OK Juanjo That should work - as later stated in the definition there needs to be an explicit or implicit identification of event object from data Meaning that (taking your example of a DB record) The event type (name of the event) - could either come from some column\field in the record OR the name of the table (metadata) is the event type for all records. In both cases these still would be data elements so your explanation below I think covers this. On top of that though - we would need someone to explicitly 'map' the appropriate data element to the name of the event OR in some cases we could implicitly do this. Guy Sharon Manager Event-based Middleware & Solutions Group Event-based Middleware & Solutions phone : +972 4 8296587 mobile : +972 54 6976417 address : IBM R&D Labs in Israel, Haifa University Campus, Mount Carmel, Haifa, 31905, Israel email : guysh at il.ibm.com From: Juanjo Hierro <jhierro at tid.es> To: fiware-data at lists.fi-ware.eu Date: 14/06/2011 17:30 Subject: Re: [Fiware-data] Tentative definition of basic concepts: data, context and events Sent by: fiware-data-bounces at lists.fi-ware.eu On 14/06/11 15:54, Guy Sharon wrote: My only comment is regarding events I think our statement can be stronger about how an event object looks like - that we know what we want as a basic and things can be added ontop. The very basic is that an event object must have a type name. (one of the major distinctions from data), e.g rightMouseClick, buyStock Note that a "data element" has an EntityId as well as a Type name. So the type name you are asking for is there: matches the name of the type linked to the data element. The properties (or better yet use what we already defined ... data element) could be multiple ones BUT the basis must contain like you have written the detection time which is the time the event object was created. With these two pieces of information we can start creating event processing logic - without these you can't. Data elements have a set of properties, but I believe we should not force data elements to have a property corresponding to "detection time" if we want to process them as events. We want to be able to read a given data element (as an example, as result of retrieving a data record from a data base) and be able to push it to the CEP GE or the Publish/Subscribe Broker GE. This would mean adding a timestamp actually, but that would go as a part of a sort of "header" of the event object wrapping the data element which would be created by the CEP GE internally to ease event processing. That's why I have declared that event objects are made of data element plus some associated properties relevant for event processing (timestamp and maybe others we may find useful). I feel like we should precisely add that those event objects will be created at the time a data element arrives to the CEP GE (and I would add ven to the Publish/Subscribe Broker GE). We don't need to attach a type name as part of the header in the event object wrapping a data element because the data element structure already contains the type name. I believe that the descriptions I provided were compatible with those you provided initially. I just wanted to formulate them in a way that: any sort of data elements could be transformed into event objects (would be just a matter of attaching info relevant to event processing) the definition of data elements and context elements allow us to go for a model which is close or compliant to the model defined in the OMA standard Please think about it carefully and with an open mind, not having a concrete product in mind. Best regards, -- Juanjo Guy Sharon Manager Event-based Middleware & Solutions Group Event-based Middleware & Solutions phone : +972 4 8296587 mobile : +972 54 6976417 address : IBM R&D Labs in Israel, Haifa University Campus, Mount Carmel, Haifa, 31905, Israel email : guysh at il.ibm.com From: Juanjo Hierro <jhierro at tid.es> To: "fiware-data at lists.fi-ware.eu" <fiware-data at lists.fi-ware.eu> Date: 14/06/2011 14:00 Subject: [Fiware-data] Tentative definition of basic concepts: data, context and events Sent by: fiware-data-bounces at lists.fi-ware.eu Dear all, As you know, one of the action points from our last confcall had to do with providing a tentative definition of basic concepts in our chapter like data, context and event. Please find the document I have produced on the matter at: https://forge.fi-ware.eu/docman/view.php/9/141/Notes+and+Thoughts+on+definition+of+data-context-event.doc Just in case you believe it would be more easy to run a discussion via email following this email, I have attached the text of this document below. Hope you find it useful. Your feedback is welcome. Best regards, -- Juanjo 1. Motivation This document intends to provide a precise description of some basic concepts like data, context and events in FI-WARE. These concepts are fundamental in the description of the Data/Context Management platform in FI-WARE and the way applications are developed