5/23/2014

Eclipse jsp the function fn:replace undefined

I am using maven2 and Eclipse Kepler. And when I run "maven clean", the code compiles successfully and shows the message "BUILD SUCCESS". But I get the red squiggly underlines under fn:replace call in one .jsp file.

I checked the pom.xml file, and found it include the reference to JSTL as below:
<dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
            <scope>runtime</scope>

</dependency>

After Google the Internet, I found the solution, which is to include the following line in the .jsp file
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

and run clean project, then the error is fixed.

5/20/2014

Creation of Amazon EC2 Key Pairs

You can use both Amazon EC2 console and command line "ec2-create-keypair" to create a Key pair.

The details is in Amazon AWS web site: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-key-pairs.html

Amazon EC2 command ec2-run-instances error client.invalidamiid.notfount

I was using the command-line ec2-run-instances to create an EC2 instance. However I kept getting the following error message:

Client.InvalidAMIID.NotFound: The image id '[ami-xxxxxxxx]' 
does not exist Error starting (256):

The solution is that I need specify the region using the option --region --region ap-southeast-1 


One example is



5/15/2014

Design Patterns for Large-Scale Real-Time Learning

A presentation slides from Sean Owen

http://qconlondon.com/dl/qcon-london-2014/slides/SeanOwen_DesignPatternsForLargeScaleRealTimeLearning.pdf

Lambda Architecture

The Lambda Architecture is proposed by Nathan Marz, which is a generic, scalable and fault-tolerant data processing architecture. 

There are some useful resources online:
1. The first Lambda Architecture post wrote by Nathan Marz
http://www.databasetube.com/database/big-data-lambda-architecture/

2. An simple introduction.
http://lambda-architecture.net/

3. Lambda Architecture: A state of the art
http://www.datasalt.com/2014/01/lambda-architecture-a-state-of-the-art/

4/28/2014

DLMS/COSEM

DLMS or Device Language Message Specification and COSEM or Companion Specification for Energy Meeting is a specification that specifies an interface model and communication protocols for data exchange with metering equipment. And DLMS/COSEM has been adopted by the IEC TC13 WG14 into the IEC 62056 series of standards.
COSEM specifies the interface model, which provides a view of the functionality of the meter as it is available at its interface(s). The interface consists of attributes and methods, where the attributes values represent all the data in meters and the methods describe the allowable operations to be performed on the attributes.
DLMS is an application layer protocol that defines how the data can be accessed and transported.
The DLMS/COSEM specification is document in 4 “books”.
  • The Blue book “COSEM – Identification System and Interface Classes” specifies the interface model
  • The Green book “DLMS/COSEM – Architecture and Protocols” specifies the architecture and the protocols with DLMS on top, for the various media specific communication profiles. The communication media includes RS-232, RS-485, PSTN, GSM, GPRS, IPv4 PPP and PLC.
  • The Yellow book specifies conformance test plans for COSEM object interface model.
  • The White book is a glossary of terms.