Chapter 12 Analysis Modeling 1 Analysis Modeling Where

Chapter 12 Analysis Modeling 1

Analysis Modeling: Where to Begin? Use the statement of scope and other SRS documents already created to guide you to building an analysis model. The analysis model will include acquired from: the working document A set of use-cases Other items the statement of scope must be “parsed” to extract data, function and behavioral domain information 2

Statement of Scope a relatively brief description of the system to be built indicates data that are input and output and basic functionality indicates conditional processing (at a high level) implies certain constraints and limitations 3

Identifying Object and Operations Noun/Verb Approach define “objects” by underlining all nouns in the written statement of scope producers/consumers of data places where data are stored “composite” data items define “operations” by double underlining all active verbs processes relevant to the application data transformations consider other “services” that will be required by the objects 4

Identifying Object and Operations Discovery Approach define all “potential objects” by thinking about the system. Consider everything. Add attributes identifying those potential objects which are duplicates, attributes themselves, operations, services. Add operations again identifying those potential objects which are duplicates, attributes, operations, and services. 5

Identifying Object and Operations Data Approach define all data entities and consider them as the potential objects of the system. Add attributes identifying those potential objects which are duplicates, attributes themselves, operations, services and adding any new objects needed to support attributes. Add operations again identifying those potential objects which are duplicates, attributes, operations, and services and adding any new objects needed to support operations. 6

Video Rental Example A video store offers rental of videos to members. To become a member you have to have a drivers license and a credit card. You may rent up to 3 videos. Corporate keeps up with trends and orders the tapes for rental. Members check out and return videos due in one day. Overdue fees of 1 dollar a day is charged for late videos. Upon rental a rental slip is made for customers which contains name, addr, city, and iterations of movies with tape id, movie id, title, length, etc. 7

Video Rental System Use the noun approach - Grady Booch Use discovery approach – Linda Northrup Use the data approach – Steven Mellor, Sally Schaler Use the responsibility driven design approach – Rebecca Wirth Brock Use one of above and Analysis Patterns Approach – Joe Yoeder 8

Video Rental System Remember these techniques identify the domain (conceptual) classes, not design classes, not programming classes, and not implementation classes. 9

Video Rental System noun/verb A video store offers rental of videos to members. To become a member you have to have a drivers license and a credit card. You may rent up to 3 videos. Corporate keeps up with trends and orders the tapes for rental. Members check out and return videos due in one day. Overdue fees of 1 dollar a day is charged for late videos. Upon rental a rental slip is made for customers which contains name, addr, city, and iterations of movies with tape id, movie id, title, length, etc. 10

Video Rental System noun/verb A video store offers rental of videos to members. To become a member you have to have a drivers license and a credit card. You may rent up to 3 videos. Corporate keeps up with trends and orders the tapes for rental. Members check out and return videos due in one day. Overdue fees of 1 dollar a day is charged for late videos. Upon rental a rental slip is made for customers which contains name, addr, city, and iterations of movies with tape id, movie id, title, length, etc. 11

Video Rental System noun/verb NOUNS Store Video Member License Card Corporate Trends Tapes Slip Customers Name Addr City Iterations Tape Movie id Title length VERBS Offers Becomes Rents Orders Checkout Return Charged Made contains 12

Video Rental System noun/verb Lay the nouns out on a table, 3 X 5 cards, chalk board, ppt file NOUNS Store Video Member License Card Corporate Trends Tapes Slip Name Customers Addr Iterations Movie id Tape Title length 13

Video Rental System noun/verb Begin adding attributes NOUNS Store name, addr. . Video name, length Member name, addr License num, name Card num, name, Corporate Trends Tapes Slip Name Customers Addr Iterations Movie id Tape name, addr. . Title Id num length 14

Video Rental System noun/verb Begin clustering the potential objects - Singletons NOUNS Store name, addr. . Corporate Video name, length Trends Same as store only one instance Customers Addr name, addr. . Title Member name, addr License num, name Card num, name, Tapes Slip Name Iterations Movie id Tape Id num length 15

