ACCESSING DATABASE QUALITY
The survey of informations patterning and database design is going more of import in today ‘s universe because logical database design is independent of the system environment and helps the terminal user to see a practical position of how the database will work when it is physically designed. It besides helps to cognize if there will be an mistake in the database when it is designed ( Teorey et al 2009 ) .Database design is an of import facet of working with a database, besides good quality database that a user is satisfied with “ does non merely go on ” if it ‘s non designed decently and carefully. No affair how good a DBMS is, it will execute severely with a ill designed database ( Rob, Coronel and Crockett 2008 ) .This study is non traveling to depict the tools and notations used in DatabaseDesign but it ‘s traveling to discourse how these tools help in planing quality database.
- Meaning of Quality Databases and Framework for Evaluating Database Quality
In logical database modeling, a batch of factors have to be considered when looking at quality, some of the factors are but non limited to scalability, public presentation, velocity, stop user, cost, ownership and informations unity.
These factors help in bring forthing a database of high quality ( Hoxmeier 1997 ) . There are different types of logical informations patterning attacks but I will be concentrating more on Entity Relationship ( ER ) theoretical accounts, Unified Modelling Language ( UML ) theoretical accounts which includes tools like usecase diagram and description and Enhanced Entity-Relationship Modelling ( EER ) in this paper, because of its simpleness and readability they are the most popular modeling attack ( Teorey et al 2009 ) .Nowadays, an international criterion is in topographic point for measuring the quality of package merchandises but the same ca n’t be said of conceptual theoretical accounts, they are evaluated in pattern in an “ ad hoc ” manner ( merely for a peculiar intent ) . A good quality conceptual theoretical account may take to a good quality database system while a good quality conceptual theoretical account might non be implemented decently besides a hapless quality conceptual theoretical account might be improved upon subsequently in the design stages. This ground makes conceptual theoretical account affect the “ efficiency and rightness ” of a database system because this factors depend on the quality of the conceptual theoretical account, a high quality conceptual theoretical account will take to a high quality database system ( Moody 2005 )As discussed in ( Batini, Ceri and Navathe 1992 ) logical database theoretical account is made up of a normalized theoretical account of the database set to the 3rd normal signifier, it besides consist of many elements that make up a database but non specific to any database direction system or database execution. At this point the public presentation factors of the database are neither a major consideration nor the applications that will be utilizing the database although this is argued by Hoxmeier ( 1997 ) that public presentation should be considered as an facet of overall database quality. The major ground behind the logical design is to construct a theoretical account of how the database will look like when capturing the informations needed by the users.
It is farther argued in ( Batini, Ceri and Navathe 1992 ) how critical the logical design stage is to database design because the logical design is done by professionals in cooperation with the database users to bring forth a database good quality. Evidence of this is shown in the illustration of planing an thought direction system where some premises where made based on demands given by the client. This was sorted out finally after run intoing the client and demoing them the ER and UML theoretical account because the client was able to understand the theoretical accounts presented to them through ER diagram, usecase diagram etc which are all constituents of logical database design.Harmonizing to ( Hoxmeier 1997 ) it is stated that rating of overall database quality can be assessed by four major factors which are ;
- Database Process Quality:When looking at this factor, we have to first of all expression at the design procedure which is driven by the demands and the major demands of the terminal user of the database. An illustration of this is the “ Courtesy Coach Company ” assignment where we used ER & A ; UML theoretical account to come up with a logical design of the database. Although some of the solutions to the scenario might non be perfectly right but they were of good quality.
- Database Data Quality: This factor largely deals with the physical database design or the care of the informations in the database.
The age of the information is considered as a metric for measuring informations unity.
- Database Semantic Quality:Harmonizing to Hoxmeier ( 1997 ) Storey and Wang presented an extension to the traditional ER theoretical account to add quality demands into conceptual design of database which are database “ quality informations and merchandise quality informations ” but the implicit in statement of this is that there should be a difference between the quality demands and the database belongingss. It is further discussed that it is hard to plan a database with high semantic value without anterior important experience and sphere cognition.
- Database Behaviour Quality:This factor deals with the design, building and execution of a solution sphere that provides entire solution to the job sphere as discussed in ( Hoxmeier 1997 ) .
The ER theoretical account is a theoretical account that describes informations in footings of entities, properties and the dealingss between them frequently represented by diagrams called entity relationship diagrams ( Riordan 2005 ) .
Initially the most hard portion faced by interior decorators and terminal users when planing databases is that they tend to see informations and its usage in different ways. This is the ground why most of the designs produced does non run into the user ‘s demands, the ER theoretical account is a design tool that has the reply to this because it communicates the design to the user in a clear and non-technical manner ( Connoly and Begg 2010 )As discussed in ( Kesh 1995 ) organisations depend critically on their informations thereby doing the demand of high quality database of import. It is further discussed that since ER theoretical accounts stand at the nucleus of database design today, the quality of a database can merely be met merely if the ER theoretical account is of high quality every bit good.
