Prerequisite
Knowledge
EPCC, University of Edinburgh
Neil Chue Hong
N.ChueHong@epcc.ed.ac.uk
OGSA-DAI Training Workshop - April 2003
Release: P2R2
Talk Outline
4Recap of terminology and assumed knowledge
– XML
• Schema, SOAP, WSDL, G-WSDL
• Tomcat, Axis
– Database
• SQL, JDBC, MySQL, DB2, XML:DB, XPath, XUpdate, Xindice
– Grid
• OGSI, OGSA, Globus Toolkit, GridFTP, …
4Tools and languages?
– Ant, Java, log4J
4Anything else…
2
OGSA-DAI Training Workshop, Release: P2R2
XML
XML Schema
4 Already had an introduction to XML
– Text based hence portable
– Mark-up facilitates machine processing
4 XML Schema overcome some of the limitations of DTDs
– Schemas are XML documents themselves
– Schemas express XML vocabularies and grammar/syntax that can be
used in XML documents
4 XML documents are
– Well formed if start and closing tags match
– Valid if they conform to an XML Schema
4 More information from
– http://www.w3.org/XML/Schema
4
OGSA-DAI Training Workshop, Release: P2R2
SOAP
4 SOAP is:
– a stateless,
– one-way message exchange paradigm
4 Applications can create more complex interaction
patterns:
– request/response,
– request/multiple
– responses, etc
4 Silent on:
–
–
–
–
5
the semantics of any application-specific data it conveys
the routing of SOAP messages,
reliable data transfer,
firewall traversal, etc.
OGSA-DAI Training Workshop, Release: P2R2
SOAP2
4Can operate over various transports:
– http
– ftp
– smtp, etc.
4Provides a framework to convey applicationspecific information in an extensible manner.
4Provides a full description of the required
actions taken by a SOAP node on receiving a
SOAP message.
4More information from
– http://www.w3.org/2000/xp/Group/
6
OGSA-DAI Training Workshop, Release: P2R2
WSDL
4 Used to describe interfaces to web services
4 Uses XML to do this and conforms to a WSDL XML
Schema
– Current W3C recommendation at version 1.1
4 Describes network services as a set of endpoints
operating on messages containing either
– document-oriented information or
– procedure-oriented information.
4 Operations and messages are described abstractly
4 Bound to a concrete network protocol and message
format to define an endpoint
4 Related concrete endpoints are combined into abstract
endpoints (services)
7
OGSA-DAI Training Workshop, Release: P2R2
WSDL (2)
4WSDL is extensible to allow description of
endpoints and their messages
– regardless of what message formats or network protocols are
used to communicate,
4However, WSDL is typically used in
conjunction with:
– SOAP 1.1
– HTTP GET/POST
– MIME
4More information from
– http://www.w3.org/TR/wsdl
8
OGSA-DAI Training Workshop, Release: P2R2
GWSDL
4There are deficiencies in WSDL 1.1
– Lack of Interface inheritance
• Needed for portTypes
– Lack of an open content model
• Needed for service data elements
4These features are in WSDL 1.2
– WSDL 1.2 only in draft form
– OGSI people did not want to use a draft standard
4GWSDL is a stepping stone to WSDL 1.2
4When WSDL 1.2 is released it will replace
GWSDL
9
OGSA-DAI Training Workshop, Release: P2R2
Tomcat
4Tomcat is the servlet container used in the
– official reference implementation for the Java Servlet and Java
Server Pages technologies
4More information from
– http://jakarta.apache.org/tomcat/
4Other possible hosting environments:
–
–
–
–
10
IBM Websphere
Oracle Application Server
Microsoft .Net framework
JBOSS
OGSA-DAI Training Workshop, Release: P2R2
Axis
4Axis is an implementation of a SOAP engine
4It can run as a servlet on Tomcat
4It is extensible through a handler chain
framework
4More information from
– http://ws.apache.org/axis/
11
OGSA-DAI Training Workshop, Release: P2R2
Tools
Ant
4Ant is a flexible build tool for multiple platforms
– Replacement for Makefiles
4Mainly Java orientated
4XML based as well
4More information from
– http://ant.apache.org
13
OGSA-DAI Training Workshop, Release: P2R2
Log4J
4Log4J is a framework for efficiently inserting
logging statements in Java code
4Supports detailed context for application
warnings and failures
4Supports inheritance of loggers
4More information from
– http://jakarta.apache.org/log4j/docs/
14
OGSA-DAI Training Workshop, Release: P2R2
Databases
SQL
4SQL is a database sub-language that is used
for accessing relational databases.
