Rdf Based User Interfaces


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This paper presents from a theoretical point of view the idea of having web User Interface components that are fully described via RDF. Also, we offer a close look on the possibility of generating these components by a MDA framework starting from their RDF description as a model. The final part of the paper settles some future directions for both RDF and MDA and presents some conclusions regarding this

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Rdf Based User Interfaces

  1. 1. RDF based User Interfaces Ungureanu Vlad-Costel1 and Honciuc Irina1 Computer Science Faculty, ”Al. I. Cuza” University of Iasi Software Systems Engineering specialization Abstract. This paper presents from a theoretical point of view the idea of having web User Interface components that are fully described via RDF. Also, we offer a close look on the possibility of generating these components by a MDA framework starting from their RDF description as a model. The final part of the paper settles some future directions for both RDF and MDA and presents some conclusions regarding this approach. 1 Introduction If you have ever used a search engine then you probably know that the results of a search are not always what you where looking for. Not that the search engine didn’t do a good job, but rather the page you ended up at didn’t contain the information you where searching for. To give you an example, let’s say I typed ”James Cameron Avatar Trailer” in Google [10]. The search returned 2.800.000 results, out of which only the first two links on page one actually led to pages containing the actual trailer for the movie. The other three or four just contained the specified words. Now, imagine you had an option in Google to enable it to show you only those pages that actually had a media component that could display the trailer and that component was correctly bound to ”James Cameron Avatar” trailer, seen as a resource on a major social network (for example). To further refine the search you could, theoretically, ask Google to find only those pages that also had a component for a list of links, representing the cast, a component for rating, and a component for a large chunk of text all correctly bound to the previously named resource. Let’s consider another example in which you were fortunate enough to catch on film a happy moment in your life and, of course, you want to share it with the rest of the world, with the help of a social network. What if, instead of going over the huge list of links Wikipedia [15] provides in order to find a social network site that allows movies upload, you could tell the search engine to look for those social network sites that have an upload component and a movie gallery component on them. Of course people that have been socializing over the web for a long time know exactly where to go, but new users (old people, teenagers, people from third world countries) might want a little help adjusting to the magnitude of the World Wide Web.
  2. 2. 2 Ungureanu Vlad-Costel and Honciuc Irina One last example of this Interface Based Word Wide Web would by repre- sented by the existence of a specialized framework that could either create a desired user interface based on abstract description, while holding the seman- tics intact, or creating a user interface for a certain service based on the same principle. Based on the concepts presented in the previous examples we will discuss the technologies and concepts that could help us shape this special kind of Web, re- ferring to: User Interfaces (UI) as resources, Resource Description Format (RDF) as an abstract means for describing the interfaces, Model Driven Architecture (MDA) as architectural pattern that would allow UI generation based on some abstraction and finally to some examples on how all this could be achieved (at least on a theoretical level). 1.1 Motivation You could consider this as a manifest for the importance of User Interface, but the argument we present in this paper makes a clear point. It so happens that most people are ”wired” in such a way that, when they encounter something new they judge it by the way it looks. This does not mean people are shallow, but rather that they are adapted to get involved with only the things that appeal to them. As an example consider the following situation: will a person buy a suit that he/she thinks is very ugly only because it is cheap, practical and has a high quality? No, any market researcher will tell you that most people will buy the suit that they like the most regardless of the previously mentioned qualities, this is why we have Marketing. It becomes our concern when we want to promote a service in the web, not to trick people in visiting our web page, but rather to keep the user interested until we can present the functionality of a good looking application. This is why User Interface plays a immense role in getting users to use your application rather than look for something else. 2 User Interfaces as Resources Since we already mentioned that the Interface Based World Wide Web, we should put an emphasis on the subject. At the moment we have several distinct views over the web that try to put some sort of order in the multitude of resources, services, and information the web is made up of. We could say that the web is a repository for various documents, movies and images and we would not be far from the truth. Most of the web is centered around sharing information like news, facts, research, personal information with the rest of the world. In order to use this specific type of web you have to be able to search it based on key words that you think are contained in web pages, regardless of what they mean (their semantics). Another way the web could be seen is as a provider of services. You find the service you need, like e-mail, organizer, on-line shop or even more complex applications, you create an account, pay a fee if required and you can use all
