Caché

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Astronomers’ tools

5 years ago, on December 19, 2013, the ESA launched an orbital telescope called Gaia. Learn more about the Gaia mission on the official website of the European Space Agency or in the article by Vitaly Egorov (Billion pixels for a billion stars).

However, few people know what technology the agency chose for storing and processing the data collected by Gaia. Two years before the launch, in 2011, the developers were considering a number of candidates (see “Astrostatistics and Data Mining” by Luis Manuel Sarro, Laurent Eyer, William O’Mullane, Joris De Ridder, pp. 111-112):

Comparing the technologies side-by-side produced the following results (source):

TechnologyTime
DB213min55s
PostgreSQL 814min50s
PostgreSQL 96min50s
Hadoop3min37s
Cassandra3min37s
Caché2min25s

The first four will probably sound familiar even to schoolchildren. But what is Caché XEP?

Last comment 9 January 2019
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The following code walks a DOM using %XML.Node. It also prevents %XML.Writer to change whitespace. Run the code using the class method "test":


Class objectscript.walkDOM Extends %Persistent
{
    ClassMethod dfs(node As %XML.Node)
    {
        s entrynode=node.NodeId
        do {
        //element nodes with one whitespacetyped child are the ones we want to change
        if (node.NodeType=$$$xmlELEMENTNODE){
            s snode=node.NodeId     
            if (node.MoveToFirstChild())            
                {
                    i ('node.MoveToNextSibling()){
                        i (node.NodeType=$$$xmlWHITESPACENODE){
                            s node.NodeType=$$$xmlTEXTNODE
                            s node.NodeId=snode
                        }
                    }
            }
            s node.NodeId=snode     
        }   
        if (node.HasChildNodes()){
            d node.MoveToFirstChild()
            d ..dfs(node)
        }
        } while (node.NodeType'="" && node.MoveToNextSibling())
        s node.NodeId=entrynode
         
    }
     
    ClassMethod test()
    {
      set xml = "abcdefg"
     
      s reader=##class(%XML.Reader).%New()
      do reader.OpenString(xml)  
      set writer = ##class(%XML.Writer).%New()
      //do some magic
      d ..dfs(reader.Document)
       
      w !,"with indent=1:",!
      set writer.Indent = 1
      do writer.OutputToString()
      do writer.Document(reader.Document)
      w writer.GetXMLString()
      set writer.Indent = 0
      w !,"with indent=0:",!
      do writer.OutputToString()
      do writer.Document(reader.Document)
      w writer.GetXMLString()
    }
}

Here's a link to the code on GitHub: https://github.com/intersystems-community/code-snippets/blob/master/src/...

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InterSystems products (IRIS, Caché, Ensemble) already include a built-in Apache web server. But the built-in server is designed for the development and administration tasks and thus has certain limitations. Though you may find some useful workarounds for these limitations, the more common approach is to deploy a full-scale web server for your production environment. This article describes how to set up Apache to work with InterSystems products and how to provide HTTPS access. We will be using Ubuntu, but the configuration process is almost the same for all Linux distributions.

Last comment 25 December 2018
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Some weeks ago, I was reading a book by Stephen Hawking and Leonard Mlodinow, The Grand Design. At a certain point, trying to define why do we exist? , why do we use the models we use in physics?, ...those kind of things you know... they pointed at the Game of Life example invented by the mathematician John Coward in 1970... Basically he wanted to show that a system with really basic fundamental laws (Physics) could evolve and "live" to become a more complex system (Chemistry) in which "something" (humans) could work out its own model and complex rules to explain its reality… the rules for this deterministic model that he exposed were so basic that I thought it could be funny to implement them in ObjectScript when I had some spare time... there are others implementations in JavaScript and other languages... but not in ObjectScript... and that had to be corrected!!… so here you are!

Last comment 25 December 2018
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