[Use Case]: SB-2 Frame-based representation, Inheritance of defaults, Reification

** SB-2 Frame-based representation, Inheritance of defaults, Reification

Description:

A unified student management system in a university that offers
undergraduate, graduate, and doctoral programs is exceedingly complex. It
encompasses admission as well as all stages of the study towards a
degree. Different programs have different admission requirements (e.g.,
they might require different types of documentation) and different policies
that govern the course of the study.

For instance, for admission, art departments might require creative work to
be submitted and/or interviews. Graduate programs might require (mandatory
or optionally) evidence of accomplishments such as completed projects or
published papers. Graduate programs might have "proficiency" requirements
(evidence that the student has attained knowledge in certain areas of
science at the undergraduate level; if not, a student might be required to
erase deficiencies in certain areas during their graduate years). PhD
programs often require various kinds of special examinations during the
course of the study.

Often there are also complex policies for tuition scholarships, graduation
requirements, etc. They govern who gets scholarships and at what level;
what it takes to graduate; etc. These policies often change over time, but
must all be retained and applied in appropriate situations due to
"grandfather rules" (a legal concept that states that students who were
admitted under a certain policy can request to have this policy in effect
thoughout their studies even if the policy changes in the interim).

Implications:

    - The data is inherently semistructured. Implementing such systems
      using the relational model (including Prolog-style predicates) is a
      quagmire. Even if implemented using the relational model, changes in
      data collection requirements and policies often require costly schema
      revision.  A flexible frame-based representation is called for in
      such situations.

    - This type of systems often require that certain information is
      inherited from higher-level descriptions, such as classes.  For
      instance, an academic adviser is the student's project or thesis
      adviser. If a student doesn't have such an adviser, then the academic
      adviser is inherited by default from an appropriate class description
      (e.g., a graduate or an undergraduate program director becomes the
      default adviser).

    - To be maintainable, policy rules (such as tuition waiver, graduation
      requirements) should be reified and represented as time-dependent
      objects. Depending on a concrete time point and the state of the
      underlying database at that time, student's eligibility to graduate
      or to receive tuition scholarship can be validated by fetching the
      appropriate policy object and then the corresponding policy rules can
      be applied.

Received on Sunday, 4 December 2005 20:51:40 UTC