Modified: zest/site/content/java/develop/what-is-cop.html URL: http://svn.apache.org/viewvc/zest/site/content/java/develop/what-is-cop.html?rev=1689843&r1=1689842&r2=1689843&view=diff ============================================================================== --- zest/site/content/java/develop/what-is-cop.html (original) +++ zest/site/content/java/develop/what-is-cop.html Wed Jul 8 11:08:41 2015 @@ -66,20 +66,20 @@ })(); </script> - </head><body><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="logo"><a href="index.html"><img src="images/logo-standard.png" /></a></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="top-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="index.html#home">Qi4j</a></span></dt><dt><span class="section"><span xmlns="" href="intro.html">Introduction</span></span></dt><dt><span class="section"><a href="tutorials.html">Tutorials</a></span></dt><dt><span class="section"><a href="javadocs.html">Javadoc</a></span></dt><dt><span class="section"><a href="samples.html">Samples</a></span></dt><dt><span class="section"><a href="core.html">Core</a></span></dt><dt><span class="section"><a href="libraries.html">Libraries</a></span></dt><dt><span class="section"><a href="extensions.html">Extensions</a></span></dt><dt><span class="section"><a href="tools.html">Tools</a></span></dt><dt><span class="section"><a href="glossary.html">Glo ssary </a></span></dt></dl></div></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="sub-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="intro.html#highlights">Highligts</a></span></dt><dt><span class="section"><a href="introduction-background.html">Background</a></span></dt><dt><span class="section"><span xmlns="" href="what-is-cop.html">What is COP?</span></span></dt><dt><span class="section"><a href="what-s-an-object-anyway.html">Whatâs an Object anyway?</a></span></dt><dt><span class="section"><a href="state-modeling.html">Qi4j and state modeling</a></span></dt><dt><span class="section"><a href="related.html">Related publications & projects</a></span></dt></dl></div></div><div class="section" title="What is COP?"><div class="titlepage"><div><div><h3 class="title"><a id="what-is-cop"></a>What is COP?</h3></div></div></div><p>We found this very well written blog entry on the Internet, which very well describ es what Composite Oriented + </head><body><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="logo"><a href="index.html"><img src="images/logo-standard.png" /></a></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="top-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="index.html#home">Zestâ¢</a></span></dt><dt><span class="section"><span xmlns="" href="intro.html">Introduction</span></span></dt><dt><span class="section"><a href="tutorials.html">Tutorials</a></span></dt><dt><span class="section"><a href="javadocs.html">Javadoc</a></span></dt><dt><span class="section"><a href="samples.html">Samples</a></span></dt><dt><span class="section"><a href="core.html">Core</a></span></dt><dt><span class="section"><a href="libraries.html">Libraries</a></span></dt><dt><span class="section"><a href="extensions.html">Extensions</a></span></dt><dt><span class="section"><a href="tools.html">Tools</a></span></dt><dt><span class="section"><a href="glossary.htm l">Glossary </a></span></dt></dl></div></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="sub-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="intro.html#highlights">Highligts</a></span></dt><dt><span class="section"><a href="introduction-background.html">Background</a></span></dt><dt><span class="section"><span xmlns="" href="what-is-cop.html">What is COP?</span></span></dt><dt><span class="section"><a href="what-s-an-object-anyway.html">Whatâs an Object anyway?</a></span></dt><dt><span class="section"><a href="state-modeling.html">Zest⢠and state modeling</a></span></dt><dt><span class="section"><a href="related.html">Related publications & projects</a></span></dt></dl></div></div><div class="section" title="What is COP?"><div class="titlepage"><div><div><h3 class="title"><a id="what-is-cop"></a>What is COP?</h3></div></div></div><p>We found this very well written blog entry on the Internet, which very well describes what Composite Oriented Programming really is.</p><p>The article uses C# and a "show by example" approach to explaining COP, and this shows clearly that COP is not -Java specific, and although Qi4j was (to our knowledge) first to introduce the name, it applies across languages and +Java specific, and although Zest⢠was (to our knowledge) first to introduce the name, it applies across languages and potentially deserves one or more languages on its own.</p><p>The article is re-published here, as allowed by the <a class="ulink" href="http://msdn.microsoft.com/en-us/windowsmobile/bb264332.aspx"; target="_top">Microsoft Permissive License</a> , more recently known as <a class="ulink" href="http://www.opensource.org/licenses/MS-PL"; target="_top">Microsoft Public License</a>. The content below is NOT under the usual <a class="ulink" href="http://www.opensource.org/licenses/Apache-2.0"; target="_top">Apache License</a>.</p><p>We would like to thank Fredrik Kalseth for his explicit approval as well.