An expert view on agile Data Warehousing
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...
The recent presentations provides a push to wrap up the development and release of the Data Vault virtualisation initiative, so now everything is working properly the next few posts should be relatively quick to produce. First off is the Satellite processing, which supports the typical elements we have seen earlier: Regular, composite, concatenated business keys with hashing Zero record provision Reuse of the objects for ETL purposes if required As this is another process going...
In the previous posts we have loaded a proper data delta (Staging Area) and archived this in the Persistent Staging Area (PSA). In my designs, the PSA is the foundation for any form of upstream virtualisation – both for the Integration Layer (Data Vault) and subsequently the Presentation Layer (Dimensional Model, or anything fit-for-purpose). The Presentation Layer sits ‘on top off’ the Data Vault the same as it would be in the physical implementation so you...
After setting up the initial data staging in the previous post we can load the detected data delta into the historical archive: the Persistent Staging Area (PSA). The PSA is the foundation of the Virtual Enterprise Data Warehouse because all upstream modelling and representation essentially reads from this ‘archive of (data) changes’. This is because the PSA has all the information that was ever presented to the Data Warehouse, either in structured or unstructured format....
Recent Comments