Software Development(Database):
Hierarchical databases are the oldest.
To access a data entity within a hierarchical database, it requires the knowledge of which branch to start with and which route to take through each layer until the data is reached.
Relational databases use INDEXES to search procedure.
Note: Links cannot be created between different branches and leaves on different layers.
Data Dictionary: contains data elements, their description and their relationships. It also contains info like data format, usage and origin.
Mechanism that ensures that a failed transaction or system failure returns the subject to a meaningful point in a process. .....checkpoint
Component of Expert system that matches facts against patterns and determines which rules are acceptable based on algorithms(that dictate system behavior) ....Inference engine
OS allows sequential use of object without refreshing it what issue can arise: Disclosure of residual data.
Network Based database Model:
It is a flexible way of representing objects and their relationships.
Its distinguishing feature is the schema; viewed as a graph in which objects are nodes and relationships are arcs.
It is not restricted to hierarchy or lattice. NBDB is base upon hierarchical data model but not restricted to it.
Instead of being constrained of how to go from one branch to another and from one parent to a child to find a data element. NBDB allows each data element to have multiple parent and child records.
This gives NBDS a redundant network like structure instead of a strict tree like structure.
A network model forms a structure similar to mesh topology for sake of redundancy. and allows quick retrieval of data compared to hierarchical model.
OODB vs RDBMS
1. Have procedures RDBMS need application to have data procedure
2. OODB are more dynamic.
3. OODB handle audio, video, document
4. OODB has classes to define attributes and procedures of its objects
CC uses PP as a specific security solution and these are reusable.
Network and Network Security(Network devices and configurations) ----RED book--ITSEC-- TNI
Operating system----Orange book-- US--TCSEC--DOD
Using automated Tools and mechanism to reduce cost and streamline the process ....CASE (Computer aided software engineering)
Foreign key - attribute of one column of a table related to primary key of another table.
Schema -- describes structure of database.
Data dictionary - central repository of data elements and their relations.
OLE DB: Object Linked and embedded database:
1. It separates data components that run as a middleware on client or server.
2. It provides a low-level interface to link information across different databases, and provides access to data no matter where it is located or how it is formatted.
3. OLE DB is replaced by ODBC (Open Database Connectivity), ODBC supports a wide variety of non-relational databases and spreadsheets that do not necessarily implement SQL.
4. A set of COM(component object model, MS)-based provide applications with uniform access to data stored in diverse data sources.
5. OLE DB (because it is COM based) is limited to use by MS windows-based client tool..
6. It allows different applications to access different types of and source of data.
OLE DB sources, the CommandType property describes the value of the CommandText property.
ODBC sources, the CommandText property functions exactly like the SQL property, and setting the property causes the data to be refreshed
[OLE DB and ODBC are APIs that provide access to a range of data sources. Microsoft designed ODBC to access SQL data and OLE DB to access any type of data in a COM environment. Many people don't entirely understand the factors that led Microsoft to implement OLE DB. Others overestimate the current role of OLE DB in the corporate and Web-development environments.]
[architecture of ODBC and OLE DB. Both rely on specialized components (drivers in ODBC and providers in OLE DB) that connect to the data source. Within ODBC, a driver usually acts as a proxy component, passing in SQL commands to the DBMS and returning result sets. An OLE
DB provider accepts data in any query language it supports (not only and not necessarily SQL) and returns recordsets. A data provider encapsulating a DBMS (ODBC) is limited to passing SQL commands to the underlying database server. A data provider that renders a nonrelational data store (e.g., an email store) accomplishes the additional task of creating the recordset and populating it with the data. Such a provider might support a query language that is simpler than SQL. For example, to return email from a customer, the provider needs to know only the name of the sender. This type of command]
ADO:
ActiveX Data Objects:
Characteristics of ADO:
1. It is a high level data access programming interface to an underlying data access technology (OLE DB)
2. It is a set of COM objects for accessing data sources and not just database access.
3. It allows a developer to write program that access data without knowing how the database is implemented.
4, SQL commands are not required to access a database when using ADO.
Row/Tuple/record/ cardinality
column/ Attribute
Schema of a Database:
1. Schema of a db is system is structure described in a formal language(supported by DBMS).
2. In relational db, schema defines: tables, fields, relationships, views, indexes, packages, procedures, functions, functions, queues, triggers, types, sequences, materialized views, synonyms, db links, directories, Java, XML, schemas, are stored in data dictionary.
Note: Schema data = table, field.......
The best programmers use high cohesion because different modules(units) need to pass data and communicate(they can't be totally cohesive ) and low coupling because lower the coupling better the software design because it promotes module independence.
Software Testing Approaches:
1. Top down Testing: In this approach testing is conducted from main module to sub module. if the sub module is not developed a temporary program called STUB is used for simulate the submodule.
Advantages:
- Advantageous if major flaws occur toward the top of the program.
