I can hardly believe it's been eight months since I last wrote about the NISO I2 project. A lot has changed since then[1]. I continue to work on I2 however; they won't get rid of me that easily.

In the last post, I wrote:

The next step is to build upon the report to draw yet more conclusions from the data — there's an awful lot there — and flesh out some repository use cases for institutional identifiers. The I2 core group is moving quickly towards finalizing identifier metadata elements so that a standard may be drafted, and I think having some use cases documented will help drive the standard in a direction the community can get behind.

Since that time, the three scenario groups — Electronic Resources; Institutional Repositories and Learning Management Systems; and Library Resource Management — have concluded their work. The work of the scenario groups included surveys of over 300 people working in these fields. The survey results have been analyzed and reports were posted on the NISO website. These reports have been used to flesh out use cases for an institutional identifier. Upon completion of this work, the scenario groups were disbanded and work continued in a broader I2 working group.

The I2 working group has concentrated its work on analysis of similar standards and, as I alluded to earlier, significant effort has gone into defining core metadata to identify institutions, such as institution name, institution type, location information, variant identifiers, domain name(s), URL(s), and (optionally-typed) relationships to other institutions. During these discussions it was difficult for me to hear the issues and needs around I2's metadata and identifiers without linked data springing to mind.

While we are designing a standard and not a system or a service per se, it seems useful to include in the standard an informative section about implementation and architecture[2]; I find that reading standards is much easier on the brain when you get not only the standard itself but some examples of implementation, and that will be true as well, one hopes, of I2 standard implementers. To that end, the group will be producing an XML schema of the I2 metadata elements and also an RDF schema.

I have been working on the RDF for I2 on and off for the past month or two. Below are my impressions, as someone who is new to modeling in RDF, and the procedures I used to produce the draft RDF schema.

Despite their names, RDF schema and XML schema are quite different[3]. The XML schema is a tool for validating an XML-based document or record, and it's a common tool for modeling metadata in libraryland. Not so with RDF schema, where the notion of document or record is replaced by the notion of a set of triples. The focus in RDF is on the triple not on the document, and so validation of documents or records is not the point of RDF schema. This took some effort to wrap my mind around.

Before I modeled I2 in RDF, I sketched out a domain model of I2 by copying relevant bits of information from I2 documents and pasting them into a text editor. Then I put them into classes. In I2's case, the domain model contained three classes of things: metadata elements about an institution, relationships between institutions, and types of institution.

I gathered some examples of relatively simple RDF schemas and transformed them into the Turtle serialization format[4] for ease of reading, using them as a template for the I2 schema.

In the RDF schema (RDFS) specification, there are two classes of things in the domain model: classes and properties. If you are familiar with object-oriented programming, chances are you already grok this way of modeling, but otherwise, generally: a class is like a type and a property is an attribute. If I were to model myself in RDF schema, then, I might say I am in the class of human beings, and one of my many properties is having a particular birth date, and another is having been born in a particular city. The next step was to take the I2 domain model (metadata elements about an institution, relationships between institutions, and types of institution) and decide whether each thing was a class or a property. I decided that the former two were sets of properties and that type of institution could be modeled as a set of classes.

Having a conceptual model of I2 and how it fit into the RDF schema way of thinking about things, I wrote a simple ontology defining one RDFS class per type of institution, and one RDFS property per metadata element and one per relationship type. This would have sufficed as an ontology.

Exposing RDF-based resources on the web as linked data, however, represents an opportunity for metadata element-level interoperability at global scale. In order to interoperate with the existing corpus of linked data available on the web, I went through the new I2 ontology and looked for areas where I could re-use, or subclass or otherwise link to, classes and properties already defined in more widely-used ontologies. I realized at this point just how different coming up with a new XML document format was from writing an RDF ontology; whereas I might have wanted the former to be comprehensive and inclusive of every single aspect within the I2 domain model, my goal with the latter became to eliminate it (by trimming it down to only those bits which are not defined elsewhere).

Since the RDF ontology for I2 is not inclusive of the entire domain model, it seemed necessary to produce another reference document: a set of instances of I2 resources showing the mingling of new I2-specific classes and properties with well-defined classes and properties from other ontologies.