4A database sub-language is one that is used in
association with some other language e.g.
Java, for the purpose of accessing a database.
4SQL-92 is a particular specification supported
by many relational databases.
4More information from
– http://www.sqlstandards.org/
16
OGSA-DAI Training Workshop, Release: P2R2
Java DataBase Connectivity
4JDBC technology is an API that lets you
– access virtually any tabular data source from Java
– Provides cross-DBMS connectivity to a wide range of SQL
databases
4In theory, it also provides access to other
tabular data sources, such as
– spreadsheets or
– flat files.
4More information from
– http://java.sun.com/products/jdbc/
17
OGSA-DAI Training Workshop, Release: P2R2
Relational Databases
4MySQL
–
–
–
–
Open source relational database
Supports SQL’92
No support for atomic operations, triggers, rollback
More information:
• http://www.mysql.com
4DB2
–
–
–
–
IBM’s flagship database product
Supports SQL’92
Support for atomic operations, triggers, rollback
More information:
• http://www.ibm.com/software/data/db2/
18
OGSA-DAI Training Workshop, Release: P2R2
Prepared Statements
4Prepared statements and parameterised
queries allow databases to return results more
efficiently.
– Queries are precompiled and stored in the DBMS
– Parameter replacement can be used to modify data
inputs/outputs
4Database access plans can be cached and
reused
– E.g. select a,b from t where c=?
19
OGSA-DAI Training Workshop, Release: P2R2
XML:DB
4The XML:DB Initiative aims to
– develop a set of standards to allow interoperability between the
different XML databases available
4They produce defacto standards
4Three types of XML databases:
– Native XML database (NXD)
– XML enabled database (XEDB)
– Hybrid XML database (HXD)
4More information from
– http://www.xmldb.org
20
OGSA-DAI Training Workshop, Release: P2R2
XPath
4 XPath is a language
–
–
–
–
for addressing parts of an XML document,
designed to be used by both XSLT and Xpointer
W3C recommendation at version 1.0
There is a Version 2.0 working draft
4 XPath is the current de facto NXD query language
– is has been extended slightly to allow queries across collections of
documents
4 But XPath still has a number of limitations
–
–
–
–
No grouping,
No sorting,
No cross document joins
Poor support for data types.
4 More information from:
– http://www.w3.org/TR/xpath
21
OGSA-DAI Training Workshop, Release: P2R2
XUpdate
4 The XUpdate specification:
– provides open and flexible update facilities to modify data in XML
documents
– gives the ability to modify real documents or virtual documents
retrieved from XML databases
– makes extensive use of the expression language defined by XPath for
selecting elements for updating and for conditional processing.
– is a pure descriptive language which is designed with references to
the definition of XSL Transformations.
4 Comes from the XMLDB stable
4 An update in the XUpdate language is expressed as a
well-formed XML document.
4 More information from
– http://www.xmldb.org/xupdate/index.html
22
OGSA-DAI Training Workshop, Release: P2R2
Other XML APIs
4 XQuery
– W3C working draft recommendation
• designed for processing XML data.
• not only files in XML format, but also other data including databases
whose structure -- nested, named trees with attributes -- is similar to XML.
• everything is an expression which evaluates to a value
– More information:
• http://www.w3.org/XML/Query
4 SiXDML (Simple XML Manipulation Language)
– designed to create a common syntax and semantics for performing
tasks most often required of XML repositories
– SiXDML consists of two parts:
• a data definition and manipulation language inspired by SQL
• an API based on the XML:DB Database API.