</p><div class="section" title="Composite Oriented Programming"><div class="titlepage"><div><div><h4 class="title"><a id="_ulink_url_http_iridescence_no_post_composite_oriented_programming_aspx_composite_oriented_programming_ulink"></a><a class="ulink" href="http://iridescence.no/post/composite-oriented-programming.aspx"; target="_top">Composite Oriented Programming</a></h4></div></div></div><p>Iâve written a series of post on AOP lately (here, here and here), and in the last part I promised to tackle mixins and introductions in a future post. When I was doing my research for just that, I came cross a Java framework (just -humor me :p) called Qi4j (thatâs <span class="emphasis"><em>chee for jay</em></span>), written by Swedish Richard Ãberg, pioneering the idea of Composite +humor me :p) called Zest⢠(thatâs <span class="emphasis"><em>chee for jay</em></span>), written by Swedish Richard Ãberg, pioneering the idea of Composite Oriented Programming, which instantly put a spell on me. Essentially, it takes the concepts from Aspect Oriented Programming to the extreme, and for the past week Iâve dug into it with a passion. This post is the first fruits of my labor.</p><div class="section" title="OOP is Not Object Oriented!"><div class="titlepage"><div><div><h5 class="title"><a id="_oop_is_not_object_oriented"></a>OOP is Not Object Oriented!</h5></div></div></div><p>One of the things that Richard Ãberg argues, is that OOP is not really object oriented at all, but rather class -oriented. As the Qi4j website proclaims, "class is the first class citizen that objects are derived from. Not objects +oriented. As the Zest⢠website proclaims, "class is the first class citizen that objects are derived from. Not objects being the first-class citizen to which one or many classes are assigned". Composite oriented programming (COP) then, tries to work around this limitation by building on a set of core principles; that behavior depends on context, that decoupling is a virtue, and that business rules matter more. For a short and abstract explanation of COP, @@ -257,7 +257,7 @@ public interface ISubtraction : ICalcula posts. Iâve already implemented a prototype framework that supports the above examples, which builds on my <a class="ulink" href="http://www.iridescence.no/Posts/Implementing-an-AOP-Framework-Part-2.aspx"; target="_top">previously posted AOP framework</a>, and Iâll post the source code for that soon. If you want to dig deeper right now (and donât mind -a bit of Java), then I suggest you head over to the Qi4j website and poke about there. +a bit of Java), then I suggest you head over to the Zest⢠website and poke about there. <a class="ulink" href="http://rickardoberg.wordpress.com/"; target="_top">Richard Ãbergs blog</a> also provides great insight.</p></div></div></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="footer"><p> Copyright © 2015 The Apache Software Foundation, Licensed under the <a href="http://www.apache.org/licenses/"; target="_blank">Apache License, Version 2.0</a>. <br /><small>
Modified: zest/site/content/java/develop/what-s-an-object-anyway.html URL: http://svn.apache.org/viewvc/zest/site/content/java/develop/what-s-an-object-anyway.html?rev=1689843&r1=1689842&r2=1689843&view=diff ============================================================================== --- zest/site/content/java/develop/what-s-an-object-anyway.html (original) +++ zest/site/content/java/develop/what-s-an-object-anyway.html Wed Jul 8 11:08:41 2015 @@ -1,5 +1,5 @@ <?xml version="1.0" encoding="UTF-8" standalone="no"?> -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";><html xmlns="http://www.w3.org/1999/xhtml";><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Whatâs an Object anyway?</title><link rel="stylesheet" type="text/css" href="css/style.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.76.1" /><link rel="home" href="index.html" title="" /><link rel="up" href="intro.html" title="Introduction" /><link rel="prev" href="what-is-cop.html" title="What is COP?" /><link rel="next" href="state-modeling.html" title="Qi4j and state modeling" /> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";><html xmlns="http://www.w3.org/1999/xhtml";><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Whatâs an Object anyway?</title><link rel="stylesheet" type="text/css" href="css/style.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.76.1" /><link rel="home" href="index.html" title="" /><link rel="up" href="intro.html" title="Introduction" /><link rel="prev" href="what-is-cop.html" title="What is COP?" /><link rel="next" href="state-modeling.html" title="Zest⢠and state modeling" /> <!-- favicon --> @@ -66,7 +66,7 @@ })(); </script> - </head><body><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="logo"><a href="index.html"><img src="images/logo-standard.png" /></a></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="top-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="index.html#home">Qi4j</a></span></dt><dt><span class="section"><span xmlns="" href="intro.html">Introduction</span></span></dt><dt><span class="section"><a href="tutorials.html">Tutorials</a></span></dt><dt><span class="section"><a href="javadocs.html">Javadoc</a></span></dt><dt><span class="section"><a href="samples.html">Samples</a></span></dt><dt><span class="section"><a href="core.html">Core</a></span></dt><dt><span class="section"><a href="libraries.html">Libraries</a></span></dt><dt><span class="section"><a href="extensions.html">Extensions</a></span></dt><dt><span class="section"><a href="tools.html">Tools</a></span></dt><dt><span class="section"><a href="glossary.html">Glo ssary </a></span></dt></dl></div></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="sub-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="intro.html#highlights">Highligts</a></span></dt><dt><span class="section"><a href="introduction-background.html">Background</a></span></dt><dt><span class="section"><a href="what-is-cop.html">What is COP?