I shared rough first drafts of these documents and received very helpful feedback from some folks who are better-versed in this than myself. I've now incorporated their feedback into the latest I2 ontology and instance document. I hope to include both of these into a draft of the I2 specification which will go out for comment in the coming months. Here's the latest ontology and the latest set of instances.

Notes

1. I've moved and changed jobs, in fact
2. This practice seems more or less common in my (admittedly limited) experience, cf. the unAPI specification.
3. This reflection should come as little surprise since RDF and XML are different kinds of things: RDF is a data model and XML is a serialization format.
4. Using rapper, a nifty little tool.

As far as I'm concerned, the most exciting developments this year in repositories and digital curation have come out of the California Digital Library. It has been impossible not to notice their papers and presentations. Put simply, their idea is that digital curation is enabled by "micro-services" built upon well-known abstractions such as the filesystem. The benefits are obvious: filesystem tools are ubiquitous and cross-platform, and there are strong market forces to ensure the filesystem persists. The idea is radically simple and straightforward, though many questions remain about such a paradigm. I'll return to those later.

If you have not yet taken a look at CDL's curation micro-service specifications, most of which may be printed on as few as one or two sheets of paper, see the Digital Library Building Blocks.

My co-workers in the LC Repository Development Center have been chatting about these specs on and off throughout the year. After months of procrastinating, I finally read all of the specs on Thursday; it's wonderful that you can do so in the course of one reading session, I might add. Yesterday a bunch of us RDCers got together to chat (informally) about the specs: what they're for, how they work, and how they interact with one another. I learn by doing, by examples, so I combed through each of the specs in advance of our meeting and tried to construct a minimal repository[1] based on micro-services.

Here is a tree visualization of the final product, inevitable warts and all: The services I used were Namaste, Content Access Node (CAN), Pairtree, Dflat, Reverse Directory Deltas (ReDD), Class-based System for Managing Object Properties (CLOP), and BagIt (co-developed by LC and CDL).

As I mentioned in our Friday meeting, recounting my experience exploring the specs: the bad thing is that I spent an hour building a repository with rudimentary tools such as mkdir, touch, cp, ln, and emacs; but the good thing is that I built a repository in one hour using common, rudimentary tools. It's a very compelling paradigm. Ed's already built a tool implementing some of Dflat, further demonstrating how lightweight these micro-services are. (UPDATE: Ed notes that this code is a work in progress and is "barely functional.") (UPDATE 2: The dflat library has come a long way. Check it out if you're interested. Also, I just committed a pretty basic Namaste library: http://github.com/mjgiarlo/namaste. Only took about an hour, which is a testament to the power of lightweight specs.)

I am certain this will be a running thread at work as the specifications evolve and our understanding of them grows. Some questions and comments that occurred to me while exploring the micro-service specs and building the minimal repo:

• CAN was a bit puzzling. The spec is simple enough, but I found some of the conventions confusing, and I was left wondering what CAN provides other than a container. What I would like to see is a simple use case and perhaps more examples. Thus, the CAN stuff in my sample repo doesn't feel very useful only because I had a hard time working with the spec.
• CLOP feels like the least mature of the specifications. It seems generally useful to be able to put digital objects, however you define that, into classes and define properties on those classes. The spec did not clearly convey to me just how it accomplishes that aim. A few examples would go a very long way. I've got some CLOP stuff in the sample repo but I have no idea how close my implementation matches the spec.
• Is Dflat dependent on ReDD? One would assume not since there's an optional property in the dflat-info.txt file for specifying a delta scheme. But, say, could you stub out the v001 directory (reserved to hold the initial version of a digital object) and use a system such as git or bazaar?
  