based on that platform. Contents of this document will be considered as baseline for a post to publish in our Data/Context Management blog in www.fi-ware.eu ( http://data.fi-ware.eu) 2. Definition of Data Data refers to information that is produced, generated, collected or observed that may be of relevance for processing, further analysis or information and knowledge generation. Essentially refers to information relevant to applications. Data in FI-WARE has associated a data type and a value. FI-WARE will support a set of built-in basic data types like in most programming languages. Values linked to these basic data types supported in FI-WARE are referred as basic data values. So we have the notion of the integer basic data type and basic values like ?2?, ?7? or ?365? that belong to the integer basic data type. A data element refers to data whose value is defined as a sequence of one or more <name, type, value> triplets referred as data element attributes, where the type and value of each attribute is either linked to a basic data type and a basic value or is linked to the data type and value of another data element. Note that each data element has an associated data type as any data in the system. This data type determines what concrete sequence of attributes characterizes that data element. There may be meta-data (also referred as semantic data) linked to attributes in a data element. However, existence of meta-data linked to a data element attribute is optional. Any data element has an entity in any FI-WARE Instance and, as such, it has an associated EntityId which universally and unequivocally indentifies the data element among the whole set of existing data elements. The basic concepts introduced so far are represented in Figure 1. Figure 1. Basic Model for Data A cornerstone concept in FI-WARE is that data elements are not tied to a specific format. They can be transferred as an XML document or in some sort of efficient binary representation and then be stored in a Relational Database or as entries in a noSQL data base like MongoDB. 3. Definition of Context Context in FI-WARE is represented through context elements. A context element is just a particular case of data element. However, there may be some attributes as well as meta-data associated to attributes that we may define as mandatory for any type of context element in FI-WARE. 4. Definition of Event An event is an occurrence within a particular system or domain; it is something that has happened, or is contemplated as having happened in that domain. The word event object is used to mean a programming entity that represents such an occurrence (event) in a computing system [EPIA]. Events are represented as event objects within computing systems to distinguish them from other types of objects and to perform operations on them, also known as event processing. It is common to refer to event objects simply as events. In FI-WARE, event objects are defined as a data element to which a number of standard event object properties (similar to a header) are associated. The concrete set of standard event object properties in FI-WARE is still to be defined but we may anticipate that one of these properties would be the time at which the event object was created. The data element and the standard properties linked to an event are used to describe, as mentioned above, something that has happened or is contemplated as having happened in a given domain. A context event The relationship (or difference) of the terms data and event is continuously debated. One summary of the philosophical and technical aspects of such debates is included in the background section of [Grove 06] with several references to the different opinions and definitions. For the purpose of FI-WARE and in specifically of the Context and Data Management Generic Enablers, we need to distinguish between the semantic level and the technical level of such a relationship that FI-WARE wishes to adopt, communicate, through its interfaces, and implement. Semantically speaking, the term data subsumes the term event meaning that some data can be semantically interpreted as events. From a technical perspective data is the way information is communicated in FI-WARE and it needs to be explicitly or implicitly identified as an event object and vice versa for processing the data as event. Este mensaje se dirige exclusivamente a su destinatario. Puede consultar nuestra política de envío y recepción de correo electrónico en el enlace situado más abajo. This message is intended exclusively for its addressee. We only send and receive email on the basis of the terms set out at. http://www.tid.es/ES/PAGINAS/disclaimer.aspx[attachment "jhierro.vcf" deleted by Guy Sharon/Haifa/IBM] _______________________________________________ Fiware-data mailing list Fiware-data at lists.fi-ware.eu http://lists.fi-ware.eu/listinfo/fiware-data Este mensaje se dirige exclusivamente a su destinatario. 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