</a></span></dt><dt><span class="section"><span xmlns="" href="what-s-an-object-anyway.html">Whatâs an Object anyway?</span></span></dt><dt><span class="section"><a href="state-modeling.html">Qi4j and state modeling</a></span></dt><dt><span class="section"><a href="related.html">Related publications & projects</a></span></dt></dl></div></div><div class="section" title="Whatâs an Object anyway?"><div class="titlepage"><div><div><h3 class="title"><a id="what-s-an-object-anyway"></a>Whatâs an Object anyway?</h3></div></div></div><p>In OOP the main idea is that we shoul d model our reality by creating Objects. Objects have state, and they have methods. + </head><body><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="logo"><a href="index.html"><img src="images/logo-standard.png" /></a></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="top-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="index.html#home">Zestâ¢</a></span></dt><dt><span class="section"><span xmlns="" href="intro.html">Introduction</span></span></dt><dt><span class="section"><a href="tutorials.html">Tutorials</a></span></dt><dt><span class="section"><a href="javadocs.html">Javadoc</a></span></dt><dt><span class="section"><a href="samples.html">Samples</a></span></dt><dt><span class="section"><a href="core.html">Core</a></span></dt><dt><span class="section"><a href="libraries.html">Libraries</a></span></dt><dt><span class="section"><a href="extensions.html">Extensions</a></span></dt><dt><span class="section"><a href="tools.html">Tools</a></span></dt><dt><span class="section"><a href="glossary.htm l">Glossary </a></span></dt></dl></div></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="sub-nav"><div xmlns="http://www.w3.org/1999/xhtml"; class="toc"><dl><dt><span class="section"><a href="intro.html#highlights">Highligts</a></span></dt><dt><span class="section"><a href="introduction-background.html">Background</a></span></dt><dt><span class="section"><a href="what-is-cop.html">What is COP?</a></span></dt><dt><span class="section"><span xmlns="" href="what-s-an-object-anyway.html">Whatâs an Object anyway?</span></span></dt><dt><span class="section"><a href="state-modeling.html">Zest⢠and state modeling</a></span></dt><dt><span class="section"><a href="related.html">Related publications & projects</a></span></dt></dl></div></div><div class="section" title="Whatâs an Object anyway?"><div class="titlepage"><div><div><h3 class="title"><a id="what-s-an-object-anyway"></a>Whatâs an Object anyway?</h3></div></div></div><p>In OOP the main idea is t hat we should model our reality by creating Objects. Objects have state, and they have methods. Methods in an object are used to operate on the internal state and understands the domain that is being modeled.</p><p>By contrast, in procedural programming the focus is on algorithms, which can use several data structures to perform some task. The focus is on what is going on, rather than the "objects" involved.</p><p>With OOP it becomes more difficult to "read" algorithms, as they are spread out in many objects that interact. With procedural programming it becomes difficult to encapsulate and reuse functionality. Both represent extremes, neither of @@ -84,7 +84,7 @@ there will be an interface, and for each This mixin can be specific for that composite implementation, or it can be generic and reused. The key point is that it is the OBSERVER of the object, meaning, the algorithm, that gets to decide what the object should be able to do.</p><p>This is the same in real life. I donât get to decide how I communicate with you. I have to use english, and I have to use email, and I have to send it to a specific mailing list. It is the algorithm of the interaction between us, the -Qi4j dev mailing list, that has set these rules, not <span class="strong"><strong>I</strong></span> as a participant in this interaction. The same should, +Zest⢠dev mailing list, that has set these rules, not <span class="strong"><strong>I</strong></span> as a participant in this interaction. The same should, obviously, be the case for objects.</p><p>So, with the understanding that algorithms should define roles for collaborating objects, and objects should then implement these in order to participate in these algorithms, it should be trivial to realize that what has passed for OOP so far, in terms of "class oriented programming", where this role-focus of objects is difficult to achieve, if not @@ -92,7 +92,7 @@ even impossible, is just plain wrong. I designated as "coordinator", which then delegates to a number of other objects in order to implement the various roles. This "solution", which is caused by this fundamental flaw in "class oriented programming", is essentially a hack, and causes a number of other problems, such as the "self schizophrenia" problem, whereby there is no way to tell where the -object really is. There is no "this" pointer that has any relevant meaning.</p><p>The Composite pattern, as implemented in COP and Qi4j, gets around this by simply saying that the composite, as a +object really is. There is no "this" pointer that has any relevant meaning.