Requirements Gathering CSCI 4800/6800 Feb. 25, 2003

Goals What does the client want/need? (goal: go from vague to specific) Representation of problems with current system Representation of requirements of new system

Techniques Interviewing/questionnaires Observation Document analysis Prototyping Checklists

Types of Requirements Functional - what system must do Data - structure of system or data neccessary Usability - acceptable levels of user performance & satisfaction

Functional Requirements Both human & system Dataflow diagrams Data dictionaries

Data Requirements Entity-Relationship diagrams

Usability requirements Learnability Throughput Flexibility Attitude

Functional Requirements What the system does What the user does Result of analysis & collecting requirements is functional specification Dataflow diagrams Document or other representation Separate modules Organized hierarchically

Functional Requirements Databases - more persistent than dataflows An abstraction of the existing system, not a copy of the current physical process Basis for structured walkthrough - verbal description of the system based on the diagrammatic representation Other approaches: Flow charts Scenarios - good for HCI

Data Requirements Attention on structure rather than processing Elicit using Observation Document analysis Interviewing etc.

Data Requirements Entity-Relationship (ER) diagrams used with formal descriptions of data elemtents, entities, & relationships kept in a data dictionary, to describe structure & context of the data in a system Entity-Relationship (ER) diagrams Entity - aggregation of a number of data elements (attributes of the entity) Entity type - classification according to shared attributes/attribute types Relationships - association between two or more entities

Usability requirements Easy to learn & remember, Useful, Easy & pleasant to use Learnability – Time/effort to reach specified level Throughput – Tasks accomplished by experienced users – Speed of task execution – Errors made Flexibility – Extent to which system can accommodate changes Attitude

Determining usability requirements: Task analysis – (next section) – determine cognitive and other characteristics required of users by system (search strategy, prereq knowledge, cognitive loading, etc.) User analysis – – determine scope of population who will use the system – user modeling techiques may be applied here; typically use checklists Environment analysis – where system will operatre

Task Analysis determine cognitive and other characteristics required of users by system – search strategy – prereq knowledge – cognitive loading – etc.

User Analysis User analysis – – determine scope of population who will use the system – user modeling techiques may be applied here – typically use checklists

Environment Analysis where system will operate – Physical aspects – User support environment – more

Usability requirements Expressed as usability metrics – Completion time for specific tasks by specific set or type of user – Number of errors per task – Time spent using documentation

Usability metrics time to complete task % of task complete % complete per unit time success:failure ratio time spent on errors % number of errors number of commands used frequency of doc/help use time spent in help/doc favorable:unfavorable comments number of reps. of failed commands number of successful runs number of failure runs number of times interface misleads user.... & more

Components of usability Learnability – time and effort required to reach a specified level of use performance (‘ease of learning’) Throughput – tasks accomplished by experienced users – speed of task execution, number and type of errors Flexibility – extent to which system can accomodate change Attitude – do users like it?

Usability study the act of gathering usability requirements involves: – task analysis – user analysis – environment analysis

Task analysis determine characteristics, particularly cognitive characteristics, required of users by system – search strategy – pre-req knowledge – cognitive loading

User analysis determine scope of user population that will use system – intellectual ability, cognitive processing ability, previous experience, physical capabilities typically a checklist description, rather than chart or diagram as in dataflow and E-R

Environment analysis physical environment – temperature, humidity, lighting, available space social environment – quiet/loud, busy/isolated, etc. user support environment – helpful/hostile