Managing the Resources of a Project

See Project Design Discussion for background information.

Knowing which resources of a project to load into memory and when.

Assume that a project requires a set of resources {R1, R2, R3}. In the new design, this can be modeled using the internal attribute resource owned by the Project. This alleviates the project from having a separate data store for holding onto the resources). When the project is loaded into memory, R1 and R2 should be loaded as well but R3 should not (perhaps R1 is the model, R2 is the analysis mesh that the user wishes to use, and R3 is a courser mesh that the user might use in the future). How do we capture this and what mechanism is to be used to perform the action?

1. Project does all the work

This approach requires each derived project to provide an operation to explicitly load the resources into memory. In this example, the designer would create a LoadOperation that would load in R1 and R2 (if they’re set) when the project loads.

2. Base Project provides an initial structure.

In this case, the base project class could provide a simple structure to its internal attribute resource. For example it could have an Attribute Definition called “LoadImmediately” and one called “LoadLater”. A derived project could then add a set of ResourceItems to either of these Definitions and the base project load operation would load all resources listed in the former but not those in the latter. In the above example, R1 and R2 would be captured by ResourceItems under the “LoadImmediately” Attribute and R3 would be a ResourceItem under the “LoadLater” Attribute.

3. Extend Resource Item and its Definition

This approach delegates this responsibility to the ResourceItem and ResourceItemDefinition classes. The ResourceItemDefinition class could have a new property called LoadRequirements with values {LoadImmediately, LoadOnDemand}. An operation could then be created that would walk the attribute resource and load those resources marked with LoadImmediately. In addition, the ResourceItem would also have a boolean property called LoadImmediately that returns true its definition has LoadRequirements = LoadImmediately or if it is marked to be loaded explicitly. The idea for this is to capture the case where the user has loaded the resource into memory explicitly and wants the workflow to remember to load the resource the next time the project in loaded into memory.

In the case of the above example, the ReferenceItemDefinitions for R1 and R2 would have LoadRequirements = LoadImmediately and R3 would have its set to LoadOnDemand.


Approach 1

Simplest to implement.

Approach 2

  • Very simple structure that makes it very easy to define new types of projects.
  • Base Project can provide a load operation that derived projects could reuse.

Approach 3 (My Current Choice)

  • Most flexible and can be used outside of the Project Concept
  • Generic Resource Load operation could be created and used both by project and non-project workflows
  • Base Project does not enforce any information structure in terms of capturing a project’s resource requirements


  • Approach 1 - Every project will need to implement its own “load” operation
  • Approach 2- Initial structure can appear limiting
  • Approach 3 - None that I see

Relating Project Resources with Task Resources

Let’s assume we have a project that has a set of resources, how can a Task in the Project’s workflow refer to these resources? Once again there are several options:

  1. The Task uses a ResourceItem that is manually set to the correct resource (either by hand or through an operation). In this case it’s up to the project logic to get this right.
  2. Use Properties or LinkRoles - in this approach, the Task ResourceItem would be constrained to hold only specific resources which could be tested when determining if the user is allowed to enter that Task. Note that the operation to change the Property/Link Association would not be contained in the Task itself. Meaning that the user would need to leave the Task and enter the one that provides the operation. Note that this would allow the Project to represent a resource as LoadOnDemand while the Task could have it marked as LoadImmediately.
  3. Use something like an ItemVariant to directly refer to the item in the Project

Projects and the Resource Manager

Lastly I wanted to bring up the issue of how Projects and their Resources work with respects to the Resource Manager. Lets assume we have the following:

  1. Project 1 (P1) requires resource (R1)
  2. Project 2 (P2) requires Resources (R1 and R2)
  3. The user loads in P2 which means R1 and R2 should be accessible in the Resource Manager.
  4. The user then loads in P1 which doesn’t require anything to be loaded since R1 is already loaded via P2.
  5. Now the user unloads P2. R2 should be unloaded as well though R1 is still needed.
  6. Finally the user unloads P1 which should also result in R1 from being unloaded.

Currently the Resource Manager holds a shared pointer to the resource when it is loaded which means without any modification to the code, resources loaded in via Projects would not get removed when the Project is removed.

Here are a couple options:

Project Resources are held by the Project and not the Resource Manager

This would solve the above problem but at the cost of introducing a bigger problem. Namely Projects would need to provide the same search functionality the Resource Manager provides.

Resource Manager has the ability to hold a Resource using either shared or weak pointers

If there was a way to indicate that a resource should be added to the Resource Manager using either shared or weak pointers then the above example would work as described assuming that P1 and P2 Resources indicated the Resource Manager to hold them using weak pointers.

This would also address the following modification of the above example:
4a. The user directly loads in R1

In Step 4a, R1 would be found to be in the ResourceManager as a weak pointer. Since the resource load operation would then add it to ResourceManager as a shared pointer as well.

Since the ResourceManager uses a multi-index array, the simplest way of possibly supporting this would be to have the ResourceManager maintain two arrays - one using shared pointers and one using weak pointers. The same resource could exist in both depending on the circumstances.

Its the Project Manager Job

This is sort of the dual of the above approach. The Project Manager could keep track of all Projects in the system (which would be its main job). When a Project is being unloaded, the Project Manager would grab the Project’s list of loaded resources and remove those Resources that don’t exist in either another Project or has been directly added to the Resource Manager.

I agree with your conclusion. It seems to me that extending Resource Item and its definition provides the most flexibility, and therefore offers the most potential for SMTK managing resources throughout the lifespan of a project.

Regarding item #1, I agree that adding this capability to ResourceItem is the way to go. Before moving on, I think we should also clarify, and possibly extend, what the term “load on demand” means. For example, when editing a project’s attribute resource, I presume we will be able to set a ResourceItem value to some project resource whether that resource is in memory or not. Similarly, the ResourceItem.value() should be able to return some kind of info/placeholder/descriptor for a resource not currently in memory. In other words, the process of loading an on-demand resource should always be initiated by the application, not SMTK.

Regarding item #2, I don’t have an opinion on the implementation, at least not yet. The one recommendation I have is to reframe the issue. The current wording considers how workflows can refer to project resources. In contrast, I think the reverse perspective is more applicable. In other words, each workflow should define the resources it uses with whatever mechanism TBD, and it will be the project’s job to provide storage and management of them. So I see 2 main parts to this issue:

  • How do workflows specify and represent their resources (and data assets in general)
  • What API does the project provide for workflows to access those resources/assets

Also, because this is a new project/workflow discussion, I am contractually obligated to reiterate my usual comment that we need to extend projects to support simulation assets that are not SMTK resources. This is a requisite feature.

Well said, and an important distinction I think.

Sorry to make you repeat yourself, but could you provide a brief example for clarity?

By SMTK resources I mean smtk::resource::Resource and its subclasses. This comprises the various model types that SMTK supports along with our mesh and attribute resource types. I presume that our first implementation will be limited to these data types, but there are other data generated and used during a simulation workflow/lifecycle that we will also need to support, most notably simulation input decks and output results. (There is also at least one more data type that I remember from a nuclear application.) So my comment is mostly to remind our guys that we need to generalize our notion of “resource” to include other data types that are not based on SMTK.

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Thank you! I was hoping to hear this. As you pointed out, supporting these assets brings continuity to the simulation workflow/lifecycle (and Project).

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