- Once the I/O functions are added, representation of test cases is easier.
- Early skeletal Program allows demonstrations and boosts morale.
Disadvantages:
- Stub modules must be produced
- Stub Modules are often more complicated than they first appear to be.
- Before the I/O functions are added, representation of test cases in stubs can be difficult.
- Test conditions ma be impossible, or very difficult, to create.
- Observation of test output is more difficult.
- Allows one to think that design and testing can be overlapped.
- Induces one to defer completion of the testing of certain modules.
Bottom up testing: In this approach testing is conducted from sub module to main module, if the main module is not developed a temporary program called DRIVERS is used to simulate the main module.
Advantages:
- Advantageous if major flaws occur toward the bottom of the program.
- Test conditions are easier to create.
- Observation of test results is easier.
Disadvantages:
- Driver Modules must be produced.
- The program as an entity does not exist until the last module is added.
Stubs and Drivers
It is always a good idea to develop and test software in "pieces". But, it may seem impossible because it is hard to imagine how you can test one "piece" if the other "pieces" that it uses have not yet been developed (and vice versa).
A software application is made up of a number of ‘Units’, where output of one ‘Unit’ goes as an ‘Input’ of another Unit. e.g. A ‘Sales Order Printing’ program takes a ‘Sales Order’ as an input, which is actually an output of ‘Sales Order Creation’ program.
Due to such interfaces, independent testing of a Unit becomes impossible. But that is what we want to do; we want to test a Unit in isolation! So here we use ‘Stub’ and ‘Driver.
A ‘Driver’ is a piece of software that drives (invokes) the Unit being tested. A driver creates necessary ‘Inputs’ required for the Unit and then invokes the Unit.
Driver passes test cases to another piece of code. Test Harness or a test driver is supporting code and data used to provide an environment for testing part of a system in isolation. It can be called as as a software module which is used to invoke a module under test and provide test inputs, control and, monitor execution, and report test results or most simplistically a line of code that calls a method and passes that method a value.
For example, if you wanted to move a fighter on the game, the driver code would bemoveFighter(Fighter, LocationX, LocationY);
This driver code would likely be called from the main method. A white-box test case would execute this driver line of code and check "fighter.getPosition()" to make sure the player is now on the expected cell on the board.
A Unit may reference another Unit in its logic. A ‘Stub’ takes place of such subordinate unit during the Unit Testing.
A ‘Stub’ is a piece of software that works similar to a unit which is referenced by the Unit being tested, but it is much simpler that the actual unit. A Stub works as a ‘Stand-in’ for the subordinate unit and provides the minimum required behavior for that unit. A Stub is a dummy procedure, module or unit that stands in for an unfinished portion of a system.
Four basic types of Stubs for Top-Down Testing are:
- Display a trace message
- Display parameter value(s)
- Return a value from a table
- Return table value selected by parameter
A stub is a computer program which is used as a substitute for the body of a software module that is or will be defined elsewhere or a dummy component or object used to simulate the behavior of a real component until that component has been developed.
For example, if the movefighter method has not been written yet, a stub such as the one below might be used temporarily – which moves any player to position 1.
public void moveFighter(Fighter player, int LocationX, int LocationY)
{fighter.setPosition(1);}
Ultimately, the dummy method would be completed with the proper program logic. However, developing the stub allows the programmer to call a method in the code being developed, even if the method does not yet have the desired behavior.
Programmer needs to create such ‘Drivers’ and ‘Stubs’ for carrying out Unit Testing.
Both the Driver and the Stub are kept at a minimum level of complexity, so that they do not induce any errors while testing the Unit in question.
Stubs and drivers are often viewed as throwaway code. However, they do not have to be thrown away: Stubs can be "filled in" to form the actual method. Drivers can become automated test cases.
Example - For Unit Testing of ‘Sales Order Printing’ program, a ‘Driver’ program will have the code which will create Sales Order records using hardcoded data and then call ‘Sales Order Printing’ program. Suppose this printing program uses another unit which calculates Sales discounts by some complex calculations. Then call to this unit will be replaced by a ‘Stub’, which will simply return fix discount data.
Primary Key: identifies a row within a relational database and is used for indexing.
1. Primary key is an Identifier.
2. Used for indexing in RDBMS
3. Each row must have a UNIQUE primary key to properly represent the row as one entity.
4. when a user requests to view a record, the db tracks the record by its UPK( UNIQUE primary key)
1. Matches between foreign key and primary key is important because they represent references from one relation to another.
2. And establish the connections among these relations.
3. If an attribute in one relation/table has value matching the primary key in another table and there is a relationship set up between the two of them.....the attribute/column is called foreign key
component of a knowledge based system (KBS):
Knowledge base
Inference Engine
Interface between the user and the system
Procedural code in a procedural language implies sequential execution of instructions based on the von Neumann architecture of a CPU, Memory, and Input/Output device.