  3. 3. RDF based User Interfaces 3 these services without downloads, installations, costly hardware upgrades. In order to use this type of web you need to have the required third party software (browser, plug-in, runtime environments) and a way to locate a certain service on the web. While most third party software is free the real problem is locating the service you desire. Ever tried typing ”mail” in your search engine? Locating the necessary web mail service can prove rather difficult when you can chose from more than 544.000.000 results. And of course there is the social web, a place where people gather to share their unique personalities, thoughts, opinions [11]. The social web provides the mean to find and get to socialize with people form any part of the world, any race, culture or language, braking the barriers of space and prejudice. But, as previously stated finding the right social site for your needs might prove a little too difficult, making all that socializing not that tempting. What if there was another way to see the web, a way that does not change anything in the present structure, but rather extends the semantics of the web. What if a piece of information, a service, or a social entity was also defined by the functionality it literally posses or exposes? We are referring to a way which allows for the actual user interface components to be described in terms of semantics and functionality, like the media component we spoke of previously. Such a web would then be based on the functionality it can offer the user (for example: digital signatures for the company email) or the functionality it provides for it’s user (for example: social networks based on image galleries like ”Lumea e Mica” [13] or ”Hi5” [12]). We will try to describe the attributes of a Interfaces Based Web in order to provide a definition for it. First, the perception of the interface should change into seeing components as actual resources. For this, an interface should hold some value, in order to quantify the components importance inside a page. The value of the component could be given by: – functionality: what functionality it exposes compared to other similar compo- nents. For example an upload movie component that allows multiple format types; – complexity: while complexity is sometimes a good thing, most of the time a heavy function component is both slow and rather hard to use. A simple component with complex functionality should be ranked higher; – technology: the technology used to generate the component should count in terms of speed, performance and the services it can encapsulate. Some technologies better suited for image galleries while others may have higher performance in handling multiple parallel Ajax requests; – related components: while a certain component might offer exactly what is expected of it, the other components of a page might lack many desired features. For example: an organizer that has a drag and drop calendar but has a limited address book, no alerts and only allows for 20 characters of details for each planed activity. Now that we have covered the importance of the components we should focus on the request, or more precisely the people that would be interested in
  4. 4. 4 Ungureanu Vlad-Costel and Honciuc Irina user interface components. The main issue is getting people to care about the components found in the pages they visit. In this case the people might care (and they actually do) about some of these factors: – simplicity: a service that does a great job after 30 minutes of page navigation is a very poor service; – features: aside from actual content (which is rarely the main concern) the features held in the page make the biggest impact. For example: a news site with the best news ever, with the best graphics ever and with no search is almost useless; – design: while for constant users of a service this doesn’t mean a lot, for new users the design is crucial. Take into consideration ”Craig’s List”’s [14] previ- ous design that chased away a lot of people. Several features seem mandatory out of which we can name: links to all main pages from each page and paging for more that 10 items. We can conclude that user interface components might hold a value and that higher ranking components might be more desirable than lower raking ones. With this in mind we are ready to give a definition to the Interface Based World Wide Web: the web in which components hold a value based on the qualities that the users considered most important and in which navigation and usage depend on the given value of the interface. As complicated as it might sound a shorter version should be sufficeint: the web in which the UI matters. 3 Resource Description Framework RDF (Resource Description Framework) represents a method of describing and modeling information about web resources [6, 9]. In RDF, the statements about web resources respect the subject-predicate-object format. This is also called a RDF triple. The subject refers to the resource, and the predicate denotes at- tributes of the object or expresses the relations between the subject and the object. The object is the resource that is referred by the predicate or it en- capsulates a value. For example, the statement ”Surrealism is a current.” can be expressed by a RDF triple in which the subject is ”Surrealism”, the predi- cate ”is a” denotes ”belongs to” and expresses the relation between the subject (surrealism) and the object (painting current). Both the subject and the object of the triple are resources that can be found at a specific URL. The predicate is also a resource that has a URL and describes a relationship. Note that the object could also be a blank node, in this case we don’t know what is the value, but we know it exists. We can state that a collection of RDF triples form a labeled, directed graph so we could look at a future (web or webs) as a larger graph formed by RDF triples. The labels on this graph edges are actualy the predicates in the triples. RDF has multiple serialization formats. The most common is the XML for- mat, but there are also Notation 3 or N3, Turtle and N-Triple formats. A simple example of a RDF triple expressed in XML format is listed below:
