Application Design (2) Database – IS 240 Lecture #23 – 2004-04-15 M. E. Kabay, PhD, CISSP Dept...

Application Design

(2)Database – IS 240Lecture #23 – 2004-04-15

M. E. Kabay, PhD, CISSPDept of Computer Information Systems

Norwich University [email protected]

mailto:[email protected]

2 Copyright © 2004 M. E. Kabay. All rights reserved.

TopicsWhere to Enforce Constraints?Types of ConstraintsSecurityControlHomework


Where to Enforce Constraints (1)?

DBMS / proCentral control over data constraints:

Define once, apply consistently to all applications

Change for all applications by modifying one rule

May need to examine all records -- fasterDBMS / con

Not all DBMS engines handle constraints fully or well


Where to Enforce Constraints (2)?

Application / proMay be easier to implement constraints in

appsSome constraints are application-

dependentSpecific business rulesSome domain constraints such as

assigning an input to a specific field (e.g., PATIENT.Name vs DOCTOR.Name)

General principle: try to enforce constraints in DBMS first, then move to application.


Exercise: Constraint Implementation -- Hospital

Consider the hospital DB we have been using in the last several lectures

Suggest constraints that would be best implementedIn the DBMS metadataIn an application program


Types of Constraints

DomainUniquenessRelationship

Referential integrityRelationship cardinality

Business rules


Domain Constraints

What type of data can be entered in a field?How can constraining data type help the

user?How long can the input be?

Why would you care about the length of a field?

Are there masks (patterns) that reflect the way data are to be entered and/or stored?Give several examples of masks you might

use in a hospital DB


Domain Constraints (cont'd)Optional fields

Implies acceptance of null entriesIs a null entry always the same as a blank

or a zero?Give examples of optional and mandatory

fields you might see in the hospital DBRequired / Mandatory fields

Can supply initial (default) valuesMany form designers on Web use * to mark

required fieldsCan signal (flag) missing data either on exit

from field or on completion of formDiscuss pro/con of each strategy


Uniqueness Constraint

Simple to define in DBMS as attribute of a specific field

Usually define an item as an index to accomplish uniqueness checking very quicklyRoughly how long does it take to read a

record or a block of records from disk?Without an index, how would the DBMS

enforce the uniqueness constraint?Why does creating an index speed up

uniqueness checking?


Referential Integrity

Referential integrity means. . . what?Discuss examples of failures of referential

integrity that might occur in the hospital DBHow is it possible to develop a breach of

referential integrity?


Relationship Cardinality

Consider the relationship between patient, doctor and prescription in a CURRENT_PRESCRIPTION table.Can a prescription exist without a patient?

Without a doctor?What is the cardinality of prescription to

patient? Prescription to doctor? Prescription to (Patient, Doctor)?

Could the DBMS enforce a rule thatOnly one prescription must be defined for

any given patient?How?


Relationship Cardinality (1)

A row missing a required parent or a required child is called a fragment.

A child missing a mandatory parent is called an orphan.

Give examples from the hospital DB of aMandatory-to-mandatory (M-M) constraintMandatory-to-optional (M-O) constraintOptional-to-mandatory (O-M) constraintOptional-to-optional (O-O) constraint


Relationship Cardinality (2)

Examples from a hospital DBM-M: A patient must have a bed and a bed

must have a patient to be recorded in the current list of in-patients

M-O: A doctor may have one or more patients but a patient must be assigned at least one doctor

O-M: A prescription must have a patient but a patient does not necessarily have a prescription

O-O: A session of grand rounds may be scheduled without knowing which doctor(s) will present; a doctor may or may not participate in grand rounds.


Preventing Fragments: Parent RecordsGive examples from the hospital DB of each

rule from Figure 10-19 (reproduced below):

Insert Modify key Delete

M-MCreate at least one

childChange matching key of all children

Delete all children OR reassign all

children

M-O OKChange matching keys of all children

Delete all children OR reassign all

children

O-MInsert new child OR appropriate

child exists

Change key of at least one child OR appropriate child

exists

OK

O-O OK OK OK

Typ

e o

f re

lati

on

ship

Proposed Action on Parent


Business Rules

Give examples of business rules in a hospital DB that would apply toSalary increases for nurses as a function

of last year’s profitsWhether a doctor could be entered into the

DOCTOR tableAcceptability of an insurance company as

a payerHow the head of a service (e.g., ICU, OR,

Internal Medicine, Dermatology) is selectedWould you implement these rules in the

DBMS metadata or in an application program?


Security Basics

Basic conceptsConfidentialityControl or possessionIntegrityAuthenticityAvailabilityUtility

MechanismsIdentification & AuthenticationUser-specific views


Confidentiality

Restricting access to dataProtecting against unauthorized disclosure of

existence of dataE.g., allowing industrial spy to deduce

nature of clientele by looking at directory names

Protecting against unauthorized disclosure of details of dataE.g., allowing 13-yr old girl to examine

HIV+ records in Florida clinic


Possession

Control over informationPreventing physical contact with data

E.g., case of thief who recorded ATM PINs by radio (but never looked at them)

Preventing copying or unauthorized use of intellectual propertyE.g., violations by software pirates


Confidentiality & Possession Losses

Locating Disclosing Observing, monitoring, and acquiring Copying Taking or controlling Claiming ownership or custodianship Inferring Exposing to all of the other losses Endangering by exposing to any of the other losses Failure to engage in or to allow any of the other losses

to occur when instructed to do so


Integrity

Internal consistency, validity, fitness for useAvoiding physical corruption

E.g., database pointers trashed or data garbled

Avoiding logical corruptionE.g., inconsistencies between order header

total sale & sum of costs of details


Authenticity

Correspondence to intended meaningAvoiding nonsense

E.g., part number field actually contains cost

Avoiding fraudE.g., sender’s name on e-mail is changed

to someone else’s


Integrity & Authenticity Losses

Insertion, use, or production of false or unacceptable data

Modification, replacement, removal, appending, aggregating, separating, or reordering

MisrepresentationRepudiation (rejecting as untrue)Misuse or failure to use as required


Availability

Timely access to dataAvoid delays

E.g., prevent system crashes & arrange for recovery plans

Avoid inconvenienceE.g., prevent mislabeling of files


Utility

Usefulness for specific purposesAvoid conversion to less useful form

E.g., replacing dollar amounts by foreign currency equivalent

Prevent impenetrable codingE.g., employee encrypts source code and

"forgets" decryption key


Availability & Utility Losses

Destruction , damage, or contaminationDenial, prolongation, acceleration, or delay in

use or acquisitionMovement or misplacementConversion or obscuration


Security in DBMS

User-specific viewsVertical security: limit columns (fields)Horizontal security: limit rows (records)

ImplementationsIncorporate user-name or role in recordsUse different forms, reports for different

peopleGive examples of how a hospital application

might apply security restrictions to its DB


Control in DB Applications

Two types of controlLogic or flow: how to move from one

forms or report to anotherTransaction integrity – subject of later

lecturesLogic flow can be controlled by menus

An entire form can present a menu of choices

Or in a GUI, pull-down menus can unfold into secondary menus to show options


Homework

Review all of chapter 10 carefully using SQ3RSurvey all of Kroenke’s Chapter 11 using the SQ

phases of SQ3R in preparation for Thursday’s class – Ch 11 covers very complex issues

REQUIRED: By Thursday the 22nd of April,Complete and hand in questions 10.24 to

10.48 for 50 pointsOPTIONAL: By Thursday the 29th

For 4 points of extra creditComplete the Group II questions on page 291


DISCUSSION

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