Table 2. Data sharing issues and models.

	Shared Repository	Federation	Mediation	Grid	Linked Data	Common Model
Data ownership Data provider sensitivity to data distributed externally, and control of data.	-		-		-	+
Global scope Ability to integrate any relevant dataset into network.		-	+	+	+	+
Dynamic nature The network is dynamic, allowing for any relevant data provider to join, as opposed to a consortium of fixed members.	-	-	+			+
Data structure The data in the Alzheimer's disease domain is highly structured, and that must be preserved in sharing.	+	+	+	+		+
Harmonization Bring disparate datasets to a unified representation.	+	+	+	+	+	+