The document discusses and compares different architectural styles for distributed systems, focusing on Web Services, REST, and Instant Messaging. It summarizes the requirements for grid computing including scalability, interoperability, pervasiveness, and network efficiency. It then provides details on the Web Services Architecture (WSA) and related WS-* standards, and how they have been used to implement grid computing. It also describes the constraints-based Representational State Transfer (REST) architectural style and compares it to the less constrained WSA.
The E-Ball concept pc is a sphere shaped pc which is the smallest design among all the laptops and desktops.
This concept PC will measure 160mm in diameter and it was designed for Microsoft Windows OS.
This computer has all the features like a traditional computer, like, mouse, dvd, large screen display, mother-board, hard
drive, web came ,modem, LAN& WAN slots etc.
Free Space Optics (FSO) communications, also called Free Space Photonics (FSP) or Optical Wireless, refers to the transmission of modulated visible or infrared (IR) beams through the atmosphere to obtain optical communications. Like fiber, Free Space Optics (FSO) uses lasers to transmit data, but instead of enclosing the data stream in a glass fiber, it is transmitted through the air. Free Space Optics (FSO) works on the same basic principle as Infrared television remote controls, wireless keyboards
A basic idiots guide to Barcodes provided by a company who have been supplying barcode labels for 25+ years and as a way to help others when they have to order bar code labels and do not know the jargon being used.
E-paper is a revolutionary material that can be used to make next generation electronic displays. It is portable reusable storage and display medium that look like paper but can be repeatedly written one thousands of times. These displays make the beginning of a new area for battery power information applications such as cell phones, pagers, watches and hand-held computers etc.
Like traditional paper, E-paper must be lightweight, flexible, glare free and low cost. Research found that in just few years this technology could replace paper in many situations and leading us ink a truly paperless world.
Introduction to digital image processing, image processing, digital image, analog image, formation of digital image, level of digital image processing, components of a digital image processing system, advantages of digital image processing, limitations of digital image processing, fields of digital image processing, ultrasound imaging, x-ray imaging, SEM, PET, TEM
The E-Ball concept pc is a sphere shaped pc which is the smallest design among all the laptops and desktops.
This concept PC will measure 160mm in diameter and it was designed for Microsoft Windows OS.
This computer has all the features like a traditional computer, like, mouse, dvd, large screen display, mother-board, hard
drive, web came ,modem, LAN& WAN slots etc.
Free Space Optics (FSO) communications, also called Free Space Photonics (FSP) or Optical Wireless, refers to the transmission of modulated visible or infrared (IR) beams through the atmosphere to obtain optical communications. Like fiber, Free Space Optics (FSO) uses lasers to transmit data, but instead of enclosing the data stream in a glass fiber, it is transmitted through the air. Free Space Optics (FSO) works on the same basic principle as Infrared television remote controls, wireless keyboards
A basic idiots guide to Barcodes provided by a company who have been supplying barcode labels for 25+ years and as a way to help others when they have to order bar code labels and do not know the jargon being used.
E-paper is a revolutionary material that can be used to make next generation electronic displays. It is portable reusable storage and display medium that look like paper but can be repeatedly written one thousands of times. These displays make the beginning of a new area for battery power information applications such as cell phones, pagers, watches and hand-held computers etc.
Like traditional paper, E-paper must be lightweight, flexible, glare free and low cost. Research found that in just few years this technology could replace paper in many situations and leading us ink a truly paperless world.
Introduction to digital image processing, image processing, digital image, analog image, formation of digital image, level of digital image processing, components of a digital image processing system, advantages of digital image processing, limitations of digital image processing, fields of digital image processing, ultrasound imaging, x-ray imaging, SEM, PET, TEM
Presentation on OSGi Cloud Ecosystems (RFC 183) as given at EclipseCon Boston 2013. The RFC itself is available at http://www.osgi.org/Download/File?url=/download/osgi-early-draft-2013-03.pdf
Presentation on OSGi Cloud Ecosystems as presented during EclipseCon Europe 2012 (http://www.eclipsecon.org/europe2012/sessions/osgi-and-cloud-computing)
Services Oriented Infrastructure in a Web2.0 WorldLexumo
Tom Maguire discusses applying SOA Web 2.0 technologies, and open standards to the problems faced by IT in an ever changing world.
This session was recorded at EMC World 2007 in Orlando Florida
This webinar (done in December,2007) shows how the new Data Services capability in WSO2's Web Services Application Server can become a key component in your SOA/Data strategy. Using simple screens and a basic knowledge of SQL, any database programmer or administrator can configure and expose Data Services. As well as major databases such as Oracle, DB2 and MySQL, you can also extract data from Excel and CSV files.