Variables are part of the sets of instructions used to solve a particular problem and, thus, the data are not separate from the statements. Such languages have control statements such as goto, ifƒthenƒelse and so on. The program execution is iterative and corresponds to a sequence of state changes in a state machine.
Knowledge base, refers to the rules and facts of the particular problem domain.
The inference engine, takes the inputs to the KBS and uses the knowledge base to infer new facts and to solve the problem.
the interface between the user and the system through which the data are entered, displayed, and output.
In an expert system, the process of beginning with a possible solution and using the knowledge in the knowledge base to justify the solution based on the raw input data is called:
Backward chaining
Backward chaining is generally used when there are a large number of possible solutions relative to the number of inputs.
forward chaining, is the reasoning approach that can be used when there is a small number of solutions relative to the number of inputs. The input data is used to reason forwardŽ to prove that one of the possible solutions in a small solution set is the correct one.
Blackboard, is an expert system reasoning methodology in which a solution is generated by the use of a virtual blackboardŽ wherein information or potential solutions are placed on the blackboard by a plurality of individuals or expert knowledge sources. As more information is placed on the blackboard in an iterative process, a solution is generated.
An off-the-shelf software package that implements an inference engine, a mechanism for entering knowledge, a user interface, and a system to provide explanations of the reasoning used to generate a solution is called:
a. An expert system shell
An expert system shell provides the fundamental building blocks of an expert system and supports the entering of domain knowledge. Thus, for an application that is not complex and does not require the custom development of the components of an expert system, an expert system shell is a useful tool that will save development time.
An expert system shell provides the fundamental building blocks of an expert system and supports the entering of domain knowledge.Thus, for an application that is not complex and does not require the custom development of the components of an expert system, an expert system shell is a useful tool that will save development time.
A neural network is another type of artificial intelligence system that uses the neurons of the brain as a model and solves problems using nonlinear pattern-matching techniques and learningŽ approaches.
A knowledge acquisition system
means of identifying and acquiring the knowledge to be entered into the knowledge base..
In simple terms, it is trying to determine how an expert thinks when developing a solution to a problem
key professional or professionals are required to develop an expert system:
Knowledge engineer and domain expert
The knowledge engineer usually has a computer-related and expert system background, but does not have the knowledge of the specific discipline or domain being addressed by the expert system.
For example, the expert system being developed may be a medical diagnostic system requiring input from diagnostic specialists and other types of physicians. These individuals are the domain experts.
It is the job of the knowledge engineer to elicit the critical knowledge from the domain expert and incorporate it into the expert system knowledge base.
An expert system that has rules of the form If w is low and x is high then y is intermediate,Ž where w and x are input variables and y is the output variable, is called a:
Fuzzy expert system
A fuzzy expert system is an expert system that uses fuzzy membership functions and rules, instead of Boolean logic, to reason about data.
Thus, fuzzy variables can have an approximate range of values instead of the binary True or False used in conventional expert systems.
When it is desired to convert the fuzzy output to a single value, defuzzification is used.
One approach to defuzzification is the CENTROID method:
With this method, a value of the output variable is computed by finding the variable value of the center of gravity of the membership function for the fuzzy output value.
Subject-oriented, integrated, time-variant, non-volatile collection of data in support of managements decision-making processŽ:
Data warehouse
This definition of a data warehouse is that of Bill Inmon, a pioneer in the field. To create a data warehouse, data is taken from an operational database, redundancies are removed, and the data is cleaned upŽ in general. This activity is referred to as normalizing the data.
Then the data is placed into a relational database and can be analyzed using On-Line Analytical Processing (OLAP) and statistical modeling tool.
The data warehouse can be used as a Decision Support System (DSS), for example, by performing a time series analysis of the data. The data in the data warehouse must be maintained to ensure that it is timely and valid.
The term data scrubbing refers to maintenance of the data warehouse by deleting information that is unreliable or no longer relevant.
data mart, is a database that is comprised of data or relations that have been extracted from the data warehouse. Information in the data mart is usually of interest to a particular group of people.
For example, a data mart may be developed for all health care-related data. (specific purpose)
The process of analyzing large data sets in a data warehouse to find non-obvious patterns is called:
The equation Z = f [ wn in ], where Z is the output, wn are weighting functions, and in is a set of inputs describes:
An artificial neural network (ANN)
Each input, in , is multiplied by a weight, wn , and these products are fed into a summation transfer function, , that generates an output, Z.
Most neural networks have multiple layers of summation and weighting functions, whose interconnections can also be changed.
There are a number of different learning paradigms for neural networks, including reinforcement learning and back propagation
In reinforcement learning a training set of inputs is provided to the ANN along with a measure of how close the network is coming to a solution. Then, the weights and connections are readjusted.
In back propagation, information is fed back inside the neural network from the output and is used by the ANN to make weight and connection adjustments.