In account, this writer is seeking to state that a good database has to be of high quality and the criterion of the quality has to be shown on the logical design of the database utilizing ER theoretical accounts. An illustration of this is the “ Courtesy Coach Company ” assignment where we came up with a logical design of the client ‘s database but the nucleus of this design was the ER theoretical account even though there were other theoretical accounts like the UML, this supports Kesh ‘s statement of ER theoretical account standing at the nucleus of database design.It was further discussed in ( Kesh 1995 ) that we can specify the quality of a database relevant to aim because ER theoretical accounts are used to plan a database to be used by an organisation, any choice step should see the ends of the organisation. This theoretical account should besides be apprehensible to the user groups involved and besides supply a technically sound platform that can be used to make a complete and consistent database.Finally, the ER theoretical account can non bring forth really high quality of a database design because it does non to the full back up the representation demands of much more complex database applications like Computer Aided package Engineering ( CASE ) and Computer Aided Design ( CAD ) hence the demand for an advanced modeling called Enhanced Entity-Relationship Modelling ( Connolly and Begg ) .
The EER theoretical account combines the patterning constructs of the ER theoretical account and UML theoretical account to convey out a design of higher quality because a database design of high quality should be flexible plenty to accommodate to the demands of information demands and alteration in informations ( Rob, Coronel and Crockett 2008 ) . There are three major grounds for the usage of EER harmonizing to Houldcroft ( 2011 ) and they are:
- Integrity, Consistency, Correctness
- a different manner of looking at the existent universe to assist us understand it
- may assist to avoid traps e.
g Fan Traps, Chasm Traps
Looking at the above grounds, one of the major grounds behind the EER theoretical account is the ability of it to assist avoid traps for illustration the fan trap which is a state of affairs where “ two or more 1: many relationships fan out from the same entity ” ( Connolly and Begg 2010 ) .The basic constructs used by the EER theoretical account are specialization/generalization, entities collection, and composing. Along with the three major grounds for the usage of EER theoretical account it is besides used to plan a database utilizing object-oriented construct like heritage, abstraction, collection and coherence ( either high or low ) which are all used in system design ( Kendall and Kendall 2011 )
Having looked at ER theoretical account, another theoretical account used for database design is the UML. This theoretical account is besides in common usage today chiefly because it puts the user of the database in the Centre of its design utilizing graphical linguistic communication. Most of the design system in topographic point today focus largely on the hardware and package, this is where UML comes in because it uses a design scheme whereby the system is built around the people you have in head to utilize the database ( Naiburg and Maksimchuk 2001 ) . The account is justified in Hoxmeier ( 1997 ) which says meeting the outlook of the terminal user is one facet of the overall quality of a good database even though this is non the lone 1.Use-case is one of the tools used in UML and it is used in giving a contemplation of how the system will work when implemented ( Muller 1999 ) .
A usage instance theoretical account besides has four major effects on planing database of high quality harmonizing to Muller ( 1999 ) and they are:
- It helps to stand for an atomic dealing through the systems and this dealing helps in planing logical database and besides the architecture used in dealing processing demands of the system.
- It helps in demoing how the database will utilize informations elements.
- It besides provides an substructure for mensurating database merchandise
- Finally it helps to supply the footing for formalizing database merchandise. This is one of the most of import consequence of usecase because as the physical design of the database is traveling on you can formalize the work done by associating it back to the usecase, finally this helps in coming up with a database that meets the user ‘s demand which in bend contributes to the quality of a database.
( Muller 1999 ) .The diagram on the following page shows an illustration of how a typical use-case digraph looks. It shows the histrions and the actions they are making.
There are besides use-case descriptions that help to break simplify the design and an illustration from the assignment is shown below:Usecase: Position Vehicle DetailsActors
- User has entree to system
- User chinks on vehicle
- User selects the vehicle the wish to see information about
- User views the selected vehicle information
Fig 5.1: An illustration of Use-Case diagram ( LDD Group Assignment )
- Correctness and Quality in Database Design
The issue of rightness and quality is a controversial issue in the designing of database in the universe today. In this subdivision I will take a expression at what academic documents have said about this issue.
When looking at quality of a database design, we besides have to look at informations quality and information quality has four major dimensions which are but non limited to: completeness, deficiency of ambiguity, meaningfulness and rightness. Besides data quality means different thing to different users ( Storey and Wang 1997 ) .As discussed further in Storey and Wang ( 1997 ) “ rightness ” is merely one of the dimensions when looking at informations quality so we ca n’t merely establish the quality of a database design on its rightness but it has to be considered before we can state a database is of high quality.Besides ( Olson 2003 ) said “ a right database has the capableness of run intoing all the demands, better informations quality as discussed above, better informations unity and extinguish informations redundancy but it is non sufficient entirely for planing a database of high quality.
Finally, a high quality database design is a database design that has to the full met the user demands and is scalable plenty to suit betterments as clip goes on, the four suggested standards for mensurating it are database procedure quality, database informations quality, database informations quality and database behaviour quality. Database design rightness on the other manus is a design that has the necessary informations theoretical account to back up user demands, better informations quality and better informations unity.Besides the usage of ER, EER, Use-Case helps in capturing the concern demands which in bend brings client satisfaction which is one end of quality database design.
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