Nuxeo JavaOne 2007 presentation (in original format)Stefane Fermigier
This session describes the architecture and implementation of an embeddable, extensible enterprise content management core for Java EE and simpler platforms. The presentation starts by describing the general architectural concepts used as building blocks:
• A schema and document model, reusing XML schemas and making good use of XML namespaces, where document types are built with several facets
• A repository model, using hierarchy and versioning, with the Content Repository API for Java (JSR 170) being one of the possible back ends
• A query model, based on the Java Persistence query language (JSR 220) and reusing the path-based concepts from Java Content Repositories (JCR)
• A fine-grained security model, compatible with WebDAV concepts and designed to provide flexible security policies
• An event model using synchronous and asynchronous events, allowing bridging through Java Message Service (JMS) or other systems to other event-enabled frameworks
• A directory model, representing access to external data sources using the same concepts as for documents but taking advantage of the specificities of the data back ends
Suitable abstraction layers are put in place to provide the required level of flexibility. One of the main architectural tasks is to find commonalities in all the systems used (or whose use is planned in the future) so framework users need to learn and use a minimal number of concepts. The result is a set of concepts that are fundamental to enterprise document management and are usable through direct Java technology-based APIs, Java EE APIs, or SOA. The presentation shows, for each of the main components, which challenges have been met and overcome when building a framework in which all components are designed to be improved and replaced by different implementations without sacrificing backward compatibility with existing ones.
The described implementation, Nuxeo Core, can be embedded in a basic Java technology-based framework based on OSGi (such as Eclipse) or in one based on Java EE, according to the needs of the application using it. This means that the core has to function without relying on Java EE services but also has to take advantage of them when they are available (providing clustering, messaging, caching, remoting, and advanced deployment).
Exploring Data Integration Capabilities of the WSO2 PlatformWSO2
To view recording of this webinar please use the below URL:
http://wso2.com/library/webinars/2015/06/exploring-data-integration-capabilities-of-the-wso2-platform/
You will learn the following:
How siloed data in an enterprise can be quickly exposed as a service
How this data can be integrated with various systems
How WSO2 DSS can be used with WSO2 Enterprise Service Bus for data intensive applications that support security, transformation, and distributed transactions
This talk was given at SOA Symposium in Amsterdam in 2008. It is a perspective on Enterprise Mashup architectures can be constructed by using data services, RIA, REST, empowering the client platforms.
Similar to If Web Services are the Answer, What's The Question (20)
Wikipedia at the Royal Society: The Good, the Bad and the UglyDuncan Hull
Wikipedia has a troubled relationship with scientists and their science. Many scientists are wary of editing Wikipedia and reluctant to contribute their knowledge to it, despite its global reach. Consequently, Wikipedia's coverage of Science is very variable with many notable scientists work either completely absent or poorly described.
There are several WikiProjects that are tackling these problems across Science, including in Computational Biology, Medicine, Cell Biology, Physiology and Women Scientists.
This talk will describe how the WikiProject Royal Society has addressed these issues, through its Wikipedian in Residence scheme. We will examine the outcomes of the project as well as the challenges that remain for this ongoing collaboration between the Royal Society and Wikimedia UK.
We will discuss the good, bad and "ugly" aspects of scientists Wiki-biographies (quick biographies in Wikipedia) and draw conclusions about improving coverage of Scientists, and their Science in Wikipedia using the resources of a learned academic society.
Speaker biography: Dr. Duncan Hull is a lecturer in the School of Computer Science at the University of Manchester who started editing Wikipedia in 2004. He helped setup the Wikipedian in Residence scheme at the Royal Society in 2012.
Bibliography 2.0: A citeulike case study from the Wellcome Trust Genome CampusDuncan Hull
Abstract: This talk will describe the use of http://www.citeulike.org to manage and share bibliographic references among 1300 scientists and engineers working at the Sanger Institute (http://www.sanger.ac.uk) and European Bioinformatics Insitute (http://www.ebi.ac.uk) based on the Wellcome Trust Genome Campus in Cambridge, UK. Using data from references shared so far, we will illustrate the costs, benefits and adoption of citeulike to create and share bibliographic data on the web.
Presentation from The Influence and Impact of Web 2.0 on Various Applications at the National e-Science Centre, Edinburgh, UK.
Part of a joint presentation with Midori Harris comparing OWL (Web Ontology Language) and OBO (Open Biomedical Ontologies) as ontology languages, This presentation concentrates on OWL, Midori Harris presented OBO.