A database that comprises tools to support the analysis, design, and development of software and support good software engineering practices is called a:
Data dictionary (middleware)
Computer Aided Software Engineering (CASE) tools and an Integrated Project Support Environment (IPSE) are terms used to describe similar software engineering support environments.
data model, is a basic system of constructs used in describing reality,Ž
DBMS: is a system that supports the creation, use, and administration of a database system.
Data type dictionary, refers to a collection of items on which certain operations, such as insert, delete, and search, are to be performed.
This arrangement of items is in contrast to a priority queue, in which the collection of items is arranged in order of priority and the relevant operations to be performed are insert, find-max, and delete-max.
Another type of artificial intelligence technology involves genetic algorithms. Genetic algorithms are part of the general class known as: Evolutionary computing
Evolutionary computing uses the Darwinian principles of survival of the fittest, mutation, and the adaptation of successive generations of populations to their environment. The genetic algorithm implements this process through iteration of generations of a constant-size population of items or individuals. Each individual is characterized by a finite string of symbols called genomes.
The genomes are used to represent possible solutions to a problem in a fixed search space.
For example, if the fixed population of the first generation of individuals consists of random binary numbers, and the problem is to find the minimum binary number that can be represented by an individual, each binary number is assigned a fitness value based on the individual is binary number value. The smaller the binary number represented by a parent individual, the higher level of fitness that is assigned to it. Through cross breeding among the numbers (known as crossover), mutations of the numbers, and pairing of numbers with high fitness ratings, the smallest value that can be represented by the number of bits in the binary number will emerge in later generations
Object Request Architecture (ORA) is a high-level framework for a distributed environment. It consists of four components:
a. Object Request Brokers (ORBs)
b. Object Services
c. Application Objects
The ORA is a product of the Object Management Group (OMG), which is a nonprofit consortium in Framingham, Massachusetts that was put together in 1989 to promote the use of object technology in distributed computing systems.
(www.omg.org)
1. ORB is the fundamental building block of ORA and manages the communications between the ORA entities.
2. The purpose of the ORB is to support the interaction of objects in heterogeneous, distributed environments.
3. The objects may be on different types of computing platforms.
Object Services, supports the ORB in creating and tracking objects as well as performing access control functions.
Application Objects Common Facilities support the end user and use the system services to perform their functions.
A standard that uses the Object Request Broker (ORB) to implement exchanges among objects in a heterogeneous, distributed environment is called:
A Common Object Request Broker Architecture (CORBA)
OMG Object Model provides standard means for describing the externally visible characteristics of objects.
IDL, is a standard interface language that is used by clients to request services from objects.
Another model that allows two software components to communicate with each other independent of their platforms operating systems and languages of implementation is:
Common Object Model (COM)
As in the object-oriented paradigm, COM works with encapsulated objects. Communications with a COM object are through an interface contract between an object and its clients that defines the functions that are available in the object and the behavior of the object when the functions are called.
Sandbox, is an access control-based protection mechanism. It is commonly applied to restrict the access rights of mobile code that is downloaded from a Web site as an applet. The code is set up to run in a sandboxŽ that blocks its access to the local workstations hard disk, thus preventing the code from malicious activity. The sandbox is usually interpreted by a virtual machine such as the Java Virtual Machine.
A distributed object model that has similarities to the Common Object Request Broker Architecture (CORBA) is:
Distributed Component Object Model (DCOM)
DCOM is the distributed version of COM that supports remote objects as if the objects reside in the clients address space. ACOM client can access a COM object through the use of a pointer to one of the objects interfaces and, then, invoking methods through that pointer.
Characteristic of a client in the client/server model:
a. Extensive user interface
b. May be diskless
c. Data entry screens
In the client/server model, the server is the data storage resource and is responsible for data backups and protection/maintenance of the database.
A client/server implementation approach in which any platform may act as a client or server or both is called:
Peer-to-peer
a workstation or PC uses terminal emulation software and a client application program to receive data from a host machine.
API defines how the client and server appear to each other and supports the exchange of information without either entity
knowing the details of a particular resource that is accessed using the API. One example is the Generalized Security Application Programming Interface (GSAPI) that applications can use to access security services.
GUI approach, is similar to the API implementation and employs a user interface such as SQL to access a server database.
characteristic of a distributed data processing (DDP) approach:
a. Consists of multiple processing locations that can provide alternatives for computing in the event of a site becoming inoperative.
b. Distances from user to processing resource are transparent to the user.
c. Data stored at multiple, geographically separate locations is easily available to the user.
d. Security is lowered because of networked systems.
A database management system (DBMS) is useful in situations where:
Rapid development of applications is required and pre-programmed functions can be used to provide those applications along with other support features such as security, error recovery, and access control.
A DBMS is called for when the required skilled programming resources are not available, information to be stored and accessed is common to many organizational business units, the processing requirements change frequently and timely responses are required for queries on the data.
