OSMIS Technical Specification
3.1 Design Overview
The database design is based on a traditional entity-relational model.
Some effort was put into developing a design that would be easy to add
to, and modify for use in non-South African countries. However, there
is clearly a trade-off with a heavily generalised design, with respect
to ease of use and development. A design that is very general may
become difficult to work with and understand, and is also likely to
incur higher computational overheads. On the other hand a very
specific design may be fast and easy to work with, but difficult to
add to later.
The compromise chosen applies the following principles:
Some Implementation Notes
- Abstract out some of the data common to all countries - for
example the concepts of grades, promotion decisions, languages,
people and schools
- Group data that is very country-specific into separate tables
- Do not enforce strict constraints on the data, so that in cases
where the data is not meaningful, it can simply be ignored. Thus the
business logic is left to the software.
- Use incremental integer IDs as primary keys for every
table. This avoids placing strong constraints on the data.
- Database tables are specified as either containing static
data or read-write data. In the former case, the tables are
populated with data when the system is installed and are never updated
by the system (they may be updated administratively if the static data
needs to be changed). In the latter case, the tables hold normal
transactional data and may be read from and written to.
- The naming convention <tablename>PA has been used to
name tables that contain data relevant to a specific academic
year. PA stands for per annum.
- There is no direct link from learners to educators. Thus to
represent the concept of registration classes and/or class teacher, a
subject called Registration should be created. Then each class
educator should be allocated a registration subject and the
corresponding learners should be allocated that subject if they belong
to the educator's class.
- The concept of subject levels (i.e. HG, SG, LG, OG) is still an
outstanding issue. Currently it is implemented at the learner
level. That is, an educator teaches a particular subject (with no
regard for subject level) and the learners that take that subject,
take it at a specific subject level. How well this maps to
the real world still needs to be determined.