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Notifications and Filters

When a Collection is small, it may offer you search features and random access to separate Units. For larger Collections —and when you wish to have some caching— you should use Collection feeds: the client automatically gets copies of Units in regular intervals, to catch-up with the Collection source. Only Units which match a certain pattern are transported: via a pre-configured Filter.

Besides passively retaining filtered Units, you can also enlist as client to notification: when anything changes in Units which you are monitoring, you will receive a Notification. Most importantly: when there are life-cycle state changes. You may receive notifications for Units which you have not seen.

Sub-setting a Collection

Clients have an incomplete view on the status of the main Collection: they can ask the Meshy Space layer to download a subset of Units onto a local storage. This downloading might be delayed, especially when the source Collection is really large.

The client always register for the change notification feed provided by the Collection. This feed contains life-cycle state changes for the (sub-set of) Units which you have selected. This feed MUST be processed at least daily: it is a requirement of every data License, which you are required to sign before access to a namespace is granted. The feed may contain Units which are Withdrawn and Expired, which SHALL be processed immediately.

The Collection MAY also provide your local extract with all Units which have been updated and match your filter rules. This transport is really efficient, but also slightly delayed.

Producing feeds might be resource expensive for the Collection server, so it may restrict your options and may also produce feeds which contain much more than you ask for. The feed may also be broken-up into multiple (large) fragments. The Collection determines the distribution process.


On the client-side, any connected Collection has a local Cache Collection, which minimally contains Namespace and Rules. Information which arrives via Feeds is stored in the Cache Collection.

The Cache will keep a "received" time for each Unit and an "auto-clean" timeout. Also, the client application may forcefully remove Units from the local Cache; the Cache works as Unit buffer. The source Collection MAY not support the reload of Units outside a feed.

mark@overmeer.net      Web-pages generated on 2023-12-19