Unit3 Analysis and Design
An extensive amount of information is required to properly define the system's functional and nonfunctional requirements. Techniques for documenting the functional requirements by creating models is part of the analysis activity DEFINE FUNCTIONAL REQUIREMENTS, although analysis activities are actually done in parallel and in each iteration of the project. All new approaches to system development begin the requirements modeling process with the concept of a use case, an activity the system performs, usually in response to a request by a user. Two techniques recommended for identifying use cases: the user goal technique and the event decomposition technique. CRUD is also often used to validate and enhance the list of use cases. The USER GOAL TECHNIQUE is to ask users to describe their goals for using the new or updated system. First thing the analyst does is identify all the users and conduct a structured interview with each user. The analyst would guide the user to identify specific ways that a computer system can help the user to perform the assigned tasks. the objective is to identify how a system can improve the user's performance and productivity.SUBSIDIARY GOALS might include streamlining tasks the user currently performs or enabling the user to perform new tasks that are not possible or practical with the current system. The analyst documents these as use cases as they are uncovered. often the user requires guidance from the analyst to think outside the box about the the ways they currently approach their jobs. Focus groups might be formed to uncover the wants and needs of potential customers. THE STEPS FOR IDENTIFYING USE CASES:
1. IDENTIFY ALL THE POTENTIAL USERS FOR THE NEW SYSTEM.
2. CLASSIFY THE POTENTIAL USERS IN TERMS OF THEIR FUNCTIONAL ROLE(SHIPPING, MARKETING, SALES)
3. FURTHER CLASSIFY POTENTIAL USERS BY ORGANIZATIONAL LEVEL (OPERATIONAL, MANAGEMENT, EXECUTIVE)
4. FOR EACH TYPE OF USER, INTERVIEW THEM TO FIND A LIST OF SPECIFIC GOALS THEY WILL HAVE WHEN USING THE NEW SYSTEM. START WITH GOALS THEY CURRENTLY HAVE AND THEN GET THEM TO IMAGINE INNOVATIVE FUNCTIONS THEY THINK WOULD ADD VALUE. ENCOURAGE THEM TO STATE EACH GOAL IN THE IMPERATIVE VERB-NOUN FORM SUCH AS ADD CUSTOMER, UPDATE ORDER, AND PRODUCE MONTH END REPORT.
5. CREATE A LIST OF PRELIMINARY USE CASES ORGANIZED BY TYPE OF USER.
6. LOOK FOR DUPLICATES WITH SIMILAR USE CASE NAMES AND RESOLVE INCONSISTENCIES.
7. IDENTIFY WHERE DIFFERENT TYPES OF USERS NEED THE SAME USE CASES.
8. REVIEW THE COMPLETED LIST WITH EACH TYPE OF USER AND THEN WITH INTERESTED STAKEHOLDERS.
The most comprehensive technique for identifying use cases is the EVENT DECOMPOSITION TECHNIQUE this technique begins by identifying all the business events that will cause the information system to respond, and each event leads to a use case. ACTOR AN EXTERNAL AGENT; A PERSON OR GROUP THAT INTERACTS WITH THE SYSTEM BY SUPPLYING OR RECEIVING DATA.TO IDENTIFY THE KEY EXTERNAL EVENTS, THE ANALYST FIRST TRIES TO IDENTIFY ALL THE EXTERNAL AGENTS THAT MIGHT WANT SOMETHING FROM THE SYSTEM. A CLASSIC EXAMPLE IS A CUSTOMER.
AUTOMATION BOUNDARY: DEFINES THE BORDER BETWEEN THE COMPUTERIZED PROTIO OF THE APPLICATION AND THE PEOPLE OPERATING THE APPLICATION. IT IS SHOWN AS A RECTANGLE CONTAINING THE USE CASE/ THE BOUNDARY BETWEEN THE COMPUTERIZED PORTION OF THE APPLICATION AD THE USERS WHO OPERATE THE APPLICATION BUT ARE PART OF THE TOTAL SYSTEM.
ACTOR AN EXTERNAL AGENT; A PERSON OR GROUP THAT INTERACTS WITH THE SYSTEM BY SUPPLYING OR RECEIVING DATA.TO IDENTIFY THE KEY EXTERNAL EVENTS, THE ANALYST FIRST TRIES TO IDENTIFY ALL THE EXTERNAL AGENTS THAT MIGHT WANT SOMETHING FROM THE SYSTEM. A CLASSIC EXAMPLE IS A CUSTOMER.
AUTOMATION BOUNDARY: DEFINES THE BORDER BETWEEN THE COMPUTERIZED PROTIO OF THE APPLICATION AND THE PEOPLE OPERATING THE APPLICATION. IT IS SHOWN AS A RECTANGLE CONTAINING THE USE CASE/ THE BOUNDARY BETWEEN THE COMPUTERIZED PORTION OF THE APPLICATION AD THE USERS WHO OPERATE THE APPLICATION BUT ARE PART OF THE TOTAL SYSTEM.
BRIEF USE CASE DESCRIPTIONS: It is important to recognize that this list of use cases will continue to evolve as the project progresses. Additional use cases will be added some might be eliminated, and some might be combined. It is helpful to immediately describe some of the details of each use case, preferable in one sentence. this brief description is usually expanded to record more to the details when the developers are designing and implementing the use case. In short, often a one-sentence description that provides a quick overview of a use case.
CRUD TECHNIQUE: An important technique used to validate and refine use cases. The acronym for Create, Read or Report, Update, and Delete, THe analyst starts by looking at the types of data stored by the system which are modeled as data entities or domain classes.
ELEMENTARY BUSINESS PROCESSES (EBPs): THE MOST FUNDAMENTAL TASKS IN BUSINESS PROCESSES-An EBP is a task that is performed by one person in one place in response to a business event, adds measurable business value and leaves the system and its data in a stable and consistent state.
EVENT: An event occurs at a specific time and place, can be described and should be remembered by the system. Events drive or trigger all processing that a system does, so listing events and analyzing them makes sense when you need to define system requirements by identifying use cases.
EVENT DECOMPOSITION TECHNIQUE: THE MOST COMPREHENSIVE TECHNIQUE FOR IDENTIFYING USE CASES IS THE EVENT DECOMPOSITION TECHNIQUE. it begins by identifying all the business events that will cause the information system to respond and each event leads to a use case.
EXTERNAL EVENT: An event that occurs outside the system- usually initiated by an external agent or actor. An external agent( or actor) is a person or organizational unit that supplies or receives data from the system To identify the key external events, the analyst first tries to identify all the external agents that might want something from the system .
<<INCLUDES>> RELATIONSHIP: A relationship between use cases in which one use case is stereotypically included within the other use case
PERFECT TECHNOLOGY ASSUMPTION: States that events should be included during analysis only if the system would be required to respond under perfect conditions. By pretending that technology is perfect, analysts can eliminate events like" time to back up the database" because they can assume that the disk will never crash. Again during design the project team adds these controls because technology is obviously not perfect.
STATE EVENT: An event that occurs when something happens inside the system that triggers the need for processing. State events are also called Internal events.
SYSTEM CONTROLS: Are checks or safety procedures put in place to protect the integrity of the system.
TEMPORAL EVENT: An event that occurs as a result of reaching a point in time.
USE CASE : An activity that the system performs, usually in response to a request by a user.
USE CASE DIAGRAM: THe UML model used to graphically show use cases and their relationships to actors.
USER GOAL TECHNIQUE: Is to ask users to describe their goals for using the new or updated system. The analyst first identifies all the users and then conducts a structured interview with each user.
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