1 On the other hand, several relational SQL extensions have been provided to handle XML data. It is to be recalled that its latest version, XQuery 1.1, supports tuple oriented stream manipulation with the help of windows clause. On one hand, XQuery, using the FLWOR expression, is extremely powerful in retrieving XML documents/ordered sequence of items/elements satisfying a condition with projection, selection, and join operators. It is important to note that the current XML based retrieval techniques can be: XML-based query language and SQL extensions. In essence, this is due to the retrieval techniques adopted in these readers which are XML-based as RSS is based on XML format. However, the data retrieval functionalities of the existing readers are restricted to very elementary operations such as searching based on text matching, keyword based filtering, and personalization. People use RSS readers/aggregators to aggregate feeds from the same or different sources rather than roaming site to site. Nowadays, the number of applications that use RSS is increasing. So, querying such complex and text oriented data has to consider both time retrieval and semantic information. (identical topics might be described differently, while different topics might be described using similar concepts). stated that on average 55% of the RSS feeds are updated within 1 h and (2) their contents are dependent on the authors’ style of writing and use of words, nouns, verbs, etc. RSS news items have two characteristics: (1) they are dynamic. RSS has been proposed to facilitate the aggregation of information from multiple and distributed web sources. Really Simple Syndication (RSS) is an XML-based family of web feed formats used to publish frequently updated contents such as blog entries, news headlines and podcasts, in a standardized format. In addition and in order to validate our proposal, we develop a prototype called EasyRSSManager that allows a user to formulate RSS query using our operators. We also provide a set of query rewriting and equivalence rules that would be used during query simplification and optimization. The provided operators are application domain specific and can be tuned according to the user preferences. ![]() In this paper, we aim to solve these issues by providing a dedicated RSS algebra based on semantic-aware operators which are capable of considering RSS characteristics. Existing XML query algebras are not fully appropriate to retrieve RSS news items mainly due to three reasons: (1) RSS document is text rich and its content is dependent on the wording and verification of the author, thus semantic-aware operators are needed (2) news items are dynamic and consequently time oriented retrieval is needed and (3) a news item may evolve through time, or overlap with other news items and hence identifying relationships between items is needed.
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