  One might argue that these established delta schemes, if you want to call them that, have many more developers and users than a system such as ReDD and thus should persist longer and have more tools built around them. I imagine the micro-service viewpoint would acknowledge that point, but counter that the spirit of these specs is to avoid dependencies from outside the filesystem?
• Is the ReDD specification meaningful outside of a Dflat given that any one ReDD directory knows nothing of its successors and predecessors, or is it dependent upon Dflat?
• Could a BagIt bag live inside of the ReDD reserved "full" directory? That is, could the "full" directory be marked up appropriately to be a BagIt bag?
• How many tools exist for these specs? I notice there's code in CPAN for Pairtree and Namaste, which is a fabulous start. Tools are the difference between YAMF (Yet Another Messy Filesystem) and reliably managed curation services. Granted, tools such as cp and emacs already exist and are part of the appeal of these micro-services, but there's also tremendous room for error if operations are all done "by hand."
• To what extent has CDL transitioned to using these specs/tools?
• Are other institutions using these specs/tools? I have heard tell that digital library folks from the University of Michigan and the University of North Texas may be involved.

I hope I don't sound overly critical. I'm really glad our colleagues at the California Digital Library have written these specifications and applied their deep experience to what could be a transformative paradigm[2] in the digital curation world. Kudos to them!

Notes

1. Perhaps it's more in line with the specs to refer to this space as "a managed filesystem that drives repository and curation services," given the CDL philosophy that preservation is not a place/repository. But it's easier to say "repository," so there you go.
2. Please excuse the fanboyishness; this filesystem fetishism is exciting stuff!

I wrote in June that the I2 subgroup surveyed "repository managers to determine the current practices and needs of the repository community regarding institutional identifiers. Results from the survey will inform a set of use cases that will be shared with the community, and that are expected to drive the development of a new standard for institutional identifiers."

The survey closed in July, and the subgroup spent August writing a report on the survey results. That report is now final and it's available to the public. Feedback may be sent to our (woefully underutilized) public i2info mailing list, left as a comment on this post, or e-mailed to me privately which I can forward to our internal list.

The next step is to build upon the report to draw yet more conclusions from the data — there's an awful lot there — and flesh out some repository use cases for institutional identifiers. The I2 core group is moving quickly towards finalizing identifier metadata elements so that a standard may be drafted, and I think having some use cases documented will help drive the standard in a direction the community can get behind.

Onward and upward.

[Series]

Near the end of my strawman post, I wrote:

The I2 repositories subgroup will be sending out its survey on identifier use cases in the coming week. It will be interesting to see if the requirements we have thus far identified still obtain in light of the data we collect from the survey.

We completed the survey late last week and began distributing it. Here's what we sent out:

The NISO I2 Working Group is surveying repository managers to determine the current practices and needs of the repository community regarding institutional identifiers. We value your time and your input in the process to create a standard for a new institutional identifier. We hope that you will complete the survey which should take less than 15 minutes. The survey will remain open through Monday, July 6th.

Here is a link to the survey:
http://www.surveymonkey.com/s.aspx?sm=RGQgZ3090DVrb3kFzr3P3Q_3d_3d

Please feel free to share this message with other interested parties.

First we used Survey Monkey to send the survey link to approximately one-hundred repository managers that the subgroup identified. Our process for identifying repository managers involved pulling together a list of prominent repositories from subgroup members, and then gathering more from OpenDOAR, "an authoritative directory of academic open access repositories." Then subgroup members were encouraged to share the survey link with colleagues, and post it far and wide via blogs, listservs, and tweets. The listservs we targeted were: JISC-REPOSITORIES, metadataLibrarians, digital-curation, SPARC-IR, ir-net, REPOMAN-L, PALINET-IR-L, dspace-general, fedora-commons-users, DC-IDENTIFIERS, and code4lib.

I've already received a few responses and have gotten useful feedback. Two of the hardest questions to answer so far have been: "What is an institutional identifier?" and "What is a repository?"

Institutional identifier

An institutional identifier is defined as a symbol or code that uniquely identifies an institution. Domain-specific examples of existing identifiers include SAN, IPEDS, GLN, MARC Org Code, and ISIL. Another example might be a Handle prefix or ARK name authority assigning number.

Repository

Institutional repositories and subject repositories like arxiv.org are clearly 'repositories', but beyond that it is a somewhat ill-defined term. One might look to the Kahn-Wilensky architecture, or the OAIS reference model (PDF), or even Wikipedia for definitions, but it's not clear that even the authorities agree on what constitutes a repository.

