Chpt8:Two perspectives
on data modeling:Top-down approach for a data model is derived from an
clear understanding of the business processes.Bottom-up approach for a data
model is derived by reviewing specifications and business documents.gathering
information: What characteristics describe each subject/object?Attributes and
secondary keys.How do you use the data?Via security controls and user access
privileges.Over what period of time are you interested in the data?Cardinality and
time dimensionsAre all instances of each object the same?Supertypes, subtypes,
and aggregationsWhat events occur that imply associations between
objects?Relationships and cardinalities Are there special circumstances that
affect the way events are handled? Integrity rules, minimum and maximum
cardinalities, time dimensions. E-R model is describing a breakdown of what you
would see have a data store of the DFD.There are
various typeidentifiers;DERIVED, MULTIVALUED,COMPOSITE.3-An identifier uniquely identifies an
instance of an entity;Only one instance of the entity type may have a specific
identifier value.An entity type definition:Includes a
statement of what the unique
characteristic(s) is (are) for each instance (std id).Makes clear what entity
instances are included and not included in the entity type.Often includes a
description of when an instance of the entity type is created or deleted.Attribute: a named property or characteristic of an entity that
is of interest to the organizationNaming an attribute: i.e. Vehicle_ID Place
its name inside the rectangle for the
associated entity in the E-R diagram.An attribute name is a noun and should be
unique.To make an attribute name unique and for clarity, each attribute name
should follow a standard format.Similar attributes of different entity types
should use similar but distinguishing names. Attri i should indicate:If a value for the attribute
is required or optional.Candidate key: an attribute (or combination of
attributes) that uniquely identifies each instance of an entity typeIdentifier:
is a candidate key that has been selected as the unique, identifying
characteristic for an entity type .Selection rules for an identifier:Choose a
candidate key that will not change .its value never be null.Avoid using intelligent keys.Consider to take single value the surrogate
keys for large composit keys.Relationship: an association between the
instances of one or more entity types that is of interest to the organization
Degree: the number of entity types that participate in a relationship.
Cardinality: the number of instances of entity B that can (or must) be
associated with each instance of entity A. Minimum Cardinality The
minimum number of instances of entity B that may be associated with each
instance of entity A Maximum Cardinality The maximum number of instances of
entity B that may be associated with each instance of entity A.An associative entity is kind of a combination
of entity and relationship.Associative Entity: an entity type that
associates the instances of one or more entity types and contains attributes
that are strange to the relationship between those entity instancesSometimes
called a gerund .The data modeler chooses to model this relationship as an
entity type.Subtype: a subgrouping of the entities in an entity type Is
meaningful to the organization.Shares common attributes or relationships
distinct from other subgroupings Supertype: a generic entity type that
has a relationship with one or more subtypes.Business rules: specifications that preserve
the integrity of the logical data model.Business rules: specifications that preserve the integrity of the
logical data modelCaptured during requirements determination
Stored in CASE repository as they are documented.Four basic types of business rules are:Entity integrity and referential
integrity are both expressed in the E-R model. But domains and triggers are
not.Entity integrit): unique, non-null identifiers Referential integrity
constraints): rules governing relationships between entity types ..Domains:
constraints on valid values for attributes Triggering operations: other
business rules that protect the validity of attribute values..Domain: the set of all data types and values that an attribute
can assume.advantages of Domain:Verify that the values
for an attribute are valid/Ensure that various data manipulation operations are
logical/Help conserve effort in describing attribute characteristics.Trigger: an assertion or rule that manages the validity of data
operations such as insert, update and delete.Triggers includes the following components: User rule: statement of the
business rule to be enforced by the trigger Event: data manipulation
operation that initiates the operation/Entity Name: name of entity being
accessed or modified/Condition: condition that causes the operation to be
triggered/Action: action taken when the operation is triggered.Packaged data models provide generic models that can be customized for a
particular organization’s business rules./Universal data models are templates
for one or more core subject areas such as:customers, products, accounts,
documents and/or core business functions such as:Purchasing, accounting,
receiving, etc.Role:Industry-specific data models are designed to
be used by organizations within specific industries.These models are based on
the premise that data model patterns for organizations are similar within a
particular industry.benefits of pack db and models:Dramatically reduced implementation times and
costs/ Provides a starting point for asking requirements questions
Higher-quality models Represent “best practice” data modeling techniques and
data model components whose quality often exceeds that which can be achieved by
internal development teams, given typical organizational pressures.Chpt13:Systm Implementation: Purpose:To
convert final physical system specifications into working and reliable
software/To document work that has been done/To provide help for current and
future users. Six major activities:Coding/Testing/ Installation /Documentation/Training/Support.