Accessing small molecule data using ChEBIDuncan Hull
Presentation on Chemical Entities of Biological Interest (ChEBI) for the Programmatic Access to Biological Databases (Perl) course
22-26 February 2010 @ EBI
Slides from the "Author Identity – Creating a new kind of reputation online" session at Science Online London (solo09) with Duncan Hull, Geoffrey Bilder, Michael Habib, Reynold Guida
ResearcherID, Contributor ID, Scopus Author ID, etc. help to connect your scientific record. How do these tools connect to your online identity, and how can OpenID and other tools be integrated? How can we build an online reputation and when should we worry about our privacy?
Digital Identity is fundamental to collaboration in bioinformatics research and development because it enables attribution, contribution, publication to be recorded and quantified.
However, current models of identity are often obsolete and have problems capturing both small contributions "microattribution" and large contributions "mega-attribution" in Science. Without adequate identity mechanisms, the incentive for collaboration can be reduced, and the utility of collaborative social tools hindered.
Using examples of metabolic pathway analysis with the taverna workbench and myexperiment.org, this talk will illustrate problems and solutions to identifying scientists accurately and effectively in collaborative bioinformatics networks on the Web.
The Year of Blogging Dangerously: Lessons from the "Blogosphere". This talk will describe how to build an institutional repository using free (or cheap) web-based and blogging tools including flickr.com, slideshare.net, citeulike.org, wordpress.com, myexperiment.org and friendfeed.com. We will discuss some strengths and limitations of these tools and what Institutional Repositories can learn from them.
Defrosting the Digital Library: A survey of bibliographic tools for the next ...Duncan Hull
After centuries with little change, scientific libraries have recently experienced massive upheaval. From being almost entirely paper-based, most libraries are now almost completely digital. This information revolution has all happened in less than 20 years and has created many novel opportunities and threats for scientists, publishers and libraries.
Today, we are struggling with an embarassing wealth of digital knowledge on the Web. Most scientists access this knowledge through some kind of digital library, however these places can be cold, impersonal, isolated, and inaccessible places. Many libraries are still clinging to obsolete models of identity, attribution, contribution, citation and publication.
Based on a review published in PLoS Computational Biology, http://pubmed.gov/18974831 this talk will discuss the current chilly state of digital libraries for biologists, chemists and informaticians, including PubMed and Google Scholar. We highlight problems and solutions to the coupling and decoupling of publication data and metadata, with a tool called http://www.citeulike.org. This software tool exploits the Web to make digital libraries “warmer”: more personal, sociable, integrated, and accessible places.
Finally issues that will help or hinder the continued warming of libraries in the future, particularly the accurate identity of authors and their publications, are briefly introduced. These are discussed in the context of the BBSRC funded REFINE project, at the National Centre for Text Mining (NaCTeM.ac.uk), which is linking biochemical pathway data with evidence for pathways from the PubMed database.
what is the best method to sell pi coins in 2024DOT TECH
The best way to sell your pi coins safely is trading with an exchange..but since pi is not launched in any exchange, and second option is through a VERIFIED pi merchant.
Who is a pi merchant?
A pi merchant is someone who buys pi coins from miners and pioneers and resell them to Investors looking forward to hold massive amounts before mainnet launch in 2026.
I will leave the telegram contact of my personal pi merchant to trade pi coins with.
@Pi_vendor_247
If you are looking for a pi coin investor. Then look no further because I have the right one he is a pi vendor (he buy and resell to whales in China). I met him on a crypto conference and ever since I and my friends have sold more than 10k pi coins to him And he bought all and still want more. I will drop his telegram handle below just send him a message.
@Pi_vendor_247
how to sell pi coins in all Africa Countries.DOT TECH
Yes. You can sell your pi network for other cryptocurrencies like Bitcoin, usdt , Ethereum and other currencies And this is done easily with the help from a pi merchant.
What is a pi merchant ?
Since pi is not launched yet in any exchange. The only way you can sell right now is through merchants.
A verified Pi merchant is someone who buys pi network coins from miners and resell them to investors looking forward to hold massive quantities of pi coins before mainnet launch in 2026.
I will leave the telegram contact of my personal pi merchant to trade with.
@Pi_vendor_247
Turin Startup Ecosystem 2024 - Ricerca sulle Startup e il Sistema dell'Innov...Quotidiano Piemontese
Turin Startup Ecosystem 2024
Una ricerca de il Club degli Investitori, in collaborazione con ToTeM Torino Tech Map e con il supporto della ESCP Business School e di Growth Capital
Falcon stands out as a top-tier P2P Invoice Discounting platform in India, bridging esteemed blue-chip companies and eager investors. Our goal is to transform the investment landscape in India by establishing a comprehensive destination for borrowers and investors with diverse profiles and needs, all while minimizing risk. What sets Falcon apart is the elimination of intermediaries such as commercial banks and depository institutions, allowing investors to enjoy higher yields.
when will pi network coin be available on crypto exchange.DOT TECH
There is no set date for when Pi coins will enter the market.