It's a system. It's network-accessible and typically has a web interface of some sort. Files and groups of files sometimes known as objects tend to be deposited in them, perhaps for some combination of management, access, or preservation. Many run Fedora, DSpace, and ePrints, and factor heavily in scholarly communication. Some are document-centric. Some will accept anything. To some, a learning management system may be a repo. To others, a content management system may fit.

My background is in academia so my own definition is somewhat based in that context, but I wouldn't say the term is necessarily limited to that context. There are other NISO I2 scenarios for library workflows and electronic resources, so it's safe to assume that repository does not mean ILS or OPAC or ERP system. My hope is that folks have their own working definitions of the term and can decide for themselves what it means.

We've given folks a little over two weeks to respond to the survey, so the constant I2 drum-beating will quiet down for a while around here. I am very interested in what sorts of responses we get from the survey. Fun times!

Oh, and perhaps it goes without saying, but if you're a repository owner, manager, expert, developer, or stakeholder with an interest in identifiers, please feel free to take the survey!

[Series]

In the prior I2 post, I wrote about the requirements the repositories subgroup has come up with for an institutional identifier standard (with the hope that our findings re: repositories could be generalized to other scenarios).

My strawman proposal of sorts is to explore how well linked data patterns fit this problem space. Linked data, briefly, is a way to expose and link data on the web in a more semantically meaningful way, and is often summarized using the four principles put forward by Tim Berners-Lee:

1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful information.
4. Include links to other URIs. so that they can discover more things.

That's the crux of it.  Linked data takes well-known patterns on the web (linking, dereferencing, etc.) and applies them to data, which in this case could be metadata for identifying institutions.

Let's examine each of the requirements and the applicability of linked data thereto.

1. Should be agnostic to type of institution, e.g., libraries, museums, personal collections, historical societies: The web is already agnostic to type of institution.  HTTP URIs do not favor one type of institution over another.
   
2. Should handle varying institutional granularity, e.g., institution-level, campus-level, division-level, unit-level: HTTP URIs are flexible in this regard.  Hierarchy, should one wish it to be surfaced in the identifier, may be encoded in either a DNS hostname or the path appended to the DNS name.  One can imagine a URI like "http://department.division.institution.tld/unit/subunit" or "http://institution.tld/campus/office/individual".
   
   Hierarchy needn't be surfaced in the identifier if one favors opacity, in which case "http://registry.tld/xnjsdasd" would suffice as an identifier, and may instead be entirely reflected in the (RDF) representation returned by dereferencing the URI.
   
3. Should handle linking among institutions and subordinate units: Linked data handles linking via well-known HTTP mechanisms, referenced in the fourth principle of linked data.  Unlike the HTTP link, which has limited semantics, linked data links are semantically rich and extensible.
   
4. Should express different sorts of relationships among these institutions and units: The "useful information" in the third principle of linked data is typically provided by an RDF representation, which is itself a list of assertions.  These assertions, or triples, consist of subjects, predicates, and objects.  The ability to express the relationships in this requirement is limited only by the availability of vocabularies that contain sets of predicates and classes for subjects and objects.  Think of the predicates as elements defined within a metadata standard, e.g., Dublin Core "creator", MODS "relatedItem", and so forth.  Vocabularies that contain these predicates and classes are growing and evolving daily, and should there not be a vocabulary that contains the relationship one wishes to express, it is fairly easy to create a custom vocabulary.
   
   The ability to mix and match vocabularies provides an expressiveness that is often not found in document-based metadata formats and the flexibility to express radically different relationships on a per-industry or per-institution basis.  This latter point is important as the I2 group has identified both core metadata elements for identifying institutions of different types and additional elements for specific types of institutions.  Why re-invent a new metadata format or schema when all one needs to express may already be contained in others?
   
5. Should relate to existing relevant identifiers and registries: Same as requirement#4.  Linked data is all about expressing relationships between things, e.g., institutions, identifiers, registries, etc.
   
6. Should be globally unique: HTTP URIs are guaranteed to be globally unique by virtue of the distributed DNS system and hierarchical naming within each HTTP service.
   
7. Should be actionable: HTTP URIs provide dereferenceability/actionability via the well-known HTTP protocol.
   
8. Should enable retrieval of metadata sufficient to identify the institution, which may vary widely by institution: HTTP URIs are actionable per requirement #7 and the metadata returned is flexible per requirement #4.
   