Hierarchical databases are the oldest.
To access a data entity within a hierarchical database, it requires the knowledge of which branch to start with and which route to take through each layer until the data is reached.
Relational databases use INDEXES to search procedure.
Note: Links cannot be created between different branches and leaves on different layers.
Data Dictionary: contains data elements, their description and their relationships. It also contains info like data format, usage and origin.
Mechanism that ensures that a failed transaction or system failure returns the subject to a meaningful point in a process. .....checkpoint
Component of Expert system that matches facts against patterns and determines which rules are acceptable based on algorithms(that dictate system behavior) ....Inference engine
OS allows sequential use of object without refreshing it what issue can arise: Disclosure of residual data.
Network Based database Model:
It is a flexible way of representing objects and their relationships.
Its distinguishing feature is the schema; viewed as a graph in which objects are nodes and relationships are arcs.
It is not restricted to hierarchy or lattice. NBDB is base upon hierarchical data model but not restricted to it.
Instead of being constrained of how to go from one branch to another and from one parent to a child to find a data element. NBDB allows each data element to have multiple parent and child records.
This gives NBDS a redundant network like structure instead of a strict tree like structure.
A network model forms a structure similar to mesh topology for sake of redundancy. and allows quick retrieval of data compared to hierarchical model.
OODB vs RDBMS
1. Have procedures RDBMS need application to have data procedure
2. OODB are more dynamic.
3. OODB handle audio, video, document
4. OODB has classes to define attributes and procedures of its objects
CC uses PP as a specific security solution and these are reusable.
Network and Network Security(Network devices and configurations) ----RED book--ITSEC-- TNI
Operating system----Orange book-- US--TCSEC--DOD
Using automated Tools and mechanism to reduce cost and streamline the process ....CASE (Computer aided software engineering)
Foreign key - attribute of one column of a table related to primary key of another table.
Schema -- describes structure of database.
Data dictionary - central repository of data elements and their relations.
OLE DB: Object Linked and embedded database:
1. It separates data components that run as a middleware on client or server.
2. It provides a low-level interface to link information across different databases, and provides access to data no matter where it is located or how it is formatted.
3. OLE DB is replaced by ODBC (Open Database Connectivity), ODBC supports a wide variety of non-relational databases and spreadsheets that do not necessarily implement SQL.
4. A set of COM(component object model, MS)-based provide applications with uniform access to data stored in diverse data sources.
5. OLE DB (because it is COM based) is limited to use by MS windows-based client tool..
6. It allows different applications to access different types of and source of data.
OLE DB sources, the CommandType property describes the value of the CommandText property.
ODBC sources, the CommandText property functions exactly like the SQL property, and setting the property causes the data to be refreshed
[OLE DB and ODBC are APIs that provide access to a range of data sources. Microsoft designed ODBC to access SQL data and OLE DB to access any type of data in a COM environment. Many people don't entirely understand the factors that led Microsoft to implement OLE DB. Others overestimate the current role of OLE DB in the corporate and Web-development environments.]
[architecture of ODBC and OLE DB. Both rely on specialized components (drivers in ODBC and providers in OLE DB) that connect to the data source. Within ODBC, a driver usually acts as a proxy component, passing in SQL commands to the DBMS and returning result sets. An OLE
DB provider accepts data in any query language it supports (not only and not necessarily SQL) and returns recordsets. A data provider encapsulating a DBMS (ODBC) is limited to passing SQL commands to the underlying database server. A data provider that renders a nonrelational data store (e.g., an email store) accomplishes the additional task of creating the recordset and populating it with the data. Such a provider might support a query language that is simpler than SQL. For example, to return email from a customer, the provider needs to know only the name of the sender. This type of command]
ADO:
ActiveX Data Objects:
Characteristics of ADO:
1. It is a high level data access programming interface to an underlying data access technology (OLE DB)
2. It is a set of COM objects for accessing data sources and not just database access.
3. It allows a developer to write program that access data without knowing how the database is implemented.
4, SQL commands are not required to access a database when using ADO.
Row/Tuple/record/ cardinality
column/ Attribute
Schema of a Database:
1. Schema of a db is system is structure described in a formal language(supported by DBMS).
2. In relational db, schema defines: tables, fields, relationships, views, indexes, packages, procedures, functions, functions, queues, triggers, types, sequences, materialized views, synonyms, db links, directories, Java, XML, schemas, are stored in data dictionary.
Note: Schema data = table, field.......
The best programmers use high cohesion because different modules(units) need to pass data and communicate(they can't be totally cohesive ) and low coupling because lower the coupling better the software design because it promotes module independence.
Software Testing Approaches:
1. Top down Testing: In this approach testing is conducted from main module to sub module. if the sub module is not developed a temporary program called STUB is used for simulate the submodule.
Advantages:
- Advantageous if major flaws occur toward the top of the program.
