Effective Dates in the Ed-Fi Data Model

This document provides information on the Ed-Fi Unifying Data Model's (UDM) approach to effective dates, and gives practical guidance on using the data model in contexts where effective dates are of particular importance.

Table of Contents

Overview 

The Ed-Fi data model is optimized to capture and transmit data that exists currently in source systems. This characteristic derives from the central Ed-Fi community use case of aggregating current operational data into a centralized location so that current, actionable insights and current reports (such as compliance or other reports) can be derived from that data.

As such, the Ed-Fi data model has limited support for the concept of "effective dates" — the dates where a transaction occurred or where organizational recognition of some data (often a demographic fact about an individual) was judged to be true. These latter entities are often seen in data models by using fields that employ an "as of" formulation, as in "the student was judged to be of race 'American Indian or Alaska Native' as of October 1, 2019."

The Ed-Fi data model therefore has no universal feature or strategy to capture effective or "as of" dates across all data entities, because many effective or "as of" dates do not exist in source systems.

This does not mean that the Ed-Fi data model does not have dates that can be used to determine effective dates: there are many such dates in the model. But those dates tend to be dates that are captured in their original source systems, because those dates have important value to local operational processes.

Examples

To clarify, let's consider some data facts that include dates:

1. On August 18, Paula Mills enrolled in the school Grand Bend Elementary.
2. On October 4, Paula Mills was determined to be eligible for Title I services.
3. On October 12, Paula Mills' name was changed to "Pauloa Mills."
4. On December 10, Pauloa Mills' race was changed from "Asian" to "American Indian or Alaska Native."

Of these facts that involve dates, the first 2 dates can be captured in the core Ed-Fi data model and the latter 2 cannot. The reasons why are simple:

• For facts #1 and #2, the date of an enrollment or program eligibility is a strongly governed process date, and so is universally present in student information systems (SIS). As such, those SIS systems can provide that date; as such those dates are included in the Ed-Fi data model.
• For facts #3 and #4, these are certainly legitimate "event" dates, but community experience has shown that student information systems either do not capture these dates or if they do, those dates are not easily surfaced in data exchange (e.g., the date is buried in an audit log and inaccessible via routine processes).

Underlying all of this is Ed-Fi's practical approach to data exchange. It is certainly possible to produce data models that capture all the possible "data event" or "validity" dates that an organization might be interested in (including dates for facts #3 and #4 above), but that model can't be populated by current operational data from actual systems. As a result, Ed-Fi data model does not include such dates. You can see in this Ed-Fi's focus on actualize-able data exchange rather than possible organizational data models.

The Period Entity

Ed-Fi does provide one optional pattern that can be employed to capture effective dates where they exist. 

The Period entity captures a BeginDate and an EndDate and can be used to provide dates that the value(s) of a data entity was judged to be valid. If you look at the use of this pattern in the Ed-Fi Address entity, you can see that it is used to (per the definition there) capture: "the time periods for which the address is valid."

It is important to note that all uses of the Period entity in the core Ed-Fi UDM are optional: it is this way because the community has evidence that some systems may capture this information (and be able to efficiently provide it) but some do not capture that information.

Guidance for Agencies

Given this, the Alliance provides the following recommendations.

When extending the data model to ask systems to exchange data (e.g., via an Ed-Fi API), limit requests for dates to those that are actually known to be present in source systems.

Asking for data that source systems do not possess results in localized and sometimes complex workaround for systems that communicate via Ed-Fi (e.g., "our SIS doesn't capture dates for a student name change, so I'll just put in the ADA student count date for the state") or forces the system to invent data (e.g., "our SIS doesn't capture the date that a student ethnicity was valid, so we'll just set the dates to the first and last date of the current term"). Neither is a desirable outcome for the systems or the community — the date is unreliable because it is not actually managed by the submitting system.

Instead of asking for effective dates on data entities, use current collection dates.

If an agency is interested in an account of how many students were classified as "Hispanic or Latino" on October 1, rather than collect "as of" dates on race, use the state of the collection data on October 1 to capture that data (e.g., by saving a copy of the submitted data at the end of the October 1, using change data capture, or a similar strategy).

The reason is identical to the reason behind the first recommendation: most SIS systems do not capture date changes for many data model entities, including race. To ask a system to supply historical values forces them to either create complex workarounds (at best) or to invent data they don't manage in a "best guess" manner (more likely).

Some agencies are surprised to learn that they can successfully dispense with many requests for "historical" data. Such asks are often a consequence of an agency's use of "collection windows" or similar strategies. But the experience of the Ed-Fi community has demonstrated that this is not only possible, but it is a far less complex (and likely expensive) process to build an ecosystem based on current operational data.

Guidance on how to enable and support such a "real-time" ecosystem is beyond the scope of this document, but readily available within the Ed-Fi community.

Limit use of the Period pattern by either making its use optional or be certain that all submitting systems in the data exchange context have the relevant date information.

The Period pattern is meant to enable optional collection of dates, recognizing that some systems may have dates while others do not. Agencies should resist making Period required, unless they are confident that all dependent, submitting systems have the data being requested.