However, the developers are working hard to get them released as soon as possible.
Once they are available, users will be able to exchange other cryptocurrencies for Pi coins on designated exchanges.
But for now the only way to sell your pi coins is through verified pi vendor.
Here is the telegram contact of my personal pi vendor
@Pi_vendor_247
what is the future of Pi Network currency.DOT TECH
The future of the Pi cryptocurrency is uncertain, and its success will depend on several factors. Pi is a relatively new cryptocurrency that aims to be user-friendly and accessible to a wide audience. Here are a few key considerations for its future:
Message: @Pi_vendor_247 on telegram if u want to sell PI COINS.
1. Mainnet Launch: As of my last knowledge update in January 2022, Pi was still in the testnet phase. Its success will depend on a successful transition to a mainnet, where actual transactions can take place.
2. User Adoption: Pi's success will be closely tied to user adoption. The more users who join the network and actively participate, the stronger the ecosystem can become.
3. Utility and Use Cases: For a cryptocurrency to thrive, it must offer utility and practical use cases. The Pi team has talked about various applications, including peer-to-peer transactions, smart contracts, and more. The development and implementation of these features will be essential.
4. Regulatory Environment: The regulatory environment for cryptocurrencies is evolving globally. How Pi navigates and complies with regulations in various jurisdictions will significantly impact its future.
5. Technology Development: The Pi network must continue to develop and improve its technology, security, and scalability to compete with established cryptocurrencies.
6. Community Engagement: The Pi community plays a critical role in its future. Engaged users can help build trust and grow the network.
7. Monetization and Sustainability: The Pi team's monetization strategy, such as fees, partnerships, or other revenue sources, will affect its long-term sustainability.
It's essential to approach Pi or any new cryptocurrency with caution and conduct due diligence. Cryptocurrency investments involve risks, and potential rewards can be uncertain. The success and future of Pi will depend on the collective efforts of its team, community, and the broader cryptocurrency market dynamics. It's advisable to stay updated on Pi's development and follow any updates from the official Pi Network website or announcements from the team.
how to sell pi coins at high rate quickly.DOT TECH
Where can I sell my pi coins at a high rate.
Pi is not launched yet on any exchange. But one can easily sell his or her pi coins to investors who want to hold pi till mainnet launch.
This means crypto whales want to hold pi. And you can get a good rate for selling pi to them. I will leave the telegram contact of my personal pi vendor below.
A vendor is someone who buys from a miner and resell it to a holder or crypto whale.
Here is the telegram contact of my vendor:
@Pi_vendor_247
Even tho Pi network is not listed on any exchange yet.
Buying/Selling or investing in pi network coins is highly possible through the help of vendors. You can buy from vendors[ buy directly from the pi network miners and resell it]. I will leave the telegram contact of my personal vendor.
@Pi_vendor_247
What website can I sell pi coins securely.DOT TECH
Currently there are no website or exchange that allow buying or selling of pi coins..
But you can still easily sell pi coins, by reselling it to exchanges/crypto whales interested in holding thousands of pi coins before the mainnet launch.
Who is a pi merchant?
A pi merchant is someone who buys pi coins from miners and resell to these crypto whales and holders of pi..
This is because pi network is not doing any pre-sale. The only way exchanges can get pi is by buying from miners and pi merchants stands in between the miners and the exchanges.
How can I sell my pi coins?
Selling pi coins is really easy, but first you need to migrate to mainnet wallet before you can do that. I will leave the telegram contact of my personal pi merchant to trade with.
Tele-gram.
@Pi_vendor_247
What price will pi network be listed on exchangesDOT TECH
The rate at which pi will be listed is practically unknown. But due to speculations surrounding it the predicted rate is tends to be from 30$ — 50$.
So if you are interested in selling your pi network coins at a high rate tho. Or you can't wait till the mainnet launch in 2026. You can easily trade your pi coins with a merchant.
A merchant is someone who buys pi coins from miners and resell them to Investors looking forward to hold massive quantities till mainnet launch.
I will leave the telegram contact of my personal pi vendor to trade with.
@Pi_vendor_247
how to sell pi coins in South Korea profitably.DOT TECH
Yes. You can sell your pi network coins in South Korea or any other country, by finding a verified pi merchant
What is a verified pi merchant?