- Once the I/O functions are added, representation of test cases is easier.
- Early skeletal Program allows demonstrations and boosts morale.
Disadvantages:
- Stub modules must be produced
- Stub Modules are often more complicated than they first appear to be.
- Before the I/O functions are added, representation of test cases in stubs can be difficult.
- Test conditions ma be impossible, or very difficult, to create.
- Observation of test output is more difficult.
- Allows one to think that design and testing can be overlapped.
- Induces one to defer completion of the testing of certain modules.
Bottom up testing: In this approach testing is conducted from sub module to main module, if the main module is not developed a temporary program called DRIVERS is used to simulate the main module.
Advantages:
- Advantageous if major flaws occur toward the bottom of the program.
- Test conditions are easier to create.
- Observation of test results is easier.
Disadvantages:
- Driver Modules must be produced.
- The program as an entity does not exist until the last module is added.
Stubs and Drivers
It is always a good idea to develop and test software in "pieces". But, it may seem impossible because it is hard to imagine how you can test one "piece" if the other "pieces" that it uses have not yet been developed (and vice versa).
A software application is made up of a number of ‘Units’, where output of one ‘Unit’ goes as an ‘Input’ of another Unit. e.g. A ‘Sales Order Printing’ program takes a ‘Sales Order’ as an input, which is actually an output of ‘Sales Order Creation’ program.
Due to such interfaces, independent testing of a Unit becomes impossible. But that is what we want to do; we want to test a Unit in isolation! So here we use ‘Stub’ and ‘Driver.
A ‘Driver’ is a piece of software that drives (invokes) the Unit being tested. A driver creates necessary ‘Inputs’ required for the Unit and then invokes the Unit.
Driver passes test cases to another piece of code. Test Harness or a test driver is supporting code and data used to provide an environment for testing part of a system in isolation. It can be called as as a software module which is used to invoke a module under test and provide test inputs, control and, monitor execution, and report test results or most simplistically a line of code that calls a method and passes that method a value.
For example, if you wanted to move a fighter on the game, the driver code would bemoveFighter(Fighter, LocationX, LocationY);
This driver code would likely be called from the main method. A white-box test case would execute this driver line of code and check "fighter.getPosition()" to make sure the player is now on the expected cell on the board.
A Unit may reference another Unit in its logic. A ‘Stub’ takes place of such subordinate unit during the Unit Testing.
A ‘Stub’ is a piece of software that works similar to a unit which is referenced by the Unit being tested, but it is much simpler that the actual unit. A Stub works as a ‘Stand-in’ for the subordinate unit and provides the minimum required behavior for that unit. A Stub is a dummy procedure, module or unit that stands in for an unfinished portion of a system.
Four basic types of Stubs for Top-Down Testing are:
- Display a trace message
- Display parameter value(s)
- Return a value from a table
- Return table value selected by parameter
A stub is a computer program which is used as a substitute for the body of a software module that is or will be defined elsewhere or a dummy component or object used to simulate the behavior of a real component until that component has been developed.
For example, if the movefighter method has not been written yet, a stub such as the one below might be used temporarily – which moves any player to position 1.
public void moveFighter(Fighter player, int LocationX, int LocationY)
{fighter.setPosition(1);}
Ultimately, the dummy method would be completed with the proper program logic. However, developing the stub allows the programmer to call a method in the code being developed, even if the method does not yet have the desired behavior.
Programmer needs to create such ‘Drivers’ and ‘Stubs’ for carrying out Unit Testing.
Both the Driver and the Stub are kept at a minimum level of complexity, so that they do not induce any errors while testing the Unit in question.
Stubs and drivers are often viewed as throwaway code. However, they do not have to be thrown away: Stubs can be "filled in" to form the actual method. Drivers can become automated test cases.
Example - For Unit Testing of ‘Sales Order Printing’ program, a ‘Driver’ program will have the code which will create Sales Order records using hardcoded data and then call ‘Sales Order Printing’ program. Suppose this printing program uses another unit which calculates Sales discounts by some complex calculations. Then call to this unit will be replaced by a ‘Stub’, which will simply return fix discount data.
Primary Key: identifies a row within a relational database and is used for indexing.
1. Primary key is an Identifier.
2. Used for indexing in RDBMS
3. Each row must have a UNIQUE primary key to properly represent the row as one entity.
4. when a user requests to view a record, the db tracks the record by its UPK( UNIQUE primary key)
1. Matches between foreign key and primary key is important because they represent references from one relation to another.
2. And establish the connections among these relations.
3. If an attribute in one relation/table has value matching the primary key in another table and there is a relationship set up between the two of them.....the attribute/column is called foreign key
component of a knowledge based system (KBS):
Knowledge base
Inference Engine
Interface between the user and the system
Procedural code in a procedural language implies sequential execution of instructions based on the von Neumann architecture of a CPU, Memory, and Input/Output device.