Coding:Physical design specifications are turned into working computer
code.Testing:Tests are performed using various strategies.Testing is performed
in parallel with coding.Installation:The current system is replaced by a new system.documenting/training/supportingusers:
Two audiences for final documentation: Information systems personnel who will
maintain the system throughout its productive life.People who will use the
system as part of their daily lives.User Training:Application-specific.General
for operating system and off-the-shelf software.softwareapplicationtesting:
A master test plan is developed during the analysis phase.During the design
phase, unit, system and integration test plans are developed.The actual testing
is done during implementation.Written test plans provide improved communication
among all parties involved in testing.7diffrnttests: Static or
dynamic techniques.Static testing means that the code being tested is not
executed.Dynamic testing involves execution of the code.Test is automated or
manualAutomated means computer conducts the test.Manual means that people
complete the test. Inspection: a testing technique in which participants
examine program code for predictable language-specific errors.Walkthrough: a
peer group review of any product created during the systems development
process, including code.Desk checking: a testing technique in which the program
code is sequentially executed manually by the reviewer. Unit testing:
each module is tested alone in an attempt to discover any errors in its
code.Integration testing: the process of bringing together all of the modules
that a program comprises for testing purposes.Modules are typically integrated
in a top-down incremental fashion. System testing: the bringing together
of all of the programs that a system comprises for testing purposes.Programs
are typically integrated in a top-down, incremental fashion. Stub testing:
a technique used in testing modules, especially where modules are written and tested
in a top-down fashion, where a few lines of code are used to substitute for
subordinate modules.The purpose of testing is to confirm that the system
satisfies the requirements.Testing must be planned.Test case is a
specific scenario of transactions, queries or navigation paths. Test cases
represent either:typical system use/Critical system use, or Abnormal system
use. Test cases and results should be thoroughly documented so they can be
repeated for each revision of an application. Testingharness:Automated testing
environment,Reviews code for:Errors/Standards violations/Other design flaws.Expand
the scope of the tests beyond the current development platform. Combine:
Coding and testing often go together.Big companies have dedicated test
staff.With eXtreme programming (XP) a common technique is
refactoring.Refactoring = making a program simpler after adding a new
feature.Acceptance testing: the process whereby actual users test a
completed information system, the end result of which is the users’ acceptance
of it. Alpha testing: user testing of a completed information system using
simulated data/Beta testing: user testing of a completed information system
using real data in the real user environment. Types of Alpha Test:Recovery
testing:forces software (or environment) to fail in order to verify that
recovery is properly performedSecurity testing:verifies that protection
mechanisms built into the system will protect it from improper
penetrationStress testing:tries to break the systemPerformance testing: determines
how the system performs on the range of possible environments in which it may
be used. Installation: the organizational process of changing over from
the current information system to a new one.Four installation strategies:Direct
Installation/Parallel Installation/Single-location installation/Phased
Installation. Direct installation: changing over from the old system to a new
one by turning off the old system when the new system is turned on. Parallel
installation: running the old information system and the new one at the same
time until management decides the old system can be turned off. Single-location
installation: trying out an information system at one site and using the
experience to decide if and how the new system should be deployed throughout
the organization(aka location or pilot installation).planinginstallation:
Considerationn/Data conversion/Error correction/Loading from current
system/Planned system shutdown/Business cycle of organization. System
documentation: detailed information about a system’s design specifications,
its internal workings, and its functionalitiy.User documentation:
written or other visual information about an application system, how it works,
and how to use it. Support: providing ongoing educational and problem-solving
assistance to information system users. Potential training topics/Use of
the system/General computer concepts/Information system concepts/Organizational
concepts/System management/System installation. Help desk: a
single point of contact for all user inquiries and problems about a particular