Since pi network is not launched yet on any exchange, the only way you can sell pi coins is by selling to a verified pi merchant, and this is because pi network is not launched yet on any exchange and no pre-sale or ico offerings Is done on pi.
Since there is no pre-sale, the only way exchanges can get pi is by buying from miners. So a pi merchant facilitates these transactions by acting as a bridge for both transactions.
How can i find a pi vendor/merchant?
Well for those who haven't traded with a pi merchant or who don't already have one. I will leave the telegram id of my personal pi merchant who i trade pi with.
Tele gram: @Pi_vendor_247
#pi #sell #nigeria #pinetwork #picoins #sellpi #Nigerian #tradepi #pinetworkcoins #sellmypi
how to sell pi coins effectively (from 50 - 100k pi)DOT TECH
Anywhere in the world, including Africa, America, and Europe, you can sell Pi Network Coins online and receive cash through online payment options.
Pi has not yet been launched on any exchange because we are currently using the confined Mainnet. The planned launch date for Pi is June 28, 2026.
Reselling to investors who want to hold until the mainnet launch in 2026 is currently the sole way to sell.
Consequently, right now. All you need to do is select the right pi network provider.
Who is a pi merchant?
An individual who buys coins from miners on the pi network and resells them to investors hoping to hang onto them until the mainnet is launched is known as a pi merchant.
debuts.
I'll provide you the Telegram username
@Pi_vendor_247
Resume
• Real GDP growth slowed down due to problems with access to electricity caused by the destruction of manoeuvrable electricity generation by Russian drones and missiles.
• Exports and imports continued growing due to better logistics through the Ukrainian sea corridor and road. Polish farmers and drivers stopped blocking borders at the end of April.
• In April, both the Tax and Customs Services over-executed the revenue plan. Moreover, the NBU transferred twice the planned profit to the budget.
• The European side approved the Ukraine Plan, which the government adopted to determine indicators for the Ukraine Facility. That approval will allow Ukraine to receive a EUR 1.9 bn loan from the EU in May. At the same time, the EU provided Ukraine with a EUR 1.5 bn loan in April, as the government fulfilled five indicators under the Ukraine Plan.
• The USA has finally approved an aid package for Ukraine, which includes USD 7.8 bn of budget support; however, the conditions and timing of the assistance are still unknown.
• As in March, annual consumer inflation amounted to 3.2% yoy in April.
• At the April monetary policy meeting, the NBU again reduced the key policy rate from 14.5% to 13.5% per annum.
• Over the past four weeks, the hryvnia exchange rate has stabilized in the UAH 39-40 per USD range.
If Web Services are the Answer, What's The Question
1. If Web Services are the Answer,
What’s the Question?
Michael Parkin
Supervisor: John Brooke
IMG Seminar
17 January 2007
2. Acknowledgments & Sources
• Thanks to Dean Kuo, Mark McKeown, Bruno Harbulot, Donal Fellows
• Lots of stuff taken from blogs and web articles
• All quotes are acknowledged and linked to where possible
IMG Seminar
17 January 2007
3. Overview
• Grid computing & it’s requirements
• Introduction of architectural styles:
• Web Services Architecture (WSA) and WS-*
• Representational State Transfer (REST)
• Instant Messaging (IM)
• Evaluation of Web Services, REST and IM
• Using the requirements of Grid computing
• The question is?
IMG Seminar
17 January 2007
5. Grid Computing is...
... a new infrastructure that builds on today’s Internet and
Web to enable and exploit large-scale sharing of resources within
distributed groups.
“The Grid”
Ian Foster, ClusterWorld Magazine (January 2004)
... coordinated resource sharing among dynamic collections of
individuals, institutions, and resources.
“The Anatomy of the Grid”
Ian Foster, et al (2001)
... internet-scale distributed computing.
“Distributed Computing Economics”
Jim Gray [Microsoft Research]
IMG Seminar
17 January 2007
6. Non-functional Requirements
• Scalability and interoperation
• Large/internet-scale dynamic sharing of resources
• We need to connect lots of diverse/heterogeneous entities together
• Pervasiveness
• ... through simple clients and consistent implementations
• Network efficiency
• ... this is a distributed system, after all
• Return to these later ...
IMG Seminar
17 January 2007
8. Web Services Architecture
The only game in town
Anon (though attributed to many)
A Web service is a software system designed to support interoperable
machine-to-machine interaction over a network. It has an interface
described in a machine-processable format (WSDL). Other systems
interact with the Web service ... using SOAP messages.