Variables are part of the sets of instructions used to solve a particular problem and, thus, the data are not separate from the statements. Such languages have control statements such as goto, ifƒthenƒelse and so on. The program execution is iterative and corresponds to a sequence of state changes in a state machine.
Knowledge base, refers to the rules and facts of the particular problem domain.
The inference engine, takes the inputs to the KBS and uses the knowledge base to infer new facts and to solve the problem.
the interface between the user and the system through which the data are entered, displayed, and output.
In an expert system, the process of beginning with a possible solution and using the knowledge in the knowledge base to justify the solution based on the raw input data is called:
Backward chaining
Backward chaining is generally used when there are a large number of possible solutions relative to the number of inputs.
forward chaining, is the reasoning approach that can be used when there is a small number of solutions relative to the number of inputs. The input data is used to reason forwardŽ to prove that one of the possible solutions in a small solution set is the correct one.
Blackboard, is an expert system reasoning methodology in which a solution is generated by the use of a virtual blackboardŽ wherein information or potential solutions are placed on the blackboard by a plurality of individuals or expert knowledge sources. As more information is placed on the blackboard in an iterative process, a solution is generated.
An off-the-shelf software package that implements an inference engine, a mechanism for entering knowledge, a user interface, and a system to provide explanations of the reasoning used to generate a solution is called:
a. An expert system shell
An expert system shell provides the fundamental building blocks of an expert system and supports the entering of domain knowledge. Thus, for an application that is not complex and does not require the custom development of the components of an expert system, an expert system shell is a useful tool that will save development time.
An expert system shell provides the fundamental building blocks of an expert system and supports the entering of domain knowledge.Thus, for an application that is not complex and does not require the custom development of the components of an expert system, an expert system shell is a useful tool that will save development time.
A neural network is another type of artificial intelligence system that uses the neurons of the brain as a model and solves problems using nonlinear pattern-matching techniques and learningŽ approaches.
A knowledge acquisition system
means of identifying and acquiring the knowledge to be entered into the knowledge base..
In simple terms, it is trying to determine how an expert thinks when developing a solution to a problem
key professional or professionals are required to develop an expert system:
Knowledge engineer and domain expert
The knowledge engineer usually has a computer-related and expert system background, but does not have the knowledge of the specific discipline or domain being addressed by the expert system.
For example, the expert system being developed may be a medical diagnostic system requiring input from diagnostic specialists and other types of physicians. These individuals are the domain experts.
It is the job of the knowledge engineer to elicit the critical knowledge from the domain expert and incorporate it into the expert system knowledge base.
An expert system that has rules of the form If w is low and x is high then y is intermediate,Ž where w and x are input variables and y is the output variable, is called a:
Fuzzy expert system
A fuzzy expert system is an expert system that uses fuzzy membership functions and rules, instead of Boolean logic, to reason about data.
Thus, fuzzy variables can have an approximate range of values instead of the binary True or False used in conventional expert systems.
When it is desired to convert the fuzzy output to a single value, defuzzification is used.
One approach to defuzzification is the CENTROID method:
With this method, a value of the output variable is computed by finding the variable value of the center of gravity of the membership function for the fuzzy output value.
Subject-oriented, integrated, time-variant, non-volatile collection of data in support of managements decision-making processŽ:
Data warehouse
This definition of a data warehouse is that of Bill Inmon, a pioneer in the field. To create a data warehouse, data is taken from an operational database, redundancies are removed, and the data is cleaned upŽ in general. This activity is referred to as normalizing the data.
Then the data is placed into a relational database and can be analyzed using On-Line Analytical Processing (OLAP) and statistical modeling tool.
The data warehouse can be used as a Decision Support System (DSS), for example, by performing a time series analysis of the data. The data in the data warehouse must be maintained to ensure that it is timely and valid.
The term data scrubbing refers to maintenance of the data warehouse by deleting information that is unreliable or no longer relevant.
data mart, is a database that is comprised of data or relations that have been extracted from the data warehouse. Information in the data mart is usually of interest to a particular group of people.
For example, a data mart may be developed for all health care-related data. (specific purpose)
The process of analyzing large data sets in a data warehouse to find non-obvious patterns is called:
The equation Z = f [ wn in ], where Z is the output, wn are weighting functions, and in is a set of inputs describes:
An artificial neural network (ANN)
Each input, in , is multiplied by a weight, wn , and these products are fed into a summation transfer function, , that generates an output, Z.
Most neural networks have multiple layers of summation and weighting functions, whose interconnections can also be changed.
There are a number of different learning paradigms for neural networks, including reinforcement learning and back propagation
In reinforcement learning a training set of inputs is provided to the ANN along with a measure of how close the network is coming to a solution. Then, the weights and connections are readjusted.
In back propagation, information is fed back inside the neural network from the output and is used by the ANN to make weight and connection adjustments.