</p><p>The Composite pattern, as implemented in COP and Zestâ¢, gets around this by simply saying that the composite, as a whole, is an object. Tada, we now have a "this" pointer, and a coherent way to deal with the object graph as though it was a single object. We are now able to get back to the strengths of the procedural approach, which allows the implementer of the algorithm to define the roles needed for the algorithm. The roles can either be specific to an @@ -100,7 +100,7 @@ algorithm, or they can be shared between algorithm is not too tightly encoded in the composites, thereby making the algorithms more reusable, and making it less necessary to read composite code when trying to understand algorithms. The assumption here is that we are going to write more algorithms than composites, therefore it has to be easy to ready algorithms, and only when necessary dive down into -composite code.</p><p>When talking about Composites as Objects in Qi4j it is most relevant to look at Entities, since these represent physical +composite code.</p><p>When talking about Composites as Objects in Zest⢠it is most relevant to look at Entities, since these represent physical objects in a model, rather than algorithms or services, or other non-instance-oriented things.</p><p>If Entities should implement roles, via mixins, in order to interact with each other through algorithms, then the majority of their behaviour should be put into those role-mixins. These are exposed publically for clients to use. However, the state that is required to implement these roles should not be exposed publically, as they represent @@ -132,7 +132,7 @@ general allow our role-oriented approach generally reusable, and the state interfaces are usually reusable. This minimizes the need for us to go into the mixin code and read it. If we have read the mixin code once, and the same mixin is reused between objects, then this makes it easier for us to understand it the next time we see it being used in another algorithm.</p><p>To summarize thus far, we have looked at why OOP so far has not worked out, why this is the case, and how COP deals -with it, and how we can implement a better solution of Entities using Qi4j. All is well!</p><p>The next step is to start using these Entities in algorithms. Algorithms are usually stateless, or at least they donât +with it, and how we can implement a better solution of Entities using Zestâ¢. All is well!</p><p>The next step is to start using these Entities in algorithms. Algorithms are usually stateless, or at least they donât have any state that survives the execution of the algorithm. There is input, some calculation, and then output. In other words, our notion of services fit perfectly here!</p><p>Algorithms, then, should(/could?) be modeled using services. If an algorithm needs other algorithms to compute something, that is, if a service needs another service to do something, we can accomplish this using dependency @@ -162,14 +162,14 @@ would need to get the three objects invo selected item in a list, and "TaskExecutor to" could be a user designated from a popup dialog. These three are then taken by the context and used to execute the "delegate" interaction, which performs all the steps necessary.</p><p>The interaction method "delegate" is testable, both with mocks of the input, and with specific instances of the various roles. The implementations are also testable, and if the same mixin is used over and over for the implementation, then -only one set of tests is needed for each role interface.</p><p>To summarize we have in COP/Qi4j a way to get the best from procedural and object-oriented programming. As we have seen +only one set of tests is needed for each role interface.</p><p>To summarize we have in COP/Zest⢠a way to get the best from procedural and object-oriented programming. As we have seen the functionality falls into three categories, the entities implementing objects, the services implementing interactions, and the user interface implementing the context. This also maps well to the ideas of ModelViewController, which in turn maps well to the new ideas from Mr Reenskaug (inventor of MVC) called DCI: Data-Context-Interaction. As a -side-effect of this discussion we have therefore also seen how COP/Qi4j can be used to implement DCI, which is an +side-effect of this discussion we have therefore also seen how COP/Zest⢠can be used to implement DCI, which is an important next step in understanding objects and their interactions, the fundamentals of which (I believe) are captured on this page.</p><p>Thatâs it. Well done if youâve read this far :-)</p><p>Comments and thoughts to qi4j-dev forum at Google Groups on this are highly appreciated. This is very very important topics, -and crucial to understanding/explaining why COP/Qi4j is so great! :-)</p></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="footer"><p> +and crucial to understanding/explaining why COP/Zest⢠is so great! :-)</p></div><div xmlns="" xmlns:exsl="http://exslt.org/common"; class="footer"><p> Copyright © 2015 The Apache Software Foundation, Licensed under the <a href="http://www.apache.org/licenses/"; target="_blank">Apache License, Version 2.0</a>. <br /><small> Apache Zest, Zest, Apache, the Apache feather logo, and the Apache Zest project logo are trademarks of The Apache Software Foundation.<br />