information system or for all users in a particular department. Requires
Technical skills: extensive knowledge about how to use the system and typical
problems that can be encountered/People skills: good listening and
communication, dealing with complaints and frustrations.chpt10 Common
Types of Reports:Scheduled:contains routine info & it is produced at
predefined time intervals for routine information needs.Key-indicator:contains
key data & provides summary of critical information on regular
basis.Exception:shows data outside of normal operating
ranges,Drill-down:provides details behind summary of key-indicator or exception
reports.Ad-hoc:responds to unplanned requests for non-routine information
needs. Wireframe İs a simple design to show the placement of information
elements on a screen and the space needed for each element, Prototyping.Initial
prototype is designed from requirements.Users assess prototype design and
either accept the design or request changes.If changes are requested, the
construction-evaluation-refinement cycle is repeated until the design is
accepted. A coding sheet is an “old” tool for designing forms and
reports,Usually related with text-based forms and reports for mainframe
applications.Visual Basic and other development tools (sketch 3, mockflow,
tools etc..) provide computer-aided GUI form and report generation. Design
specifications have three sections:Narrative overview :describes users, tasks,
system, and environmental factors .Sample design: is the image of the form
(from coding sheet or form building development tool).Testing and usability
assessment: measuring test/ usability results (consistency, sufficiency,
accuracy, etc.) General Guidelines :Meaningful titles :use clear, specific,
version information, and current dateMeaningful information: include only
necessary information, with no need to modify. Balanced layout: use adequate
spacing, margins, and clear labels.Easy navigation system :show how to move
forward and backward, and where you are currently. highlighting information is
to point out things that need special attention. Notify users of errors in data
entry or processing.Provide warnings regarding possible problems.Draw attention
to keywords, commands, high-priority messages, unusual data values. Benefits —
Color:Soothes or strikes the eye .Accents an uninteresting display.Facilitates
fine differences in complex displays ..Emphasizes the logical organization of
information.Draws attention to warnings.Evokes more emotional reactions.
Problems Color pairings may cause problems for some users.Resolution may
degrade with different displays.Color fidelity/harmony may degrade on different
displays .Printing or conversion to other media may not easily
translate.displayingtext Case: display in mixed upper and lower case, use
conventional punctuation.Spacing: use double spacing if possible, otherwise
blank lines between paragraphs.Justification: left justify text, ragged right
margins.Hyphenation: don’t hyphenate words between lines.Abbreviations: use
only when widely understood and if it too shorter than full text. Labels.All
columns and rows should have meaningful labels.Labels should be separated from
other information by using highlighting.Redisplay labels when the data extend
beyond a single screen or page. Formatting columns, rows and text:Sort in a
meaningful order.Place a blank line between every five rows in long
columns.Similar information displayed in multiple columns should be sorted vertically.Columns
should have at least two spaces between them.Allow white space on printed
reports for user to write notes.Use a single typeface, except for emphasis.Use
same family of typefaces within and across displays and reports.Avoid
excessively fancy fonts (like this..) Formatting numeric, textual and
alphanumeric data:Right justify numeric data and align columns by decimal
points or other delimiter.Left justify textual data. Use short line length, usually 30 to 40
characters per line.Break long sequences of alphanumeric data into small groups
of three to four characters each. Use TABLES for reading individual data
values.Use GRAPHS for:Providing quick summary./Displaying trends over
time.Comparing points and patterns of variables.Forecasting activity.Simple
reporting of massive quantities of information. Usability: is an overall
evaluation of how a system performs in supporting a particular user for a
particular task.Three characteristics of usability:Speed /Accuracy
/Satisfaction .successfactor Consistency :of terminology, formatting, titles,
navigation, response time/Organization:good text/data alignment for efficient
navigation and entry/Ease:self-explanatory
and brief outputs and labels/Format :appropriate display of data and
symbols/Flexibility :maximize user options for data input according to user
preference. Characteristics for consideration:User: experience, skills,
motivation, education, personality/Task: time pressure, cost of errors, work
durations/System: platform /Environment: social and physical issues.measures:
Learnability /Efficiency /Error rate /Memorability /Satisfaction and aesthetic.