Web Services Architecture, W3C
• WSA is just SOAP (structured XML) + WSDL
IMG Seminar
17 January 2007
9. WSA Constraints
[An Architecture’s] properties are created by the application of constraints
Roy Fielding’s PhD. Thesis
• A constraint is a condition that a solution must meet in order to be
acceptable - a confinement of all possible solutions
• Lack of constraints on the WSA other than
• Use of SOAP + WSDL
• Service specific interfaces
• i.e. no restriction on interfaces or message representations
• Sender / receiver pattern
• “Effectively unconstrained” - all possible solutions are acceptable
IMG Seminar
17 January 2007
10. No constraints...
IMG Seminar
“The Sugar House” Richard Greaves, 2001 17 January 2007
11. Web Services Standards
Web services standards compose together to provide interoperable
protocols ... in loosely coupled systems. The specifications build
on top of the core XML and SOAP standards.
“Web Service Specifications” Microsoft
• Collectively known as Web Service stack or WS-*
• 50+ specifing aspects of reliability, security, transactions, etc.
• WS-* are constraints on the WSA
• Defined though standards bodies (OGF, W3C, OASIS, EMCA?) before
being implemented
• No reference implementations
IMG Seminar
17 January 2007
12. Grid & WS-*
• Since 2002 Grid computing is officially implemented using WS-*
• First through Open Grid Services Infrastructure ...
• ... then through the WS-ResourceFramework (WS-RF) family (2004)
• WS-RF describes the relationship between WSA & WS-*
• As Web Services are stateless WS-Resource describes a stateful
resource
• “Each message carries some information that identifies the [stateful]
resource behind the service which should be the logical receiver of
the message” Savas Parastatidis [Microsoft]
IMG Seminar
17 January 2007
13. The WS-RF Family
• WS-Resource
• WS-ResourceProperty
• WS-ResourceLifetime
• WS-BaseFaults
• WS-RenewableReferences
• WS-ServiceGroup
• WS-Notification
IMG Seminar
17 January 2007
15. REST
• REpresentational State Transfer
• The architecture of the Web introduced in Roy Fielding’s PhD. thesis
Fetch representation
Client Resource
Representation
• Not a standard, but it uses common standards
• Best known implementation of REST is HTTP
• Resource - not service - orientation
IMG Seminar
17 January 2007
16. Service vs Resource Orientation
/jobs
GET - list all jobs
PUT - unused
• The resource is the central abstraction - POST - add new job
DELETE - unused
not the service
/job/[id]
GET - get job details
PUT - update job
JobManagementService POST - unused
+ ID submitJob (u_id: ID, j:Job) DELETE - cancel job
+ void cancelJob (j_id: ID)
+ Job getJobDetail (j_id: ID)
+ Job[] getJobs(u_id: ID) <<interface>>
/users
Resource
GET - list all users
GET
PUT - unused
PUT
POST - create user
POST
DELETE - unused
DELETE
UserManagementService
+ ID createUser (u: User)
/user/[id]
+ User getUser (u_id: ID)
GET - return user
+ User[] getUsers ()
PUT - update user
POST - unused
DELETE - unused
/user/[id]/jobs
GET - return user's jobs
PUT -
IMG Seminar
POST - create new job
Adapted from: “REST - The Better Web Services Model”, Stefan Tilkov DELETE17 January 2007
-
17. REST Constraints
• Highly constrained architecture (cf. WSA)
• Self-descriptive messages
• ... stateless interaction
• ... resource representation
• “Hypermedia as engine of client state”
• Resource identification
• Name things with unique URIs
• Uniform interface
IMG Seminar
17 January 2007
19. REST and the Grid
• REST style is not used by the Grid
• Why can’t a Grid Virtual Organisation (VO) be a REST resource?
• Find VO member:
• Fetch /myVO/people/fred
• Returns representation of Fred in format requested
• If no representation returned, Fred’s not a member
• Used for role-based access control as part of my work
• Very lightweight and interoperable ...
IMG Seminar
17 January 2007
21. Instant Messaging
• Hub and spoke/email-type infrastructure
• Not just text: Google’s Jingle library can stream VOIP and Video
IMG Seminar
17 January 2007
22. IM Constraints
• Asynchronous, routed messaging
• Open connection to server is used as bi-directional message pipe
• Document-style interaction
• Complexity is in the message - not the interface (cf. REST self-
describing message)
• Unique naming of servers and clients
• Number (ICQ) or email style (name@domain)
• Presence of clients can be determined
• Clients may have multiple sessions with one or more other clients and
multi-user chats
IMG Seminar
17 January 2007
24. Just for Multi-User Chat?
• Multi User Chat can be used
as a messaging ‘bus’
• ‘Plug-in’ services across
domains
• Each client listens for a
message it’s interested in
• Ignores other messages
• A lightweight collaborative
environment
• Implemented using XMPP
IMG Seminar
17 January 2007
25. Grid Computing Requirements
• Scalability
• Interoperation
• Pervasiveness / simple clients
• Network efficiency
• How does each architecture do?
