SharePoint 2013 introduces the concept of App level External Content Type(ECT) which allows model representing external entities to be packaged along with app in single unit so later it can be accessed by app to understand and integrate external data without outer dependencies.
External Content Types(ECTs) and External List – BCS(Business Connectivity Services) is an umbrella term in SharePoint referring to functionalities and activities for modeling, management and manipulation of external data. Schema of an external entity or business concept is represented in SharePoint by an external content type much like a content type describes native SharePoint entities. External List can then hold items of specific external content type, again the way List can have items of one or more content types. The major difference is External list can contain items of only one external content type.
What is inside BDC model?
Business Data Connectivity(BDC) model primarily contains information about,
- How to connect to external data source
- How to translate credentials if the user has a distinct identity in external system
- Metadata of one or more external entities
Farm Level vs App Level ECTs – In SharePoint 2010, model representing one or more ECTs, called BDC(Business Data Connectivity) model is stored in a relational database, called BDC Metadata Store. However this metadata store isn’t directly accessibly and managed by BDC service application. Adminsitrator or someone who has an access to Central Administration web site must upload the model and then it is available to any web application configured to use that instance of BDC service application. ECTs represented in such a way are called Farm Level ECTs.
Farm and App Level External Content Types in SharePoint 2013
Farm level ECTs works great for farm solutions and sandboxed solutions but not for apps in SharePoint 2013 as app is an isolated, compartmentalized unit and all data that app accesses including BDC model must be packaged along with it in a single unit so later it can be deployed to catalog or SharePoint Store without any external dependencies. App level ECT in SharePoint 2013 solves that problem. Here is how it does:
For Apps, model is stored in a file in a document library rather than in BDC metadata store. SharePoint then leverages less known feature FileBackedMetdataCataog, first introduced in SharePoint 2010, to read metadata from this file into in-memory BDC runtime which can be read by an external list. Like BDC server runtime, this BDC runtime can connect to variety of data sources through out-of-box connectors such as SQl Connector, Web services connector and OData connector. Custom connectors and .net assembly connectors cannot be used along with this runtime and hence with App level ECTs. This may sound limiting but actually it is consistent with overall App idea which doesn’t allow any custom code to run on SharePoint server.
App Level ECTs
- Allows granular isolation of external content types for an App
- An app can have only one BDCM file and that is referenced in ListInstance definition by MetdataCatlogFileName property.
- Doesn’t need an access to BDC service application
App level ECTs empower a SharePoint App to access and manipulate publicly available data sources without any configuration on the consumer’s part. App can work with external data right after it is installed.
