Petri nets. An interactive tutorial

I found a nice interactive tutorial that gives some examples of using Petri nets to model concurrent processes. Here is the famous problem with four philosophers modelled with Petri nets.

The history of social networking sites

I found following image while I was searching about the history of social networking sites.


Source is here

Web Services Ecosystems

The traditional definition of an ecosystem is something related to living things as the following found in the Merriam-Webster online dictionary,
"The complex of a community of organisms and its environment functioning as an ecological unit". Extending this to the world of web services with the concept of "a software as a service", as the backbone, today we are talking about Web Services Echo Systems.
The article by Alistair Barros and Marlon Dumas describes us, how different entities in the web services world plays different roles and how they are depending on each other forming an ecosystem. Also it shows how different entities are benefited by being part of this web services ecosystem. For example third party developers are developing services or service components and software companies acting as service brokers and integrators depending on them. Another example is how some companies address the space of interoperability and QoS issues on the basis of software as a service.
Also the paper shows unlike application servers, how business environment in an ecosystem evolve constraints. This is depending on the requirements of the demand side and the supply side
Demand side constrains on how services are
1. Discovered
2. Ranked
3. Authenticated
4. Mediated
5. Charged

While Supply side constrains on how services are
1. Published
2. Re-purposed through composition
3. Brokered
4. Re-provisioned through leasing and licensing

As we see that there are multiple entities are benefited under web services ecosystem, there are few obstacles on the way. The paper identifies three major fronts that the web services infrastructure will have to evolve

1.Flexible web services discovery:
Need to go beyond the conventional key word based searches. If the domain of the ecosystem is wider then key word based searches become unsuccessful. Instead it is advisable to use a combination of free-text and ontology-based searches.
2.Conversational multiparty interactions:
Service interactions are getting complex. Different transaction paths in a business process.
3.Service mediation and adaptation:
Services have different behaviours. Need to find cost-effective ways for service interface adaptation.

Intellectual property and researching in a university

While I engaged in an assignment for the subject "Research Commercialization" in this semester, I searched about how the intellectual property rights are applied to our research outcomes. In many universities, we, as research PhD students or research fellows, are bound by the rules of the university. I found this intellectual property rights case in the very country that I'm studying right now. Ultimately the court decided who is the real owner of the invention. It's the researcher, though he has used the university resources. May be the result of the case is dependent on that particular context but not in any case in the future. Here you find the story in short and here you'll see more details.

Open source, WS-Standards and Beyond

16/09/2008 @ Swinburne University of Technology

Open source, WS-Standards and Beyond - Upload a Document to Scribd

Read this document on Scribd: Open source, WS-Standards and Beyond

Folks, if u need the animated version of this or if u have any questions, drop an email (Right now I do not have any space to upload the original PPT). Alternatively meet me at Room 404 EN Building.

Murali from Moratuwa

The University of Moratuwa, SL, where I studied as an undergrad, is on news for it's proud product of "Murali", which is nothing but an eight legged robot for detecting land mines.
North-Eastern regions of Sri Lanka are one of the heavily mined areas in the world due to the war between SL government and Tigers. The war has come to a decisive stage as government is gaining control over many regions, but land mines can be a problem for years even after the war. Therefore, this kind of a product from Sri Lankan institute should be appreciated and supported.
The most important characteristic of Murali is its ability to access areas that cannot be accessed by other means. Also Murali is capable of collaborating with other Muralis operated in a particular area upon detection of a land mine.
Read more...

Murali, or the Moratuwa University Robot for Anti-Landmine Intelligence, is a result of project funded by National Science Foundation and efforts of students lead by Dr. Thrishantha Nanayakkara.

Watch video ...


PS: Sorry if I raised eyebrows of few cricket addicts with the title.

Federated registries and crawlers

Deepal has revealed some of the things we discussed over the chat during the last weekend regarding web services discovery mechanisms.
I started to look into WSO2 registry to help with another PhD student but didn’t have much time to dig into the architecture level as I was busy during last week with my studies.
Yeah… the problem with having multiple registries in a heterogeneous environment is that it makes really difficult to find web services information, which is essential part in SOA. As web services grows from hundreds to thousands, the consumers or the clients need to have an efficient way to locate them. And publishers also need to attract clients without going through other marketing channels and gimmicks.
One such approach is discussed in this paper, which uses a crawler engine to find web services. In this approach the Crawler Engine (WSCE) actively crawls excising UBRs and search engines to collect web services information. Thus a system can maintain most up-to-date information about available web services. Web services information can be found using existing web services registries and web services portals. And also via search engines, which is becoming popular.

[Source : Eyhab, A.-M. and H.M. Qusay, Investigating web services on the world wide web, in Proceeding of the 17th international conference on World Wide Web. 2008, ACM: Beijing, China]

But using search engines too have limitations as they do not recognize web services with basic service properties such as binding information, ports, operations etc. And search engines can cache/store WSDL documents but there is no business-centric model or adhering to web services standards.

Another approach discussed in this paper is to form a federation of registries. The current search facilities offered by the latest version of UDDI do not offer any special features for finding Web service registries depending on the business domains. And it is difficult to have a design and execution autonomy for affiliated registries. The approach discusses in the paper allows peer to peer network of private, semi-private and public UDDI registries, which allow transparent access to registries in a federated environment. Following are the essential features of the approach

-Participating registries are autonomous registries that can be private or public
-Participating registries can be part of multiple federations
-Participating registries can be heterogeneous. Can have different data models and APIs
-Participating registries can arbitrary join and leave the federation. This is something that we cannot achieve with the UDDI replication support in V3
-Participating registries will have the design and execution autonomy
-The federation of registries can be formed as a market place for common interests
-The XTRO or the extended registries ontology provides a way o do complex queries across federations

So, in overall there is a requirement of adhering to a common standards as well as developing mechanisms to retrieve web services information from the repositories built upon multiple standards. IMO the latter is much better as it does not limit to a particular standard. (Lessons from the history)