  5. 5. RDF based User Interfaces 5 RDF fragment in XML format <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about="http://en.wikipedia.org/wiki/Ren%C3%A9_Magritte"> <painting:currents>Surrealism<painting:currents> </rdf:Description> </rdf:RDF> The example above states that the ”painting current” attribute of the resource at http://en.wikipedia.org/wiki/Ren%C3%A9_Magritte is Surrealism. RDF is also a key element in semantic web. The RDF notation is supposed to provide ”a formal description of concepts, terms, and relationships within a given knowledge domain.” [7] The main idea that describes a semantic web is that information is linked at a global scale, forming a large database that offers an eficient way of retrieving relevant data about anything. [8] The RDF is like a building block in semantic web because it offers the possibility of describing data and associate an actual meaning (a semantic) to it. 4 Model Driven Architecture The objective of the Model Driven Architecture [4, 5] is to generate code for soft- ware applications starting from abstract specifications offered as models. MDA is used to develop, compare, verify and transform models (UML, XML) or meta- models (CWM - ”common warehouse model”). The architecture of a software application is model driven if: – the software application can create and modify models and metamodels; – the models can be verifyed against the modeling language; – the models can be coneverted to metamodels and backwards; – there can be represented relationships between models (inheritance, multi- plicity, etc.); – starting from the models and metamodels we can obtain a part of another application or even an application. There are some steps that apply in order to obtain an application that has a model driven architecture: – describe each aspect of the application: logic, functionality, persistency, ob- jects, interactions; – after obtaining complete specifications, a modelling tool is used to create the model of the application; this step also includes setting the relationships between objects and describing the application logic; – after the model is created, a MDA tool is used (any application or frame- work that can generate code starting from a model) to obtain a part of the application or the whole application); – after verifying the correctness of the generated code (its sintax), the appli- cation is finalized by adding the code that couldn’t be generated from the model, such as actions and navigation rules.
  6. 6. 6 Ungureanu Vlad-Costel and Honciuc Irina MDA has some important advantages, such as: – it’s easy to integrate with programming, software engineering and struc- ture standards because any portion of generated code can have a predefined shape, reflecting the actual rules and necesities; – we can reuse parts of the application by inserting the model we used in another application’s model; – the developing time is decreased because a large part of the code is auto- matically generated from the model; – it avoids repetivive code like ”user interface code” (especially for web/enterprise applications) MDA has also some disadvantages. Although there are unchanged standars and concepts, MDA depends also on some less theoretical aspects. For example, the lack of a language that can model actions (like xtUML which is just pure theoretical) limits the possibilities of generating application code for actions and navigations rules. Also, when integrating with databases or persistency models, a model driven architecture is hard to adapt to changes in schemas or other structures because the code generation is done starting from a statical model. Also, in order to work with MDA it’s necessary to have strong knowledge in programming languages, databases and persistency, UML tools, etc. 5 A RDF-UI Framework In order to describe the development of an Interface Based World Wide Web we can take a step by step approach into how this would be implemented. We have seen that RDF offers a way to abstractly describe any resource we want. An UI should make no exception from this, so the first step would be describing a certain UI component with the help of RDF. While there are many vocabularies for RDF none of them can properly serve in describing an interface. At the same time it is not the purpose of this paper to propose such a vocabulary, so keeping that in mind, we will exemplify a possible RDF description of an interface: RDF description for an interface <rdf:component rdf:url="link_to_page_containing target_component"> <rdf:description rdf:about="#ui_componet_name" > <rdf:association rdf:resource="#semantic_resource" /> <rdf:type rdf:media="movie_clip_upload"/> <rdf:media_format rtf:format="avi" /> <rdf:media_format rtf:format="mvk" /> <rdf:media_format rtf:format="mpeg" /> </rdf:type> <rdf: property rdf:size="10" rdf:measure="mb"/> <rdf:description> </rdf:component>
