mobile computing database
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PowerPoint Presentation
Mobile Computing
Lesson 01 DATABASE1
Computations
Require data
Better to organise this data in a database
Database enables raising queries, datatransactions, and the retrieval of therequired section of data during acomputation
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Database
A collection of systematically storedrecords or information
Is not just arbitrarily stored data withoutany logic
Stores data in a particular logical
manner, for example, as lookup tables
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Lookup table
A database which stores information intabular form
Table structurethe first column areference for looking into the data
Subsequent column or columns containthe data
The referencekey to the data-values
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Tags based database
Another logical structure
A tag is also the key to the data-values
For example, contact: 1 John, 2 Lucy.and address: 1 ABC Street, 2 DEFStreet.
contact and address tags in thedatabase
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Business ( transactions) between theapplication software and database
Computational actions connecting to adatabase
Using the database for querying for arecord
Deleting a specific set of records
Modifications of records
insertions into the records and
Appending of the records
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Transaction command
Command which is sent for retrieving thedata from the database, embodies thelogic used for obtaining (and storing) thedata
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Data stored in databases
Follows a logic
Business logic indicates the logical wayin which transactions (business) carriedout
Between two ends, for example, betweendatabase-client (application) and
database-server or between an API anda database
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API (application program interface)
A section of a program used to run anapplication (software)
API may run instructions to retrieve aqueried record from a database
The API may also issue outputs orqueries and commands to anotherprogram and receive the inputs fromanother program during a program-run
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API at mobile device sending queries andretrieving data from local database
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Transactions involving databases
Establishing connection between APIand database
Updating data records by inserting,adding, replacing, or deleting
Querying for records
Terminating the connection between theAPI and the database
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Implicit Business Logic
Business logic indicates the logical
manner, flow, or pattern, in whichbusiness (or transactions) may becarried out with a database
Implicit business logic The structureand components of the database itselfdefine, which is used in retrieving (ormodifying) data from the database
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Implicit Business Logic
The logic of transactions (business logic)implicit when it comes from within thedatabase
No external definition required for thebusiness logic to function
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Example of Implicit Business Logic
Telephone Directory in which the firstword of each line is structured
alphabetically
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The telephone directory
Names and telephone numbers arrangedalphabetically shows implicit businesslogic
Names and telephone numbers
structured in rows with each row havinga name and the corresponding addressand telephone number
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Search directory in an XML database
Arranged alphabetically
Database designed using XML uses a tagas a key
The key enables business (transaction forretrieving, deleting, inserting, or modifyingdata)
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Search directory in an XML database
Raj Kamal
ABC Street, .
9876543210
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Search directory in an XML database
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Explicit business logic
Stored queries and procedures definethe logic
A transaction (business) between the
API and the database uses an explicitlydefined query
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Example of Explicit business logic
If Structure = most recently added entrylist Content_Type = English
English_Records, flight origin = Frankfurt,airline = Lufthansa, present time = 0800hrs and status = Not arrived thenGet_Records
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Example of Explicit business logic
Another query for business can be
If flight origin = Frankfurt, airline =
Lufthansa, present time = 0800 hrs andstatus = arrived then Delete_Records
English_Records a section of thedatabase having English contents
Get_Records and Delete_Records twoprocedures that carry the transactions
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Connectivity Protocol
An API that has predefined methods tohandle the various data access functions
Defines ways to connect to and access adatabase and methods for sending queriesand updating or retrieving databaserecords
Connects a client or server to thedatabase
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Connectivity Protocols
Describes the set of permitted commands,transaction methods, and the order inwhich commands are interchangedbetween the API and the database at theserver or the client
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Connectivity Protocols
Using the connectivity protocol API, aprogram issues commands
Access a database and query in order toselect and retrieve queried record(s) fromthe database
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Examples of connectivity protocols
Java database connectivity (JDBC)
Open database connectivity (ODBC)
Simple object access protocol (SOAP)
Connect the server to the database
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Relational Databases
Defined as a database structured inaccordance with the relational model
The relational model of data organizationhelps the database designer to create aconsistent and logical representation ofinformation
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The relational model
Follows a relational logic which means thatit is assumed that all data can be
represented as n-ary (binary means n = 2,tertiary means n = 3,...) relations
An n-ary relation is a subset of theCartesian products of n-sets
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Relational database
Entails that it is always possible to
mathematically model the relations
between the data records and get the
answers to the relational equations for thequeries
The answers are as in two-valuedpredicate logic
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Two-valued predicate logic
Means that there are only two possibleresults on evaluation, for each
propositiontrue or false and no third
result, for example, null or unknown, ispossible
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IBM DB2 Everyplace (DB2e)
A relational database engine
Needs a memory of about 100 kB
Designed to reside at the device
Supports databases of sizes up to 120 MB
An enterprise server employing DB2e
delivers and synchronizes the local copiesof data contents at mobile devices
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DB2e based Synchronization
DB2e synchronizes with DB2 databases atthe synchronization, application, orenterprise server
Means that if a data record is modified atthe server then the copy of that record atthe client device also changes accordingly
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API at mobile device retrieving datafrom database using DB2e
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Summary
Database a collection of systematicallystored records or information
Business logic indicates the logical wayin which transactions (business) carriedout between two ends
XML database
Implicit Business Logic
Explicit business logic for Stored queries
and procedures
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Summary
Transactions involving databases are
(a) establishing connection (b) updatingdata records by inserting, adding,replacing, or deleting, (c) querying and
(d) terminating the connection
Connectivity protocol
Relational databases
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Summary
IBM DB2e EveryPlace for retrievingdatabase records and querying fromDB2e server
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End of Lesson DATABASE37
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