An expert view on agile Data Warehousing
Over the weekend I have written up a brief overview and ‘thought piece’ of what I mean when I talk about a Virtual Data Warehouse and Data Warehouse Virtualisation. Please have a look at the article here: The Virtual Data Warehouse. A special thanks to Bret Victor for sharing a fascinating presentation on ‘inventing in principle’. This is a concept, or I should rather say a principle, I have been working on for some time now....
What value do we get from having an intermediate hyper-normalised layer? Let me start by stating that a Data Warehouse is a necessary evil at the best of times. In the ideal world, there would be no need for it, as optimal governance and near real-time multidirectional data harmonisation would have created an environment where it is easy to retrieve information without any ambiguity across systems (including its history of changes). Ideally, we would not...
I receive a fair bit of questions on the Data Warehouse Virtualisation ideas and wanted to respond and discuss this via this post. I don’t have all the answer but can share my views and expectations. When it comes to DWH Virtualisation and the Persistent Staging Area (PSA), the questions generally fall into two categories: Isn’t it too slow? How about performance? Surely users don’t want to wait for hours to see results? Why bother...
After a bit of a pause in working on the weblog and technology (caused by an extended period of high pressure in the day job) I am once again working on some changes in the various concepts I’m writing about on this site. Recently I was made aware of this great little tool that supports easy creation and sharing of simple data models: Quick Database Diagrams (‘QuickDBD’). The tool is 100% online and can be...
I’ve completed a fairly large body of work that I’ve been meaning to do for a long time: how to automatically version the Data Warehouse data model in sync with the version of the ETL automation metadata. Although versioning models and code is relevant (but rarely implemented) in the traditional ETL area, this requirement to becomes very real when moving to a virtualised Data Warehouse / integrated model approach (Data Vault 2.0 in my case)....
Recent discussions around Data Warehouse virtualisation made me realise I forgot to post one of the important requirements: version control. In the various recent presentations this was discussed at length but somehow it didn’t make it to the transcript. Data Warehouse virtualisation needs versioning. Think of it this way – if you can drop and refactor your Data Warehouse based on (the changes in your) metadata then your upstream reports and analytics are very likely...
This is the second part of the Link Satellite virtualisation overview (the first post on this topic is here), and it dives deeper into the logic behind Driving Key based Link Satellites. Driving Key implementation is arguably one of the more complex things to implement in Data Vault – and you (still) need to ensure you can cover reloads (deterministic outputs!), zero records / time variance and things such as re-opening closed relationships. In the example...
The final of the series of planned posts (for now at least) about Data Warehouse Virtualisation is all about Link Satellites. As with some of the earlier posts there are various similarities to the earlier approaches – most notably the Satellite virtualisation and processing. Concepts such as zero records and ‘virtual’ or computed end-dating are all there again, as are the constructions of using subqueries to do attribute mapping and outer queries to calculate hash...
One of the last items to write about regarding Data Warehouse virtualisation (and any other form of ETL generation) is the handling of the metadata itself. In a previous post I covered what metadata needs to be captured at a minimum for ETL automation, and this post is all about how to incorporate this metadata from various locations. One technique in particular I tend to use is the user defined properties (or extended properties) of...
Virtualising Data Vault Link structures follows a similar process to that of the virtual Hubs, with some small additions such as the support for (optional) degenerate attributes. To make things a bit more interesting I created some metadata that requires different Business Key ‘types’ so this can be shown and tested in the virtualisation program. For the example in this post I created three Link definitions (the metadata), one of which (LNK_CUSTOMER_COSTING) has a three-way relationship with the following...
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