  7. 7. RDF based User Interfaces 7 The RDF example above describes a user interface named ”ui component name” that has the type ”movie clip upload” and can be found at the specified URL address. Further more the upload components is known to support three specific formats for clips not larger than 10MB. If you are looking for a video share site with support for .MKV format then this component is the one you need. The next step is to describe the referenced component is such a way that a MDA framework could interpret it and generate the desired component. Note that with the definition of a suitable RDF vocabulary the first step could be applied to the existing web with little effort. At the same time it would prove more efficient to generate the component based on the same RDF file, since the generated component will encapsulate all the elements of the description thus adding reliability to the Interface Based World Wide Web. RDF description for a component <rdf:ui rdf:ui_component="ui_component_name"> <rdf:ui_element rdf:entity="entity_that_encapsulate_movie_upload" <rdf:ui_element rdf:ui_type="file_upload" rdf:field="file_field_in_entity" /> <rdf:ui_element rdf:ui_type="button" rdf:action="method_in_entity" /> </rdf:ui> Using this abstract description a MDA framework could generate a ”file upload” as an input text field followed by a ”browse button”. The selected file would be associated with a file object in the specified entity. It would also generate another button that will have associated the upload method also defined in the entity. The third step would be to add the component to a web page and to associate the RDF to that page. Even though the MDA framework is not to be neglected in the integration of RDF with UI, the process seems simple and practical. Regardless of the implementation methods and technology used, the MDA framework based on the RDF description would provide a multitude of benefits to this approach out of which the most important are: – reducing development time because new application would use already cre- ated components, while the developers would only need to develop compo- nents for the new functionality; – continuity in usage methods, design and functionality over an entire web site or web application; – the possibility of using various technologies that best suite the functionality exposed in the UI. For example a PHP component for the picture gallery and a Java component for uploading and encoding pictures; – adding semantic meaning to the information presented by the component with the help of RDF. For example, the RDF could present the service the component provides, the information that is presented in the component and even if other entities have recommended it, for its high value.
  8. 8. 8 Ungureanu Vlad-Costel and Honciuc Irina 6 Further development We proposed a model in which an abstraction could describe a UI component and could facilitate it’s generation by a MDA framework, so we can now go deeper into the subject and talk a little about the technical challenges this approach would represent. RDF is now beginning to receive more attention even though the specifica- tions were finalized five years ago. Of course, none of the major search engines base their searches on this format and it may still take a while before this could become a key feature. On it’s own, RDF proves to be powerful and flexible, but in the current context it may allow faulty descriptions of the UI components both in terms of semantics and logic. For example you could describe a user interface like in the previous example as a cosmetic product as long as RDF remains lacked of any measure of control. The last point about RDF challenges refers to the query language that lacks the simplicity and power of the stan- dard SQL (joins, unions, views, procedures, agregates, etc.,). In time, solutions for all this problems may be provided as more and more people put effort into development. MDA has seen it’s first steps several times until now and it still lacks the maturity and the standardization that a good architecture requires. Several at- tempts have been made to raise the MDA standards, some even being suited for commercial use [1, 2]. Even so, dynamic generation of components based on highly abstractions (like XML and similar formats) are still in a theoretical stage [3]. MDA still has a long way to go before it can facilitate RDF based UI, but the possibilities seem promising enough to make it worth the effort. 7 Conclusions Starting form a technological point of view, the Web is not yet ready to adopt the RDF based User Interface, but from what we have seen this changes might prove a great step forward for the enhancement of the user experience. From a theoretical point of view this approach promises to facilitate the development process for most applications and the association of semantics to actual compo- nents. Several emerging technologies provide a good starting point, with some minor problems that can be easily overcome. The web can benefit from the appearance of a new perspective in which visual components play a major role both in functionality and in structure, as the UI can describe itself, the content it has and based on this description it can also generate itself using the technology that you choose. Last, but not least, the association of two technologies that are currently at the beginning of their evolution can only prove constructive for both of them. As a personal opinion, we believe that such a Web would become easier to use since the exact functionality you need in a web page may be only a search away.
  9. 9. RDF based User Interfaces 9 References 1. Andromeda, http://www.andromda.org/ 2. JMatter, http://jmatter.org/ 3. Frasinaru, Cristian; Ungureanu, Vlad-Costel: ”A generic component approach for dynamic generation of user interfaces”, 2009, RoCHI Conference. 4. http://www.omg.org/mda 5. http://www.ibm.com/developerworks/rational/library/3100.html 6. http://en.wikipedia.org/wiki/Resource_Description_Framework 7. http://en.wikipedia.org/wiki/Semantic_web 8. http://infomesh.net/2001/swintro/ 9. http://profs.info.uaic.ro/~busaco/teach/courses/wade/presentations/ web03RDF-ResourceDescriptionFramework.pdf 10. http://www.google.com 11. http://en.wikipedia.org/wiki/Social_network 12. http://hi5.com/ 13. http://www.lumeaemica.ro/ 14. http://www.craigslist.org/about/sites 15. http://en.wikipedia.org/