Video Rental System noun/verb Begin clustering the potential objects - attributes NOUNS Store Video name, addr. . name, length Corporate Trends Same as store only one instance Customers Addr name, addr. . attribute Title Member name, addr License num, name Tapes Slip Iterations Movie id Card num, name, Name attribute Id Tape num attribute length 16

Video Rental System noun/verb Begin clustering the potential objects – more attributes NOUNS Store name, addr. . Video name, length Member License attribute Card name, addr lic num, card num Trends Tapes Slip Customers name, addr. . Iterations Movie id attribute Id Addr attribute Tape ID attribute num 17

Video Rental System noun/verb Begin clustering the potential objects - duplicates / descriptors NOUNS Store name, addr. . Video name, length Member name, addr lic num, card num Trends Tapes Slip name, addr. . = to Customers member descriptor Iterations` 18

Video Rental System noun/verb Begin clustering the potential objects - I/O NOUNS Store name, addr. . Video Member name, length name, addr lic num, card num Trends Tapes tape id, Slip name, addr. . I/O 19

Video Rental System noun/verb So how did we do this clustering 1. Identified all potential domain (conceptual classes) using the noun approach --discovery, data methods, or responsibility driven also work. 2. Identified potential attributes and perhaps operations of the potential classes. 20

Video Rental System noun/verb 4. Eliminated some potential classes by clustering • Input/Outputs (never domain classes) • Singletons (rarely classes) • Potential objects that turned out to be attributes • Potential objects that turned out to be behaviors • Duplicates • Items that only described other things ( no attributes or methods) 5. Constructed the Class Diagram and the network helped to cluster even more. 6. Identify M: M and resolved 21

Video Rental System noun/verb Begin clustering the potential objects by their attributes and methods Store Video Trends VERBS Member Tape Now lets see if we can model this……. Now add cardinality, names of relationships…resolve M: M… then add attributes and methods Offers Becomes Rents Orders Checkout Return Charged Made contains 22

Data Modeling and Entity Relationship (E-R) Diagramming 23

Why Data Modeling? examines data objects independently of processing focuses attention on the data domain creates a model at the customer’s level of abstraction indicates how data objects relate to one another 24

What is a Data Object? Object—something that is described by a set of attributes (data items) and that will be manipulated within the software (system) each instance of an object (e. g. , a book) can be identified uniquely (e. g. , ISBN #) each plays a necessary role in the system i. e. , the system could not function without access to instances of the object each is described by attributes that are themselves data items 25

Typical Objects external entities (printer, user, sensor) things (e. g, reports, displays, signals) occurrences or events (e. g. , interrupt, alarm) roles (e. g. , manager, engineer, salesperson) (e. g. , division, team) organizational units places (e. g. , manufacturing floor) structures (e. g. , employee record) 26

Data Objects and Attributes A data object contains a set of attributes that act as an aspect, quality, characteristic, or descriptor of the object: automobile attributes: make model body type price options code 27

What is a Relationship? relationship —indicates “connectedness”; a "fact" that must be "remembered" by the system and cannot or is not computed or derived mechanically several instances of a relationship can exist objects can be related in many different ways 28

ERD Notation One common form: object 1 (0, m) relationship (1, 1) object 2 attribute Another common form: object 1 relationship (0, m) (1, 1) object 2 29

Building an ERD Level 1—model all data objects (entities) and their “connections” to one another Level 2—model all entities and relationships Level 3—model all entities, relationships, and the attributes that provide further depth 30

The ERD: An Example Customer (1, 1) places (1, m) request for service (1, 1) standard task table (1, 1) work selected from (1, w) tasks materials generates (1, n) (1, w) (1, i) work order (1, 1) consists of lists 31

Creating a Flow Model 32

The Flow Model Every computer-based system is an information transform. . input computer based system output 33

The Flow Model Every computer-based system is an information transform. . input computer based system output 34