IMG Seminar
17 January 2007
27. WSA Scalability
• Remember - no constraints
• ... therefore an infinite number
ways to do things...
• ... which promotes coupling
• “Web services are effectively
unconstrained, and therefore
much more tightly coupled.”
Mark Baker [W3C Working
Groups]
• Loose coupling is better than tight
coupling for scalability
IMG Seminar
17 January 2007
28. WS-* Scalability / Interoperability
• Requires each service to be predictable and implement the same set of
specifications in the same way
• Specifications MUST be unambiguous
• Interoperability through consistency of implementations
• Most WS-* specifications aren’t unambiguous ...
• ... and sometimes they’re deliberately ambiguous - e.g. WS-BA
• There’s no reference implementation to code to
• No consistency, therefore no reliability
IMG Seminar
17 January 2007
29. WS-* Scalability / Interoperability
This document does a disservice to the community; it is
ambiguous in many places, incomplete in others, and riddled with
errors throughout. Indeed any company that implemented it would
end up with an unreliable system.
Werner Vogels [CTO, Amazon] on WS-Reliability
IMG Seminar
17 January 2007
30. ?
IMG Seminar
“Untitled” Richard Greaves, 2001 17 January 2007
31. WS-Interoperability
Conformance to the Web services Addressing Test Suite does not
by itself enable a party to claim conformance with the Web
Services Addressing specification.
Disclaimer from the WS-Addressing test suite
IMG Seminar
17 January 2007
32. WS-Incoherence
• WS-Reliability or WS-ReliableMessaging ?
• WS-Management or WS-DistributedManagement ?
• WS-Eventing or WS-Notification ?
• WS-Context or WS-Session ?
• WS-RF or WS-Transfer ?
• Multiple ways of doing things
• e.g. SOAP vs Literal encoding, Document vs RPC style
• e.g. “4 ways to send SOAP attachments (DIME, MTOM, SOAP w.
Attachments, WS-I Attachments)” Dan Diephouse [XFire author]
IMG Seminar
17 January 2007
33. WS-* Stack Criticism
No matter how hard I try, I still think the WS-* stack is bloated, opaque,
and insanely complex. I think it’s going to be hard to understand, hard to
implement, hard to interoperate, and hard to secure.
Tim Bray [Director of Web Technologies, Sun Microsystems]
Much of [WS-* is] recently invented, untested and unproven
in the real world.
Sean McGrath [CTO, Propylon]
IMG Seminar
17 January 2007
34. “If you don’t like it, don’t use it”
Are there too many specs? If you think so, then there are.
So don't use them all.
You don't have to use any of them.
Matt Powell [Web Platform and Tools Marketing Team, Microsoft]
• OK, if within the same administrative domain - you are ‘God’
• Sixth fallacy of distributed computing is that “there is a single
administrator” Peter Deutsch [author of the definitive Smalltalk
implementation] via Mark Baker
IMG Seminar
17 January 2007
35. Across Administrative Domains
• Grid computing is about creating virtual organisations across
organizational boundaries
• “[Grid computing ] is distributed computing across multiple
administrative domains” Dave Snelling (via Mark McKeown)
• You can’t control who implements what WS-* specifications ...
• ... or how they interpret and implement it ...
• ... or which version they implement
• Tighter - not looser - coupling is required to solve these problems
IMG Seminar
17 January 2007
36. WS-Tooling Support
Tools are being created by people everywhere to make it so you can just
indicate the capabilities you need and the rest will be done for you.
Matt Powell
Each toolkit vendor is likely to interpret the specification somewhat
differently.
Werner Vogels [CTO, Amazon]
IMG Seminar
17 January 2007
37. REST Scalability & Interoperability
• The best known implementation of REST is HTTP
• The Web:
I look at Google and Amazon and EBay and Salesforce and see them doing
tens of millions of transactions a day involving pumping XML back and
forth over HTTP, and I can’t help noticing that they don’t seem to need
much WS-apparatus.
Tim Bray
• All clients can immediately interact with a resource once we know it’s
address because of uniform interface and operation semantics
IMG Seminar
17 January 2007
38. Even Looser Coupling
• Loose coupling in time is also possible
• HTTP has asynchronous communications built in ...