– More information:
• http://www.xmldb.org/sixdml/index.html
23
OGSA-DAI Training Workshop, Release: P2R2
Xindice
4Xindice is a DBMS designed to store XML data
– It is an example of a native XML database (NXD)
– Uses
• XPath and
• XUpdate
– Designed specifically for storing
• many small/medium sized documents,
• not one large document
4Open source from Apache project
4More information from
– http://xml.apache.org/xindice
24
OGSA-DAI Training Workshop, Release: P2R2
Grids
What is OGSA?
4 OGSA pulls together Open Grid Architecture and Web
Services to form Grid Services.
– Open Grid Architecture + Web Services = Grid Services
4 Grid Services are
–
–
–
–
dynamic,
transient,
have state (i.e. have a finite lifetime) and
are defined by a well defined set of interfaces and behaviours.
4 The interfaces and behaviours describing Grid
Services can be written in an XML schema based
WSDL document.
– Other implementations are possible.
26
OGSA-DAI Training Workshop, Release: P2R2
What is OGSA?
The Best of Both Worlds
Open Grid Services Architecture
Share
Access Manage
resource resource resource
Continuous
Availability
Applications on
demand
Secure and
universal access
Business
integration
Web Services
27
Resources
on demand
Global
Accessibility
Vast resource
scalability
Grid Protocols
OGSA-DAI Training Workshop, Release: P2R2
What is OGSA?
OGSA Structure
System Management Services
Grid Services
OGSI – Open Grid Services Infrastructure
Web Services
28
OGSA-DAI Training Workshop, Release: P2R2
OGSI
ƒ Specifies minimum set of standards/behaviours with which
Grid Services must comply.
ƒ OGSA implementations MUST adhere to the OGSI
specifications of Grid Services.
ƒ Exploits existing Web Services properties
• Interface abstraction (WSDL), described through PortTypes.
• Uses WS protocols, language, and is hosting platform independent.
ƒ Enhancement to web services
• Allow state management, event notification.
• Have reference handles for service access.
• Implement lifecycle management.
• service data extension through Service Data Elements (SDEs).
29
OGSA-DAI Training Workshop, Release: P2R2
Grid Services
4 Grid Services can be described using WSDL documents
(although this is implementation independent).
4 They consist of interfaces, which are then essentially WSDL
PortTypes.
4 PortTypes include a set of Service Data Elements, which are
used to describe the properties and capabilities of Grid
Services.
4 Grid Service Factory (GSF) services are used to instantiate
Grid Services.
4 Grid Service Registry (GSR) services are used to register
factory services for look up by clients and users.
4 All Grid Services must include a GridService PortType.
30
OGSA-DAI Training Workshop, Release: P2R2
Anatomy of a Grid Service
• Service Data Access
• Lifetime Management
GridService
(required)
Other Interfaces
(Optional)
•Service creation (Factory)
•Service discovery (Registry)
•Notification
•Handle Management
•Other functions e.g.
Handle
Handle
Element
Element
Service
Data
Element
Grid Service
•Workflow
•Auditing
•Resource Management
Implementation
Hosting Environment
31
OGSA-DAI Training Workshop, Release: P2R2
Anatomy of a Grid Service
• Service Data Access
• Lifetime Management
GridService
(required)
Other Interfaces
(Optional)
•Service creation (Factory)
•Service discovery (Registry)
•Notification
•Handle Management
•Other functions e.g.
Handle
Handle
Element
Element
Service
Data
Element
•Workflow
•Auditing
•Resource Management
Implementation
Hosting Environment
32
OGSA-DAI Training Workshop, Release: P2R2
Anatomy of a Grid Service
• Service Data Access
• Lifetime Management
GridService
(required)
Other Interfaces
(Optional)
•Service creation (Factory)
•Service discovery (Registry)
•Notification
•Handle Management
•Other functions e.g.
