Use Cases for a Generic Information Sharing System

1
Use Cases for a Generic Information Sharing System

• Walt Scacchi, Ph.D.
• Systems Analysis and Design
• for ECommerce and EBusiness
• GSM 271/FEMBA 271
• Fall 2001

2
Use Case Review

• A Use Case tells a story of reaching a goal,
• or a set of stories about reaching or failing.

3
Use Case Review

• A UC story captures
• a relation (activity designated by a verb/verb
  phrase)
• the role/community/actor who performs the
  activity
• normal, exceptional and error scenarios
• Scenarios are narratives that describes a
  sequence of steps, actions or other activities
• Scenarios identify objects that the actor
  manipulates through the relation
• Objects have attributes which may be manipulated
  by steps in the relation

4
A Use Case Example

• UC 4 Place an order
• (Normal Scenario)
• 1. The clerk identifies the customer, each item
  and quantity.
• 2. System accepts and queues the order.
• (Exception Scenarios)
• 1a. Low credit Clerk takes prepayment
• 2a. Low on stock Customer accepts reduced...

5
Use Case Example in detail

• Place an order -- the relation as a verb phrase
• Clerk, Customer and System are the actors
• Order (as in purchase_order) is an object
  manipulated by the clerk and system
• Order has attributes customer-identifier,
  item, quantity, credit-status, etc.

6
Format for Capturing a Use Case

• UC Identifier (a verb phrase identifying the
  relation)
• Scenarios
• (Optional) Use Case Diagram
• Items specific to the relation extracted from the
  Rich Picture
• UML has a modeling/diagramming construct called a
  Use Case Diagram, which is a more primitive
  subset of a Rich Picture.
• Search for details Use Case Diagram on the Web

7
Reusable Use Cases for an Information Sharing
SystemGlobal File Sharing System or Enterprise
Portal
8
Relations in lt! -- an ISSgt

• Create/edit upload content
• note content is an abstract object type that
  has many enumerated sub-types
• Download content
• Edit/upload content
• Upload messages/personal content

• Do Messaging
• Do Email
• Access other Web content
• Manage lt! -- an ISSgt content
• Develop Test lt! -- an ISSgt

9
Create/edit upload content

• lt! -- Authorsgt create (insert) new content or
  edit (update) existing content
• lt! -- Authorsgt can transmit the content they
  create to lt! -- Publishersgt for editupload into
  lt! -- an ISSgt, else lt! -- Authorsgt upload their
  content into lt! -- an ISSgt
• lt! -- Authorsgt/staff can only upload one type of
  content at a time into lt! -- an ISSgt
• (Exception) lt! -- an ISSgt will allow existing
  content to be copied from one content object to
  another without upload.
• lt! -- Authorsgt can only edit (update) content
  they have individually created
• (Exception) lt! -- Authorsgt may copy and paste
  content created by other lt! -- Authorsgt from one
  part of lt! -- an ISSgt into their content.
• User error lt! -- an ISSgt cannot verify if
  content uploaded is correct. User is responsible
  for correctness of content
• System error lt! -- an ISSgt will not allow
  content edit/upload if the lt! -- an ISSgt DBMS is
  not available

10
Download content

• Users (lt! -- Authorsgt and lt! -- End-usersgt) can
  search and download course content
• for content lt! -- Authorsgt have created or
• for messages or personal info. entered by lt! --
  End-usersgt or
• (Exception) from content designated for sharing
  by all lt! -- Authorsgt (content
  and linked materials)
• User error lt! -- an ISSgt will not allow access
  to content except as allowed by lt! -- Sponsorgt
  policy
• System error lt! -- an ISSgt will not allow search
  or download of lt! -- an ISSgt content if lt!
  -- an ISSgt DBMS is unavailable.

11
Edit/upload content

• lt! -- Authorsgt can transmit the content they
  create to lt! -- Publishersgt for editupload into
  lt! -- an ISSgt
• lt! -- Publishersgt can upload one type of content
  at a time into lt! -- an ISSgt
• (Exception) lt! -- an ISSgt will allow existing
  content to be copied from one content object to
  another without upload.
• User error lt! -- an ISSgt cannot verify if
  content uploaded is correct. Users are
  responsible for correctness of content
• System error lt! -- an ISSgt will not allow
  content edit/upload if the lt! -- an ISSgt DBMS is
  not available

