Data Synchronization in Mobile Computing Systems Lesson 08 SyncML Language Features

Transcription

1 Data Synchronization in Mobile Computing Systems Lesson 08 SyncML Language Features Oxford University Press All rights reserved. 1

2 A mobile computing system Consists of (i) mobile device, (ii) personal area computer in a WPAN, a computer connected by WLAN, or Internet, (iii) nearby devices, for example, printer, and (iv) mobile service provider connected by wireless Oxford University Press All rights reserved. 2

3 A mobile computing system In general, each of the devices can use different platforms One device may use Symbian OS, another Palm OS, and the computer on WLAN Windows OS Also, each one can use different languages For example, a device may use Java and the computer C/C++ Oxford University Press All rights reserved. 3

4 Use of SyncML Language Database connector for SyncML-based mobile application synchronizes data at the device with any relational database SyncML-based software synchronizes data for PIM ( , calendar, memo, tasks-to-do list, or contacts list) Oxford University Press All rights reserved. 4

5 JCF (Jataayu client framework) A client framework to enable functioning of the software on different platforms Oxford University Press All rights reserved. 5

6 Use of SyncML client and SyncML engine APIs for PIM, , and customized device application can deploy SyncML client and SyncML engine SyncML server for sending response to the requests from the other node, computer, or device Sends the messages which accompany the data and the operational results as per the messages Oxford University Press All rights reserved. 6

7 SyncML (Synchronization Markup Language) A data synchronization language based on XML (Extensible Markup Language) In other words, it is a markup language used for writing the codes for interfaces used for synchronization between the mobile devices and the server Oxford University Press All rights reserved. 7

8 XML Base of SyncML A language for marking up a given text with tags and attributes and it is extensively used in mobile computing Oxford University Press All rights reserved. 8

9 Example of XML codes <search_list> <!- - Contact information about contacts identified by first alphabet as R - - > <alp_name first_character = R > <contact_name> Raj Kamal <address> ABC Street,. </address> <telnumber> </telnumber> </contact_name> Oxford University Press All rights reserved. 9

10 Example of XML codes <contact_name> Raveena <address> XYZ Street,. </address> <telnumber> </telnumber> </contact_name> </alp_name> </search_list Oxford University Press All rights reserved. 10

11 Comments in XML Comments are not used in parsing (processing) of the codes. XML comments start with <!- - (less than sign,! sign and two dashes) and ends with - - > (two dashes before the greater than sign) Oxford University Press All rights reserved. 11

12 Start and last tags for writing the text of a search list in between the tags The start tag starts with < sign Followed by a tag name which is search_list in this case ends with > sign The last tag starts with <, followed by a slash sign, the same tag name as at the start, and > sign Oxford University Press All rights reserved. 12

13 Inner tag with attributes For example, alp_name with attribute specification first_character = R The coding format is < sign, tag name, tag attribute or attributes, > sign, followed by text associated with the given tag and attributes, < sign, slash sign, tag name and > sign Oxford University Press All rights reserved. 13

14 Data type definitions (DTD) file For an XML document, there is a data type definitions (DTD) file which specifies the rules For example, for the document given, it specifies that search_list is the root element and that contact_name contains the address and telephone number Oxford University Press All rights reserved. 14

15 XML A platform independent processing language This implies that it can be used for processing not only by Java but also by any other language Tags, attributes, and metadata formats in XML are standardized so that they can be universally interpreted on different platforms, machines, or networks Oxford University Press All rights reserved. 15

16 SyncML and Voice XML SyncML an open standard based on XML. It has revolutionized mobile application-development, services, and devices Voice XML another language based on XML and is used for communicating voice messages Oxford University Press All rights reserved. 16

17 SyncMLML based Information Exchange Between a client and server in form of an envelope representing a message Term message describes information A tag and its attributes define an envelope of a text message Each envelope has a header followed by body Oxford University Press All rights reserved. 17

18 SyncML Header and Body The header exists between header start and end tags The body which includes the commands is present between body start and end tags The envelope exchanged between client and server by request and response messages Oxford University Press All rights reserved. 18

19 SyncML Header and Body SyncML message has two components (a) a header which starts with the start tag <SyncHdr> and ends with the end tag </SyncHdr> and (b) a body which starts with <SyncBody> and ends with </SyncBody> Oxford University Press All rights reserved. 19

20 SyncHdr Consists of DTD, protocol, and data (message or session) identifications Includes target and source information Carries initialization information which is required before synchronization The initialization information enables device authentication and includes information on available device functions Oxford University Press All rights reserved. 20

21 Example of SyncML Header <SyncML> <SyncHdr> <VerDTD>1.0</VerDTD> <VerProto>SyncML/1.0</VerProto> <SessionID>session01</SessionID> <MsgID>message09</MsgID> <Target><LocURI> Oxford University Press All rights reserved. 21

