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
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2. Use Case Review A Use Case tells a story of reaching a goal,
or a set of stories about reaching or failing.
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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
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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...”
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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.
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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
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7. Reusable Use Cases for an Information Sharing System: Global File Sharing System or Enterprise Portal
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8. Relations in <! -- an ISS>
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
Access other Web content
Manage <! -- an ISS> content
Develop & Test <! -- an ISS>
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9. Create/edit & upload content
<! -- Authors> create (insert) new content or edit (update) existing content
<! -- Authors> can transmit the content they create to <! -- Publishers> for edit&upload into <! -- an ISS>, else <! -- Authors> upload their content into <! -- an ISS>
<! -- Authors>/staff can only upload one type of content at a time into <! -- an ISS>
(Exception) <! -- an ISS> will allow existing content to be copied from one content object to another without upload.
<! -- Authors> can only edit (update) content they have individually created
(Exception) <! -- Authors> may copy and paste content created by other <! -- Authors> from one part of <! -- an ISS> into their content.
User error: <! -- an ISS> cannot verify if content uploaded is correct. User is responsible for correctness of content
System error: <! -- an ISS> will not allow content edit/upload if the <! -- an ISS> DBMS is not available
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10. Download content
Users (<! -- Authors> and <! -- End-users>) can search and download course content:
for content <! -- Authors> have created; or
for messages or personal info. entered by <! -- End-users>; or
(Exception) from content designated for sharing by all <! -- Authors> (content and linked materials)
User error: <! -- an ISS> will not allow access to content except as allowed by <! -- Sponsor> policy
System error: <! -- an ISS> will not allow search or download of <! -- an ISS> content if <! -- an ISS> DBMS is unavailable.
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11. Edit/upload content
<! -- Authors> can transmit the content they create to <! -- Publishers> for edit&upload into <! -- an ISS>
<! -- Publishers> can upload one type of content at a time into <! -- an ISS>
(Exception) <! -- an ISS> will allow existing content to be copied from one content object to another without upload.
User error: <! -- an ISS> cannot verify if content uploaded is correct. Users are responsible for correctness of content
System error: <! -- an ISS> will not allow content edit/upload if the <! -- an ISS> DBMS is not available
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12. Upload messages/personal information content
<! -- End-users> can download, update, then upload personal information for sharing with other users.
<! -- End-users> (end-users) can upload messages for sharing with other <! -- End-users> at any time.
(Exception): <! -- End-users> can send&receive messages from other <! -- End-users> via <! -- an ISS>, without uploading these messages into <! -- an ISS>
User error: <! -- an ISS> cannot verify if content uploaded is correct in any sense. User is responsible for correctness of content
System error: <! -- an ISS> will not allow content edit/upload if the <! -- an ISS> DBMS is not available
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13. Do User Messaging
<! -- Authors> can request <! -- End-users> in their courses to download or upload messages via a <! -- Asynchronous Messaging System>or <! -- Synchronous Messaging System>
<! -- Authors> or <! -- End-users> can download/upload messages for sharing with other <! -- End-users> at any time.
(Exception) <! -- Authors> can remove messages from their <! -- Asynchronous Messaging System>
User error: Messages that are deleted from a <! -- Asynchronous Messaging System> cannot be retrieved
User error: <! -- Synchronous Messaging System> message content is usually not saved by <! -- an ISS>
System error: <! -- Asynchronous Messaging System> message content managed by the <! -- an ISS> may be lost if the <! -- an ISS> Database is not backed-up.
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14. Do
Any user can access internal or external systems via <! -- an ISS> to create, upload, download, update then upload messages for other users at any time.
<! -- an ISS> does not manage messages or message services
(Exception): Users can create, upload, download, update then upload messages via <! -- an ISS>, without uploading these messages into <! -- an ISS>.
User error: Users cannot use <! -- an ISS> to manage or keep track of personal/private messages or message content
System error: An server may fail to send or receive messages with or without notifying users
(Exception) servers will notify users if sent mail cannot be delivered
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15. Access other Web content
<! -- Authors> can create content that contains Web hyperlinks
Users can select hyperlinked items
A selected item is downloaded into the User’s client if the Web server can retrieve the item.
(Exception) Users that select hyperlinked content will be disconnected from <! -- an ISS> after a certain elapsed time, unless they return to <! -- an ISS>
User error: <! -- an ISS> will not allow access to its content directly from the Web
System error: <! -- an ISS> may unexpectedly terminate a user session if a user accesses Web items that attempt to upload information into <! -- an ISS>, or launch applications unknown to <! -- an ISS>.
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16. Manage <! -- an ISS> content
<! -- IS System Developers> create the representations, relations, and system components that provide users access to content managed by <! -- an ISS>.
<! -- an ISS> is used to organize, store, query, retrieve or update content that is managed by <! -- an ISS>
<! -- an ISS> uses a (relational) database management system to organize, query, retrieve or update content that is stored in its database
(Exception) <! -- an ISS> 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: <! -- an ISS> cannot be used to store arbitrary files for end-users.
System error: <! -- an ISS> cannot control updates to external content accessed via the Web.
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17. Develop & Test <! -- an ISS>
<! -- IS System Developers> create the representations that other users utilize to create, insert, update or delete their content.
<! -- IS System Developers> create, insert, update and delete content stored in <! -- an ISS> representations to test its proper operations
(Exception) <! -- IS System Developers> cannot guarantee that all functions supported by <! -- an ISS> have been tested.
(Exception) <! -- IS System Developers> cannot guarantee that all functions supported by <! -- an ISS> are re-tested every time any <! -- an ISS> function or operation is modified (updated).
User error: <! -- IS System Developers> expect that users will notify them if users encounter anomalies in <! -- an ISS> usage.
System error: <! -- an ISS> system components may fail to operate correctly even though they have been tested.
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