Cyclic Computations - Essay Example

Question #4:

i.

SQL

Relational Algebra

select * from Programme as Programme(aCode,aTitle), ProgrammeVersion as ProgrammeVersion(bCode,bVersion, bSpecification) where aprogrammeCode = bprogrammeCode

(RENAME(aprogrammeCode, aTitle)( Programme)) JOIN aprogrammeCode = bprogrammeCode (RENAME(bprogrammeCode, bVersion, bSpecification)( ProgrammeVersion))

ii.

SQL

Relational Algebra

select * from UnitDelivery as UnitDelivery (alecturerId, aunitCode,ayear), ProgrammeUnits as ProgrammeUnits (bprogrammeCode,bunitCode) where alecturerId=’jjb’, aunitCode=bunitCode and ayear<currYear()

(RENAME(alecturerId, aunitCode, ayear)( UnitDelivery)) JOIN alecturerId = ‘jjb’ JOIN aunitCode = bunitCode JOIN ayear<currYear() (RENAME(bprogrammeCode, bunitCode)(ProgrammeUnits))

iii.

SQL

Relational Algebra

select * from Unit as Unit(aunitCode,aunitTitle), UnitDelivery as UnitDelivery(blecturerId,bunitCode, byear) where (blecturerId=’jjb’ and byear<currYear()) and (blecturerId=’amb’ and byear>currYear())

(RENAME(aunitCode, aunitTitle)( Unit)) JOIN blecturerId = ‘jjb’ JOIN byear<currYear() JOIN blecturerId = ‘amb’ JOIN byear>currYear() (RENAME(blecturerId, bunitCode, byear)(UnitDelivery))

iv.

SQL

Relational Algebra

select * from UnitDelivery as UnitDelivery(alecturerId,aunitCode, ayear), Programme as Programme(bprogrammeCode,bprogrammeTitle), ProgrammeUnits as ProgrammeUnits(cprogrammeCode,cunitCode) where aunitCode=cunitCode, bprogrammeTitle=’Database Systems’ and ayear<currYear()

(RENAME(alecturerId, aunitCode, ayear)( UnitDelivery)) JOIN aunitCode = cunitCode JOIN ayear<currYear() (RENAME(bprogrammeCode, bprogrammeTitle)(Programme)) JOIN bprogrammeTitle=’Database Systems’ (RENAME(cprogrammeCode, cunitCode)(ProgrammeUnits))

Question #11:

Precedence Graph

As seen, the graph is not serializable because the graph is acyclic. Conflicts may occur which are likely to generate erroneous outcomes. Notice the precedence graphs are acyclic, that is, they do not have loops. Thus, they cannot represent cyclic computations. Since many of the computations in operating systems are cyclical, this is a strong restriction.

Question #12:

1. )

            The Workspace is a collection of pathways, as well as custom annotations and other private data. Custom annotations may include folders and text fields functionally classifying a gene (for example, as a receptor) or linking it to a specific disease. Users may add both new nodes and links, which will be saved to the Workspace.

ii.)

            The Buffer block redistributes the input samples to a new frame size, larger or smaller than the input frame size. Buffering to a larger frame size yields an output with a slower frame rate than the input, as illustrated below for scalar input.

iii.)

            System managers may specify physical block sizes and database designers, subject to constraints set by the machine architecture and operating system. One important aspect of file and database design is producing a good match between physical "pages" and logical units like tables and records.

iv.)

            Once a transaction has been committed (completed), the results of a transaction are permanent and can survive future system and media failures. DBMSs control the storage of data in a variety of ways, depending on the type of data and users and their relative locations.