22 Example of SyncML Header <!- - LocURI means local URI. URI means Universal Resource Identifier - - > <Source><LocURI>IMEI: </LocURI></Source> < - - IMEI is International Mobile Equipment Identity represented by a number - -> </SyncHdr> Oxford University Press All rights reserved. 22

23 Use of SyncBody <SyncBody> </SyncBody> </SyncML> Oxford University Press All rights reserved. 23

24 SyncML used between client and server The accompanying data (payload) is placed between a start tag and the corresponding last tag SyncML can be used between client and server for sending messages and data and for synchronization as it has standard defined tags, commands and protocol for exchange Oxford University Press All rights reserved. 24

25 Definition of the term Data store A term used in SyncML codes for persistent data storage It is also written as DataStore Refers to storage of data in a file system or database or in any other way in which persistency is maintained Oxford University Press All rights reserved. 25

26 Data store In the context of mobile devices, persistency means that the data remains intact till deleted even if the device power is interrupted Implies that a change in data during an operation is simultaneously stored and reflected at all related files in file system, database, or any other record Oxford University Press All rights reserved. 26

27 Example of DataStore Suppose a telephone number is stored in a mobile device The flash memory file stores it persistently and it is used in call operations Oxford University Press All rights reserved. 27

28 Example of DataStore When user modifies the telephone number in Contacts at PIM using an API, it is also stored and modified at the flash storage and will be available any time on next call When user deletes the telephone number in Contacts, only then the number looses persistency Oxford University Press All rights reserved. 28

29 Use of DataStore APIs, for example, PMI or , use a Data store mechanism For synchronizing data using different Data store mechanisms at the nodes (client, database, file system, or server), with each one, in general, using different platforms and languages, is a difficult task Oxford University Press All rights reserved. 29

30 SyncML Can be used for sending messages of the APIs and data using the Data store mechanism at both the client and server ends Oxford University Press All rights reserved. 30

31 Parsing of SyncML message A SyncML message from SyncML client or server is used after parsing the tags, attributes and the text A SyncML message parsed similar to an XML document For example, the search list an XML document, in Sample Oxford University Press All rights reserved. 31

32 Example of Using Parser The parser also able to retrieve the data for the contact name, telephone number, and address An API at the device or server can save the data using the Data store mechanism An API can use the data for synchronization with another API in personal area network or at server Oxford University Press All rights reserved. 32

33 Parse use by an API Assume that an API uses a parser and parses for contact names, then firstly the parser will parse for alphabet tag, then first character R As a result, the parser gets the contact names with first character as the alphabet R A parser program associated with PIM API can be used to get a list of contact names Oxford University Press All rights reserved. 33

34 Parser Using the document in Sample Code, an item in the list of items will be first line: Name Raj Kamal, second line: Address ABC Street,, and third line Phone Oxford University Press All rights reserved. 34

35 Sync ML Data Type Definitions SyncML, like XML, uses DTDs These include device information DTD, service information DTD, meta information DTD (for metadata), and main SyncML DTD Service information DTD represents the functional capabilities of the data objects supported by client or server Oxford University Press All rights reserved. 35

36 Two-way synchronization If a client supports vcard version 2.1 for two-way synchronization, the server must also have this capability; otherwise the synchronization session for the vcard data object cannot proceed Oxford University Press All rights reserved. 36

37 SyncML DTD Also exchanged with the message SyncML defines a universal data synchronization format DTD, which is exchanged with a SyncML message Oxford University Press All rights reserved. 37

38 Metadata in Data Type Definitions Metadata is information regarding the stored data or it is information about information Like XML document, the SyncML metadata is structured data that describes various characteristics of informationcarrying elements Oxford University Press All rights reserved. 38

39 Data store info Whether Data store mechanism is database-based or file-based Oxford University Press All rights reserved. 39

40 Device info Has information about the device capability for synchronization Device info consists of device type, model number, manufacturer, device hardware version specification, device software specification, and device capabilities for maintaining data copies and synchronization Oxford University Press All rights reserved. 40

41 Metadata Helps in discovering and locating data or in its assessment The metadata data helps in the identification or management of data in the subsequent text data in the document Metadata considered as information about data or as information about information Oxford University Press All rights reserved. 41

42 Open Standard Acceptability by OMA Initiative for universal acceptability of SyncML is a project of the Open Mobile Alliance (OMA) The OMA SyncML initiative came from IBM, Motorola, Nokia, Palm, Ericsson, Lotus, Starfish, and Psion Later many organizations joined Oxford University Press All rights reserved. 42

43 Summary SyncML is a standard XML based language for mobile application development Parsing similar to XML DataStore SyncML DTD Metadata Oxford University Press All rights reserved. 43

44 Summary Tags and attributes Envelope Header Body Oxford University Press All rights reserved. 44

45 End of Lesson 8 SyncML Language Features Oxford University Press All rights reserved. 45