Or, should they be an integrated horizontal layer directly within the enterprise applications?

FORBES: More On The McKinsey Study: Integrating Into Workflows May Pay Off The Most

Integrating collaboration as a horizontal layer into the enterprise app incorporates new data types such as conversations, tags, comments and other collaboration content into the enterprise app itself.

FORBES: More On The McKinsey Study: Integrating Into Workflows May Pay Off The Most

In other words it a vertical add-on, or a horizontal core component layer?

FORBES: More On The McKinsey Study: Integrating Into Workflows May Pay Off The Most

DeClements uses vertical rebar with horizontal steel ties, plus a layer of waterproof insulation, electrical wiring and plumbing.

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Since the early 1990s the industry has resembled a cake made of horizontal layers of technology, with each layer dominated by a few companies.

ECONOMIST: Computing