Slides from my talk at MeasureCamp VII (London) in September 2015. Some key findings about Data Layers and how they are integrated with tag management solutions and organisations.

1. @SimoAhava

2. The Data Layer
MeasureCamp
@SimoAhava

3. Typically, there are three
definitions
of Data Layer that we use in
the digital world.
@SimoAhava from @ReaktorNow at #MeasureCamp

4. 1. Set of business
requirements
for tracking
digital assets,
visits, and
visitors.
2. Encoded, global
data structure,
accessed and
modified by
connected
platforms.
2. Data model of a
connected
platform, which
copies or digests
information in the
global structure.
dataLayer.push({
'pageType' : 'home'
});
google_tag_manager['GTM-123']
.dataLayer
.set('pageType', 'home');
@SimoAhava from @ReaktorNow at #MeasureCamp

5. Across all three definitions,
the purpose of a Data Layer
is simple:
@SimoAhava from @ReaktorNow at #MeasureCamp

6. @SimoAhava from @ReaktorNow at #MeasureCamp
DMP / DWH / TMS / etc.
X X
Actions Presentation
Data Layer

7. @SimoAhava from @ReaktorNow at #MeasureCamp
DMP / DWH / TMS / etc.
X X
Actions Presentation
Data Layer
The purpose of a Data Layer is to provide a bilateral layer on the digital
asset, which decouples, normalises, and uniformly encodes semantic
information passed through and stored within.

8. As a set of business
requirements, the Data
Layer is a living document.
@SimoAhava from @ReaktorNow at #MeasureCamp

9. - Can be encoded into a spreadsheet, a text document, or even simply as an interface design
of the front-end
- Important thing is to identify the variables in the Data Layer, with context and ownership
explicitly stated — each variable needs to have business impact / tie-in
- It’s a living document, so it should be kept up-to-date when changes to the dataLayer are
implemented
- Usually the document only reflects variables that are produced server-side (upon page
render)
@SimoAhava from @ReaktorNow at #MeasureCamp

10. As a global data structure,
the Data Layer is a
repository of information.
@SimoAhava from @ReaktorNow at #MeasureCamp

11. GTM’s dataLayer is an Array-type structure, which has a proprietary .push() method
@SimoAhava from @ReaktorNow at #MeasureCamp

12. Interaction is done most commonly by pushing an {object literal}, which has keys and values
of any JavaScript type.
@SimoAhava from @ReaktorNow at #MeasureCamp

13. The only method that works with GTM is push. No other Array methods have an impact.
@SimoAhava from @ReaktorNow at #MeasureCamp

14. As an internal data model,
the platform utilizes data in
the global dataLayer.
@SimoAhava from @ReaktorNow at #MeasureCamp

15. When you push a key into dataLayer, it gets copied into the internal data model.
@SimoAhava from @ReaktorNow at #MeasureCamp

16. When the value is an object, a recursive merge takes place.
@SimoAhava from @ReaktorNow at #MeasureCamp

17. The data model has some special methods as well.
@SimoAhava from @ReaktorNow at #MeasureCamp

18. Key learnings about how
the Data Layer should could
be used:
@SimoAhava from @ReaktorNow at #MeasureCamp

19. Pre-container-snippet-dataLayer is available to Tags firing with "All Pages" or "Page View"
Triggers.
@SimoAhava from @ReaktorNow at #MeasureCamp

20. Still, it’s a good idea to always have the 'event' key in the push, so that you can always use a
Custom Event Trigger as well.
@SimoAhava from @ReaktorNow at #MeasureCamp

21. Never use var dataLayer = []; as you can unwittingly destroy your GTM implementation.
@SimoAhava from @ReaktorNow at #MeasureCamp

22. eventCallback can be used to execute a function after the event has completed (i.e. all
dependent Tags have fired).
@SimoAhava from @ReaktorNow at #MeasureCamp

23. Values in the data model can be accessed with the Data Layer Variable.
@SimoAhava from @ReaktorNow at #MeasureCamp

24. Version 2:
- Dots can be used to access nested key names, and/or JavaScript properties:
—— someKey.nestedKey
—— someKey.parentElement.href
- Understands recursive merge, i.e. returns the full, merged object
Version 1:
- Dots have no function, i.e. they are interpreted as being part of the key name
- Does not understand recursive merge, so only returns the value that was most recently
pushed into this key
@SimoAhava from @ReaktorNow at #MeasureCamp

25. Square bracket notation does not work, replace with special dot notation to access Array
members (Version 2 only).
@SimoAhava from @ReaktorNow at #MeasureCamp

26. Values in the data model persist for the duration of the event. You can’t update values during
an event with dataLayer.push().
@SimoAhava from @ReaktorNow at #MeasureCamp

27. The Data Layer: http://goo.gl/9r4Ndw
Google Tag Manager’s Data Model: http://goo.gl/WhvSI9
@SimoAhava from @ReaktorNow at #MeasureCamp
FURTHER READING

28. @SimoAhava
@ReaktorNow
THANK YOU