COMP 6471 Software Design Methodologies. Winter 2006 Dr Greg Butler http://www.cs.concordia.ca/~gregb/home/comp647-w2006.html. The CU WME Design Case Study.
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Dr Greg Butler
Concordia University Work Management Environment (CU WME) provides support for an organisation of people who produce and publish documents
How do components distribute responsibilities and what are their dependencies?
Separate mechanisms from policy.
How do components distribute responsibilities?
What are their dependencies?
Separate mechanisms from policy.
Which set policy, which provide implementation to enforce policy, which provide basic mechanisms?
RBAC (Role Based Access Control) concepts
Role (enumerated list)
Operation (eg, read, write, …)
Object (= Resource, ie Document/File)
Permission of Role to perform an Operation on Object
RBAC1 allows role hierarchy (DAG)
RBAC2 adds constraint condition (ie lock exists on Object) to modify permissions
Does not need to define specific roles for the system, not Operations, nor Objects: these might be requirements from other Components.
Eg, role of project management from PM (C6)
Eg, operation read for Object file(“…”) from FM (C2)
Unix File System
File is stream of bytes to provide uniform abstraction
Directory hierarchy mixes files/directories/links as entries
File identified by pathname (cf URI)
Unix permissions (rwx) for roles (user, group, other)
Does CUWME FM need its own access control?
Who provides storage for UM?
How to manage copies of files? Versions of files?
Back-up in FM
What are mechanisms
What are policies for back-up, where are they set
What storage (ie files) are needed for back-up?
Are these managed by FM?
Do these have back-up needs?
File replication in distributed system
Same file exists in different location
What does “same” mean here? Implications for file operations are …
How is this managed by FM?
Are files atomic?
How does FM relate to Change Mgmt and Document Mgmt?
Does FM set policy (ie define) how a document is stored by FM? How a change is stored in FM? How a change is named?
Do we back-up files or documents? If both, how is doc back-up related to file back-up?
Is a back-up a change, activity, copy, version, …
Concurrent Versions System (CVS)
Is version control management system
Versions of what? …for CVS source code files, binaries, documentation
Check-out/check-in to manage concurrent access
Version branches … which can be merged later (manually)
Tracks versions, not changes
Storing deltas (ie changes) is an implementation optimization
Version of file or document or resource or …?
Dependency on FM? for storage
Which operations create a new “version”?
Which do not?
How do permissions on X carry over to permissions on version of X? or copy of X …
Who sets this policy? Where?
Do change management of files
This is basic building block.
Do change management of documents
Remember documents are composite/recursive.
Look at basic concepts of web session or DB transaction or Command pattern
Session is a sequence of activities by a user (from beginning to end)
Activity is execution of an operation (C1) or command (GOF) or activity (C6)
AM (C4) records/logs activities with info
Session, activity, user, role, …
Who is responsible for session creation?
Collaborate with UM (C1) to ensure user has permission for the activity (operation).
Can a user have many sessions at once?
Where are command objects created? Executed? Recorded?
Does FM supply storage for log?
How do operations which create versions communicate to CM (C3) that a version has been created?
Remember that AM provides mechanisms, not policies.
…is this just Document Management?
It should provide mechanisms, not policy. However, it must provide mechanisms that support the enforcement of policy, eg concurrency.
Does this component need to define specific roles and permissions? Or can this be done separately using UM (C1)?
Think of a document as an XML document, ie composite.
How do you capture dependencies between a document and its parts? And the files? And its build process? [ie, compare document publication with software development]
You need back-up and versions of documents: can you simply rely on FM back-up facility?
I do not know of any good CP/DM(C5) system to refer you to as an example.
“groupware” tends to focus on calendars, chat, notification rather than documents themselves.
“issue tracking” tends to just look at issues and their resolution, but not document changes (or source code changes)
OpenText Livelink is a Canadian example, but it does everything in CU WME and more
Lotus Domino from IBM is also of interest
Keep the scope simple.
This is the place for policy – maybe not the only place.
Sequence of activities, resources (ie roles) required, and schedule (in timeunits of duration).
Set start date, assign users to roles.
Monitor project progress:
Collaborate with UM (C1) so that user session is associated with a project and role: assigned activities are RBAC “operations” on certain “objects”.
Collaborate with AM (C4) to check whether activities are done.
Composite pattern for project? Or for process?
So a project can be a sequence of activities and/or subprojects. Allows easier definition of projects.
Set/enforce policy? User can only work on assigned projects? User can only do scheduled activities?
Again, difficult to find a simple example for you.
Java open source projects include “Ganttproject” (a MS Project in Java) and “teamwork”.
OpenText Livelink has project management.