• GET empty job representation
• POST completed job representation to asynchronous job submission
resource (URL contained in empty job)
• Server returns a ‘202 Accepted’ message and either:
1. With “Reply-To” request header: a notification is sent to that
URL when the job is complete
2. Without “Reply-To” request header: a “Location” response
header is returned with a URL with the status/result
• ... in a standard way
IMG Seminar
17 January 2007
39. IM Scalability & Interoperability
• Considering XMPP, an open XML message based IM implementation...
• Scales very well
• Jabber has 40-50 million users (source: Wikipedia)
• Each XMPP server can support ~30-50,000 concurrent users
• Interoperability seems to be no problem
• Lots of heterogeneous clients connecting to lots of heterogeneous
servers
• Gateways to ‘closed’ IM implementations
• AIM, ICQ, etc.
• Well-defined and accepted message semantics
IMG Seminar
17 January 2007
41. Network Efficiency - A Note
• In a network-based application it is often the communications which are
the bottleneck
• Generally increased through the use of network intermediaries
• Caches, proxy servers, etc.
• Reduce the ‘distance’ a request has to go
• Relieves stress on the server/application
• An intermediary can only make a decisions when a client’s request
shows, in the clear, the targeted resource, and the method requested
is understood
IMG Seminar
Adapted from: “REST”, Roger L. Costello 17 January 2007
42. WSA Network Efficiency
• Most (all?) Web Services use SOAP/HTTP
• Can they re-use Web caches to increase efficiency?
• A SOAP message is always a HTTP POST operation
• A cache cannot know from the HTTP method whether the client is
doing a read, write, update or delete
• I don't know what operation is being
A SOAP URI is always to the SOAP server, not to the actual requested.
target
• I don't know which resource is being
Cache server cannot know from the URI what resource is being requested.
requested. I must forward the request
Message
Web
Client
Cache
EPR
operation = highFive() IMG Seminar
17 January 2007
43. Reuse or Abuse?
[Web Services are] on the web but they aren’t of the web. They
don’t use any of the web’s features, or interact with anything else
on the web. They just use HTTP as a transport protocol. They
could just as easily run over TCP and get better performance.
Leonard Richardson [co-author “REST Web Services”]
IMG Seminar
17 January 2007
44. REST Network Efficiency
• Uniform, clear semantics of the interface’s operations
• GET always means “retrieve the resource identified”
• PUT always means “replace resource identified with this new one”
• POST always means “submit this data for processing”
• DELETE always means “delete the resource identified”
• URI’s can be compared
• Allows optimization of the network (i.e. caching, comparison of
metainformation)
IMG Seminar
17 January 2007
45. IM Network Efficiency
• Connection overheads removed (client only connects once to server)
• Login to server once
• Open pipe is used as an asynchronous bi-directional messaging bus
• Only send messages once
• Stored on server if destination is unavailable
• Guaranteed in-oder delivery when client reconnects
• No need to poll - response comes asynchronously when ready
• But, all messages are routed via server - not the most efficient route
IMG Seminar
17 January 2007
46. Pervasiveness
pervade, v. “To spread, extend, diffuse; to
be present and apparent throughout.”
(Source OED)
IMG Seminar
17 January 2007
47. WS-* Pervasiveness
• Complexity of WS-* limits overall uptake of technology
• Clients are service specific
• Clients must be ‘active’
• ... no information about the possible state transitions for the client in
SOAP messages
• ... must process each message even if content has not changed
• ... therefore client more complex
• Stack overhead unsuitable for restricted/lightweight clients
IMG Seminar
17 January 2007
48. REST / IM Pervasiveness
• Simpler clients than WS clients as all possible state transitions are
contained in the returned message through hypermedia
• “REST is particularly useful for limited-profile devices such as PDAs
and mobile phones” Sun Microsystems
• More complex clients than REST, but simpler than WS-*
• New York Times: “... instant messaging is used in more than 80 percent
of corporations”
• No of IM accounts in 2006: 995 million (Source: Radichi Group)
IMG Seminar
17 January 2007
50. Finally ...What is the question?
• If Web Services are the answer:
What foundations do we choose for
limited-scale, tightly-coupled,
implementation dependent Grid?
• The question should be:
What foundations do we choose for
massively-scalable, loosely-coupled,
implementation independent, consistent Grid?
IMG Seminar
17 January 2007
51. Or...
vs
No architectural constraints? Architectural constraints?
52. Summary
• Grid computing is based on WS-*
• WS-* is widely acknowledged to be complex
• Across administrative domains you can’t control who implements
what and how they implement it
• Other architectures and technologies that meet the Grid’s requirements
should be considered
• These have been proven to be interoperable and scalable - the
ultimate goal of the Grid
IMG Seminar
17 January 2007