Handle
Handle
Element
Element
Element
•Workflow
•Auditing
•Resource Management
Implementation
Hosting Environment
33
OGSA-DAI Training Workshop, Release: P2R2
Service Types
4 Service (component) implemented as a Java class
4 Implements the PortType interfaces and extends
some base class
public class MyGridService
extends
implements
BaseGridService
PortTypeOne,
PortTypeTwo,
PortTypeThree {
4 Here BaseGridService implements common
GridService interface functions
4 Other common functions are reused through
delegation
4 This class is instantiated in order to create a service
instance
36
OGSA-DAI Training Workshop, Release: P2R2
OGSA PortTypes
<<Interface>>
PortType
(from org.w3c.wsdl)
<<Interface>>
GridService
findServiceData()
requestTerminationTimeAfter()
requestTerminationTimeBefore()
destroy()
SDEs
<<Interface>>
NotificationSource
subscribe()
37
<<Interface>>
Factory
createService()
<<Interface>>
Registration
registerService()
unregisterService()
<<Interface>>
NotificationSink
deliverNotification()
<<Interface>>
Handl eResolver
f indByHandle()
<<Interface>>
NotificationSub
scription
OGSA-DAI Training Workshop, Release: P2R2
Grid Services
4Grid Services are identified by means of a
– Grid Service Handle (GSH), which is used to find the
– Grid Service Reference (GSR) that is unique to an instance of
a Grid Service.
– The HandleResolver service is used to go from GSH to GSR.
4 The GSH is a type of URI (or URL) and is constant for
the lifetime of the Grid Service.
4 The GSR is bound to the Grid Service instance. It is
the representation of the interfaces, and may be a
WSDL document for example, of that service instance
and can change if the service instance evolves.
38
OGSA-DAI Training Workshop, Release: P2R2
Globus’ OGSA Implementation
4 Technology Preview 1
4 Technology Preview 2
4 Technology Preview 3
4 Technology Preview 4
4 Technology Preview 5 – December 02
4 Globus Toolkit 3 Alpha – January 03
4 Globus Toolkit 3 Beta – end May 03
4 Globus Toolkit 3 Release – end June 03
39
OGSA-DAI Training Workshop, Release: P2R2
Globus Toolkit 3
4Globus Toolkit 2 was a one of the leading
middleware for grid applications
4Globus Toolkit 3 takes the features of GT2 and
incorporates the OGSA paradigm
4GT3 aims to be a reference implementation of
the OGSI spec (core services) as well as
providing higher level services for e.g. job
submission, resource discovery.
4More information from:
– http://www.globus.org/toolkit/gt3-factsheet.html
40
OGSA-DAI Training Workshop, Release: P2R2
GridFTP
4GridFTP is a high-performance, secure,
reliable data transfer protocol optimised for
high-bandwidth wide-area networks.
4The GridFTP protocol is based on FTP, the
highly-popular Internet file transfer protocol.
4More information from
– http://www.globus.org/datagrid/gridftp.html
41
OGSA-DAI Training Workshop, Release: P2R2
GGF
4The Global Grid Forum:
– Is the Grid equivalent of the W3C and IETF bodies.
– Meets three times a year.
– Facilitates the development of implementation and platform
independent Grid standards and protocols.
– Operates as a number of;
• working groups (WGs) which produce recommendations on
specific areas, and
• research groups (RGs) which are longer term groups looking into
issues that feed into short term WGs.
4More information from
– http://www.ggf.org
42
OGSA-DAI Training Workshop, Release: P2R2
Disclaimer
4Grid Development:
•
•
•
•
new and developing protocols and standards,
lots of issues are not yet “set in stone”,
ongoing, iterative development process,
facilitated through the Global Grid Forum (alongside W3C, OASIS
and IETF).
4Grids are complicated systems:
•
•
•
•
43
complex set of interactions,
between many components (services in OGSA),
You can know the technology…
… but it’s non-trivial social and political issues that can hinder
development.
OGSA-DAI Training Workshop, Release: P2R2
***