Lightweight Graphics: the use of small, simple images to allow a Web page to
more quickly be displayed/Quick image download/Quick feedback from the Web site
will help to keep customers at the PVF WebStore longer.Chpt11: Interface
design : focuses on how information is provided to and captured from
users.Dialogues: analogous to a conversation between two people Designing
Interfaces and Dialogues is an User-focused activity.Prototyping methodology of
iteratively:Collecting information/Constructing a prototype/Assessing
usability:Usability refers to how easy, informative, and enjoyable is the
user’s experience with the system.Making refinements:Must answer the who, what,
when, where, and how questions. The Design Specification of Interfaces and
Dialogues involves those steps :Narrative overview /Sample design/Testing and
usability assessment/Dialogue sequence//Dialogue sequence:the ways a user can
move from one display to another. Interface: is a method by which users
interact with an information system/All human-computer interfaces must:/ have
an interaction style, and use some hardware device(s) for supporting this
interaction.mthods: Command line /Menu/Form/Object-based/Natural language.
Command language interaction: is a human-computer interaction method whereby
users enter explicit statements into a system to invoke operations. Menu
interaction:is a human-computer interaction method in which a list of system
options is provided and a specific command is invoked by user selection of a
menu option.Pop-up menu: is a menu-positioning method that places a menu near
the current cursor position. Drop-down menu is a menu-positioning method that
places the access point of the menu near the top line of the display.When
accessed, menus open by dropping down onto the display.Visual editing tools
help designers construct menus. Guidelines for Menu Design Wording :meaningful
titles, clear command verbs, mixed upper/lower case Organization :consistent or
steady organizing principle Length: all choices of menu fit within screen
length Selection :consistent, clear and easy selection method/Highlighting
:only for selected options or unavailable options. Form interaction: is a highly
intuitive human-computer interaction method whereby data fields are formatted
in a manner similar to paper-based forms Allows users to fill in the blanks
when working with a system.. Object-based interaction: a human-computer
interaction method in which symbols are used to represent commands or
functions.Icons: graphical pictures that represent specific functions within a
system.Use little screen space and are easily understood by users. Natural
language interaction: is a human-computer interaction method whereby inputs to
and outputs from a computer-based application are in a conventional spoken
language such as English. Hardware option systm interaction:
Keyboard/Mouse/Joystick/Trackball/ Touch screen/Light Pen/Graphics
Tablet/Voice.usuability problem: Visual Blocking:Extent to which device blocks
display when using/User Fatigue:Potential for fatigue over long use/Movement
Scaling:Extent to which device movement translates to equivalent screen
movement /Durability:Lack of durability or need for maintenance (e.g.,
cleaning) over extended use. Adequate Feedback:Extent to which device provides
adequate feedback for each operation/Speed:Cursor movement speed/Pointing
Accuracy:Ability to precisely direct cursor. Forms have several general areas
in common:Header information/Sequence and time-related information /Instruction
or formatting information/Body or data details/Totals or data
summary/Authorization or signatures/Comments. Three types of system
feedback:Status information: keep user informed of what’s going on, helpful
when user has to wait for responsePrompting cues: tell user when input is
needed, and how to provide the inputError or warning messages: inform user that
something is wrong, either with data entry or system operation.usablehelp:
Simplicity :Help messages should be short and to the point.Organize:
Information in help messages should be easily absorbed by users.Show: It is
useful to explicitly show users how to perform an operation. Dialogue: the
sequence of interaction between a user and a system/Dialogue design
involves:/Designing a dialogue sequence./Building a prototype./Assessing
usability. Dialogue diagramming: a formal method for designing and representing
human-computer dialogues using box and line diagrams. Top:contains a unique display
reference number used by other displays for referencing it/Middle:contains the
name or description of the display/Bottom:contains display reference numbers
that can be accessed from the current display. Cookie crumbs: the technique of
placing “tabs” on a Web page that show a user where he or she is on a site and
where he or she has been/Allow users to navigate to a point previously visited
and will assure they are not lost/Clearly show users where they have been and
how far they have gone from home.
