gwagner's blog

Architectures for the Web of Things

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In the Web of Things (WoT), special communication networks composed of sensor nodes, actuator nodes and service nodes form the basis for new types of web applications, which are directly connected to the real world via sensors and actuators, and can be private, such as smart home apps, personal robotics apps and factory control applications, or public, such as air pollution monitoring systems and city parking management systems.

What does it need to be not only a good coder, but become a great app developer?

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If you want to become a great app developer, it's not sufficient that you master your favorite programming technologies. It's essential that you understand all basic concepts and techniques, not just in programming, but also in information management.

A programming (or software development) technology typically combines a programming language (such as JavaScript, Java or C#) with a framework/library for user interface and data storage programming (such as BackboneJS, JSF or ASP.NET MVC).

Defining and Using Classes in JavaScript

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The concept of a class is fundamental in object-oriented programming. Objects instantiate (or are classified by) a class. A class defines the properties and methods (as a blueprint) for the objects that instantiate it. Having a class concept is essential for being able to implement a data model in the form of model classes within a Model-View-Container (MVC) architecture.

JavaScript supports four types of basic data structures

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The four types of basic data structures supported by JavaScript are: array lists, maps, records and JSON tables. The following list provides a summary:

  1. Array lists, such as ["one","two","three"], are special JS objects called 'arrays', but since they are dynamic, they are rather array lists as defined in the Java programming language.

  2. Maps are also special JS objects, such as {"one":1,"two":2,"three":3}, as discussed below.

Expressing Date/Time Information with the <time> Element

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While date/time information items have to be formated as strings in a human-readable form on web pages, preferably in localized form based on the settings of the user's browser, it's not a good idea to store date/time values in this form. Rather we use instances of the pre-defined JavaScript class Date for representing and storing date/time values.

Storing database tables in JavaScript's Local Storage

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In most apps we have some form of data management where data is represented in tables such that table rows correspond to objects, anf the table schema corresponds to the objects' type. When building a front-end web app with JavaScript, the simplest approach for persistent data storage is using JavaScript's localStorage API, which provides a simple key-value database, but does not support database tables. So, the question is: how can we store and retrieve tables with Local Storage?

Why are associations so difficult to understand, not just for developers?

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Class diagram with a chair association between classes Committee and ClubMemberIn summary, the answer to this question is: because unlike the general concept of an object type or class, the general concept of an association, as defined by UML, does not have a direct computational counterpart, neither in common object-oriented (OO) programming languages, nor in SQL.


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