also reproduces the required behavior of the original analyzed system, such as there is a one-to-one correspondence between the behavior of the original system and the simulated system

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Behavioral ModelingBehavioral Modeling

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Structured Analysis Structured Analysis MechanicsMechanics

Analysis Modeling

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Entity Relationship Entity Relationship DiagramDiagram

Structured Analysis Mechanics

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Entity Relationship Entity Relationship DiagramDiagram1. During requirements elicitation,

customers are asked to list the “things” that the application or business process addresses. These “things” evolve into a list of input and output data objects as well as external entities that produce or consume information.

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Entity Relationship Entity Relationship DiagramDiagram2. Taking the objects one at a time, the

analyst and customer define whether or not a connection (unnamed at this stage) exists between the data object and other objects.

3. Wherever a connection exists, the analyst and the customer create one or more object/relationship pairs.

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Entity Relationship Entity Relationship DiagramDiagram4. For each object/relationship pair,

cardinality and modality are explored.

5. Steps 2 through 4 are continued iteratively until all object/relationships have been defined. It is common to discover omissions as this process continues. New objects and relationships will invariably be added as the number of iterations grows.

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Entity Relationship Entity Relationship DiagramDiagram6. The attributes of each entity are

defined.

7. An entity relationship diagram is formalized and reviewed.

8. Steps 1 through 7 are repeated until data modeling is complete.

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Entity Relationship Entity Relationship DiagramDiagram• Connections

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Entity Relationship Entity Relationship DiagramDiagram• Developing Relationships

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Data Flow ModelData Flow ModelStructured Analysis Mechanics

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Data Flow ModelData Flow ModelThe level 0 data flow diagram should

depict the software/system as a single bubble;

Primary input and output should be carefully noted;

Refinement should begin by isolating candidate processes, data objects, and stores to be represented at the next level;

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Data Flow ModelData Flow ModelAll arrows and bubbles should be

labeled with meaningful names;

Information flow continuity must be maintained from level to level, and

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Data Flow ModelData Flow ModelOne bubble at a time should be

refined. There is a natural tendency to overcomplicate the data flow diagram. This occurs when the analyst attempts to show too much detail too early or represents procedural aspects of the software in lieu of information flow.

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Data Flow ModelData Flow ModelLevel 0

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Data Flow ModelData Flow ModelLevel 1

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Data Flow ModelData Flow ModelLevel 1

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Grammatical ParseGrammatical ParseStructured Analysis Mechanics

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Data Flow ModelData Flow ModelLevel 1

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Data Flow ModelData Flow ModelLevel 2 – Monitor Sensors

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Control Flow ModelControl Flow ModelStructured Analysis Mechanics

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Control Flow ModelControl Flow ModelList all sensors that are "read" by

the software.

List all interrupt conditions.

List all "switches" that are actuated by an operator.

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Control Flow ModelControl Flow ModelList all data conditions.

Recalling the noun/verb parse that was applied to the processing narrative, review all "control items" as possible CSPEC inputs/outputs.

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Control Flow ModelControl Flow ModelDescribe the behavior of a

system by identifying its states; identify how each state is reached; and define the transitions between states.

Focus on possible omissions

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Control SpecificationControl SpecificationStructured Analysis Mechanics

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Control SpecificationControl SpecificationThe control specification (CSPEC)

represents the behavior of the system in two different ways.

The CSPEC contains a state transition diagram that is a sequential specification of behavior. It can also contain a program activation table—a combinatorial specification of behavior.

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Data DictionaryData DictionaryAnalysis Modeling

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Data DictionaryData DictionaryThe data dictionary is an

organized listing of all data elements that are pertinent to the system, with precise, rigorous definitions so that both user and system analyst will have a common understanding of inputs, outputs, components of stores and [even] intermediate calculations.

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Data DictionaryData DictionaryName

◦the primary name of the data or control item, the data store or an external entity.

Alias

◦other names used for the first entry.

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Data DictionaryData DictionaryWhere-used/how-used

◦a listing of the processes that use the data or control item and how it is used.

Content description

◦a notation for representing content.

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Data DictionaryData DictionarySupplementary information

◦other information about data types, preset values (if known), restrictions or limitations, and so forth.

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Data DictionaryData Dictionary

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