Flow Modeling Notation external entity process data flow data store 35

External Entity A producer or consumer of data Examples: a person, a device, a sensor Another example: computer-based system Data must always originate somewhere and must always be sent to something 36

b Process A data transformer (changes input to output) Examples: compute taxes, determine area, format report, display graph Data must always be processed in some way to achieve system function 37

Data Flow Data flows through a system, beginning as input and be transformed into output. base height compute triangle area 38

Data Stores Data is often stored for later use. sensor # report required sensor #, type, location, age look-up sensor data sensor number type, location, age sensor data 39

Data Flow Diagramming: Guidelines icons must be labeled with meaningful names DFD evolves through a number of levels of detail always begin with a context level diagram (also called level 0) always show external entities at level 0 always label data flow arrows do not represent procedural logic 40

Constructing a DFD—I review ERD to isolate data objects and grammatical parse to determine “operations) determine external entities (producers and consumers of data create a level 0 DFD 41

Level 0 DFD Example user processing request digital video processor requested video signal monitor video NTSC source video signal 42

Constructing a DFD—II write a narrative describing the transform parse to determine next level transforms “balance” to maintain data flow continuity develop a level 1 DFD use a 1: 5 (approx. ) expansion ratio 43

The Data Flow Hierarchy x a p 1 a c d level 1 b P p 2 level 0 f p 4 p 3 y e g 5 b 44

Flow Modeling Notes each bubble is refined until it does just one thing the expansion ratio decreases as the number of levels increase most systems require between 3 and 7 levels for an adequate flow model a single data flow item (arrow) may be expanded as levels increase (data dictionary provides information) 45

DFDs: A Look Ahead analysis model Maps into design model 46

Creating a Use Case Model 47

The Use Case Model Every computer-based system is a series of actions, subsystems that interact with outside actors (external entities). use case 48

Use Case Notation actor relationship (usually trigger) use case 49

Actor A Examples: a person, a device, a sensor Another example: computer-based system Something must trigger the action in the use case. 50

Use Case (Process) A process triggered by a user Examples: compute taxes, determine area, Enter student data, These functions must be performed. 51

Connection The actors trigger the process. use case 52

Use Case Guidelines use cases like processes vary in granularity. show a good way to begin defining system scenarios. offer an abstraction which can have a test plan begin the traceability of the system has extensions <<extends>> for extending the functionality of a use case <<uses>> for using when one use case uses another use case <<include>> for inner use of a use case inside another <<calls> for invocation of other use cases. 53

Constructing a Use Case Review the needed processes triggered by users. determine the actors involved. create the first level of use cases Define any extensions. 54

High Level Use Cases System Video Rental System Use Case Order new videos Corporate Rent video Return video Customer Actor 55

Constructing Use Cases write a narrative describing the use case Define the classes (if known) that participate in that use case Define the pre and post conditions of the use case. 56

Use Case Diagrams: A Look Ahead Rent video use Customer case model Maps into sequence design model Customer validate. Custom er() rent. Cassette(CI D) Rental Cassette check. If. Rentable(CID ) 57

Behavioral Modeling and Process Specification 58

Behavioral Modeling events Outside world behavior Application 59

The States of a System state—a set of observable circumstances that characterizes the behavior of a system at a given time state transition—the movement from one state to another event—an occurrence that causes the system to exhibit some predictable form of behavior action—process that occurs as a consequence of making a transition 60

Behavioral Modeling make a list of the different states of a system (How does the system behave? ) indicate how the system makes a transition from one state to another (How does the system change state? ) indicate event indicate action draw a state transition diagram 61

State Transition Diagram Notation state event causing transition action that occurs new state 62

State Transition Diagram full and start invoke manage-copying reading operator commands full invoke read-op-input copies done invoke read-op-input making copies reloading paper empty invoke reload paper jammed invoke problem-diagnosis problem state not jammed invoke read-op-input 63

Writing the Software Specification Everyone knew exactly what had to be done until someone wrote it down! 64