12
Upload messages/personal information content

• lt! -- End-usersgt can download, update, then
  upload personal information for sharing with
  other users.
• lt! -- End-usersgt (end-users) can upload messages
  for sharing with other lt! -- End-usersgt at any
  time.
• (Exception) lt! -- End-usersgt can sendreceive
  messages from other lt! -- End-usersgt via lt! -- an
  ISSgt, without uploading these messages into lt! --
  an ISSgt
• User error lt! -- an ISSgt cannot verify if
  content uploaded is correct in any sense. User is
  responsible for correctness of content
• System error lt! -- an ISSgt will not allow
  content edit/upload if the lt! -- an ISSgt DBMS
  is not available

13
Do User Messaging

• lt! -- Authorsgt can request lt! -- End-usersgt in
  their courses to download or upload messages via
  a lt! -- Asynchronous Messaging Systemgtor lt! --
  Synchronous Messaging Systemgt
• lt! -- Authorsgt or lt! -- End-usersgt can
  download/upload messages for sharing with other
  lt! -- End-usersgt at any time.
• (Exception) lt! -- Authorsgt can remove messages
  from their lt! -- Asynchronous Messaging
  Systemgt
• User error Messages that are deleted from a lt!
  -- Asynchronous Messaging Systemgt cannot be
  retrieved
• User error lt! -- Synchronous Messaging Systemgt
  message content is usually not saved by lt! -- an
  ISSgt
• System error lt! -- Asynchronous Messaging
  Systemgt message content managed by the lt! -- an
  ISSgt may be lost if the lt! -- an ISSgt Database is
  not backed-up.

14
Do Email

• Any user can access internal or external email
  systems via lt! -- an ISSgt to create, upload,
  download, update then upload messages for other
  users at any time.
• lt! -- an ISSgt does not manage email messages or
  message services
• (Exception) Users can create, upload, download,
  update then upload email messages via lt! -- an
  ISSgt, without uploading these messages into lt! --
  an ISSgt.
• User error Users cannot use lt! -- an ISSgt to
  manage or keep track of personal/private email
  messages or message content
• System error An email server may fail to send or
  receive email messages with or without notifying
  email users
• (Exception) Email servers will notify users if
  sent mail cannot be delivered

15
Access other Web content

• lt! -- Authorsgt can create content that contains
  Web hyperlinks
• Users can select hyperlinked items
• A selected item is downloaded into the Users
  client if the Web server can retrieve the item.
• (Exception) Users that select hyperlinked content
  will be disconnected from lt! -- an ISSgt after a
  certain elapsed time, unless they return to lt! --
  an ISSgt
• User error lt! -- an ISSgt will not allow access
  to its content directly from the Web
• System error lt! -- an ISSgt may unexpectedly
  terminate a user session if a user accesses Web
  items that attempt to upload information into
  lt! -- an ISSgt, or launch applications unknown to
  lt! -- an ISSgt.

16
Manage lt! -- an ISSgt content

• lt! -- IS System Developersgt create the
  representations, relations, and system components
  that provide users access to content managed by
  lt! -- an ISSgt.
• lt! -- an ISSgt is used to organize, store, query,
  retrieve or update content that is managed by lt!
  -- an ISSgt
• lt! -- an ISSgt uses a (relational) database
  management system to organize, query, retrieve or
  update content that is stored in its database
• (Exception) lt! -- an ISSgt stores data that
  identifies content, and controls access to
  content, stored as files in a networked file
  server, or as Web-based content accessed via the
  Web.
• User error lt! -- an ISSgt cannot be used to store
  arbitrary files for end-users.
• System error lt! -- an ISSgt cannot control
  updates to external content accessed via the Web.

17
Develop Test lt! -- an ISSgt

• lt! -- IS System Developersgt create the
  representations that other users utilize to
  create, insert, update or delete their content.
• lt! -- IS System Developersgt create, insert,
  update and delete content stored in lt! -- an ISSgt
  representations to test its proper operations
• (Exception) lt! -- IS System Developersgt cannot
  guarantee that all functions supported by lt! --
  an ISSgt have been tested.
• (Exception) lt! -- IS System Developersgt cannot
  guarantee that all functions supported by lt! --
  an ISSgt are re-tested every time any lt! -- an
  ISSgt function or operation is modified (updated).
• User error lt! -- IS System Developersgt expect
  that users will notify them if users encounter
  anomalies in lt! -- an ISSgt usage.
• System error lt! -- an ISSgt system components may
  fail to operate correctly even though they have
  been tested.