A database that comprises tools to support the analysis, design, and development of software and support good software engineering practices is called a:
Data dictionary (middleware)
Computer Aided Software Engineering (CASE) tools and an Integrated Project Support Environment (IPSE) are terms used to describe similar software engineering support environments.
data model, is a basic system of constructs used in describing reality,Ž
DBMS: is a system that supports the creation, use, and administration of a database system.
Data type dictionary, refers to a collection of items on which certain operations, such as insert, delete, and search, are to be performed.
This arrangement of items is in contrast to a priority queue, in which the collection of items is arranged in order of priority and the relevant operations to be performed are insert, find-max, and delete-max.
Another type of artificial intelligence technology involves genetic algorithms. Genetic algorithms are part of the general class known as: Evolutionary computing
Evolutionary computing uses the Darwinian principles of survival of the fittest, mutation, and the adaptation of successive generations of populations to their environment. The genetic algorithm implements this process through iteration of generations of a constant-size population of items or individuals. Each individual is characterized by a finite string of symbols called genomes.
The genomes are used to represent possible solutions to a problem in a fixed search space.
For example, if the fixed population of the first generation of individuals consists of random binary numbers, and the problem is to find the minimum binary number that can be represented by an individual, each binary number is assigned a fitness value based on the individual is binary number value. The smaller the binary number represented by a parent individual, the higher level of fitness that is assigned to it. Through cross breeding among the numbers (known as crossover), mutations of the numbers, and pairing of numbers with high fitness ratings, the smallest value that can be represented by the number of bits in the binary number will emerge in later generations
Object Request Architecture (ORA) is a high-level framework for a distributed environment. It consists of four components:
a. Object Request Brokers (ORBs)
b. Object Services
c. Application Objects
The ORA is a product of the Object Management Group (OMG), which is a nonprofit consortium in Framingham, Massachusetts that was put together in 1989 to promote the use of object technology in distributed computing systems.
(www.omg.org)
1. ORB is the fundamental building block of ORA and manages the communications between the ORA entities.
2. The purpose of the ORB is to support the interaction of objects in heterogeneous, distributed environments.
3. The objects may be on different types of computing platforms.
Object Services, supports the ORB in creating and tracking objects as well as performing access control functions.
Application Objects Common Facilities support the end user and use the system services to perform their functions.
A standard that uses the Object Request Broker (ORB) to implement exchanges among objects in a heterogeneous, distributed environment is called:
A Common Object Request Broker Architecture (CORBA)
OMG Object Model provides standard means for describing the externally visible characteristics of objects.
IDL, is a standard interface language that is used by clients to request services from objects.
Another model that allows two software components to communicate with each other independent of their platforms operating systems and languages of implementation is:
Common Object Model (COM)
As in the object-oriented paradigm, COM works with encapsulated objects. Communications with a COM object are through an interface contract between an object and its clients that defines the functions that are available in the object and the behavior of the object when the functions are called.
Sandbox, is an access control-based protection mechanism. It is commonly applied to restrict the access rights of mobile code that is downloaded from a Web site as an applet. The code is set up to run in a sandboxŽ that blocks its access to the local workstations hard disk, thus preventing the code from malicious activity. The sandbox is usually interpreted by a virtual machine such as the Java Virtual Machine.
A distributed object model that has similarities to the Common Object Request Broker Architecture (CORBA) is:
Distributed Component Object Model (DCOM)
DCOM is the distributed version of COM that supports remote objects as if the objects reside in the clients address space. ACOM client can access a COM object through the use of a pointer to one of the objects interfaces and, then, invoking methods through that pointer.
Characteristic of a client in the client/server model:
a. Extensive user interface
b. May be diskless
c. Data entry screens
In the client/server model, the server is the data storage resource and is responsible for data backups and protection/maintenance of the database.
A client/server implementation approach in which any platform may act as a client or server or both is called:
Peer-to-peer
a workstation or PC uses terminal emulation software and a client application program to receive data from a host machine.
API defines how the client and server appear to each other and supports the exchange of information without either entity
knowing the details of a particular resource that is accessed using the API. One example is the Generalized Security Application Programming Interface (GSAPI) that applications can use to access security services.
GUI approach, is similar to the API implementation and employs a user interface such as SQL to access a server database.
characteristic of a distributed data processing (DDP) approach:
a. Consists of multiple processing locations that can provide alternatives for computing in the event of a site becoming inoperative.
b. Distances from user to processing resource are transparent to the user.
c. Data stored at multiple, geographically separate locations is easily available to the user.
d. Security is lowered because of networked systems.
A database management system (DBMS) is useful in situations where:
Rapid development of applications is required and pre-programmed functions can be used to provide those applications along with other support features such as security, error recovery, and access control.
A DBMS is called for when the required skilled programming resources are not available, information to be stored and accessed is common to many organizational business units, the processing requirements change frequently and timely responses are required for queries on the data.
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