9. Should accommodate changes as institutions come and go and re-organize and be able to relate defunct institutions to new ones: Linked data patterns provide for redirecting from defunct representations (institutional identifiers) to new ones via HTTP redirects.  One may also add assertions to institutional metadata such as owl:sameAs, for instance, which says that the institution identified by the given URI is the same as another institution identified by another URI.
   

This seems like a compelling path to follow for the I2 standard.

The I2 repositories subgroup will be sending out its survey on identifier use cases in the coming week.  It will be interesting to see if the requirements we have thus far identified still obtain in light of the data we collect from the survey.  If so, I would like to explore the idea of linked data for institutional identifiers a bit more.

[Series]

The I2 IR scenario subgroup approached the issue of institutional identifiers in repositories by first brainstorming about the various issues, problems, and sticking points that make identifiers in this space (and elsewhere) such a complex topic. Folks on the subgroup are repository managers or are otherwise involved with or knowledgeable about the repository space, so the brainstorming exercise yielded a good number of concerns.

The purpose of the exercise was to enumerate concerns and issues that could inform a draft survey to be administered to repository managers and experts around the globe in different organizational contexts: libraries, subject disciplines, archives, historical societies, etc. The purpose of the survey is to get an idea of the use cases and constraints around institutional identifiers in these different repository contexts, the assumption being that we ought to have requirements grounded in real world usage before we go off building a standard.

I will note here that the subgroup has worked up a draft survey that has just recently been reviewed by a small group of folks who know about survey design, and we hope to administer the survey to the aforementioned Reporati this week[1]. Which is to say that I don't yet have a strong grasp of the use cases out there in the wild, and this series should be construed as my own premature cognitive fumblings. But let's assume for now that what we learn from the survey results matches our initial brainstorming exercise.

Here is a slightly modified and boiled down version of the concerns and issues the subgroup came up with for a potential institutional identifier standard, which resembles a set of minimum requirements:

1. Should be agnostic to type of institution, e.g., libraries, museums, personal collections, historical societies
2. Should handle varying institutional granularity, e.g., institution-level, campus-level, division-level, unit-level
3. Should handle linking among institutions and subordinate units
4. Should express different sorts of relationships among these institutions and units
5. Should relate to existing relevant identifiers and registries
6. Should be globally unique
7. Should be actionable
8. Should enable retrieval of metadata sufficient to identify the institution, which may vary widely by institution
9. Should accommodate changes as institutions come and go and re-organize and be able to relate defunct institutions to new ones

I doubt the list is exhaustive; I am almost certain we will uncover all sorts of tangly and esoteric use cases that add requirements. I expect it. Why else would we be gathering to discuss the need for an institutional identifier if it were a solved problem or a simple one? [2]

Nevertheless, looking at the above list, the task we've taken on starts to feel less onerous. And thinking about identifier systems constrained by the list of concerns, the mind starts to cook up all sorts of possible solutions. I'll share one in the next post in this series, a strawman proposal of sorts, and how it addresses each of these requirements.

Notes

1. We will also x-post to repo-related mailing lists as well, and some of us may blog or tweet about it. My inclination is to cast as wide a net as possible so as not to miss important use cases. We can always scope things out later on, but it's useful to be inclusive at this point lest our own assumptions carry the group forward.
2. The cynical among you might have interesting answers to this question.

[Series]

This is the first in a series of posts about institutional identifiers[1].

In my last post, I alluded to some documentation that I've written. That was somewhat misleading, which will soon be apparent, but I liked the parallel construction I had going, and I am but a slave to orderliness.

For about the past six months, I have been working with a NISO group looking into how institutions are identified within information systems:

The I2 (Institutional Identifiers — pronounced "I 2") working group will build on work from the Journal Supply Chain Efficiency Improvement Pilot (http://www.journalsupplychain.com/), which demonstrated the improved efficiencies of using an institutional identifier in the journal supply chain. The NISO working group will develop a standard for an institutional identifier that can be implemented in all library and publishing environments. The standard will include definition of the metadata required to be collected with the identifier and what uses can be made of that metadata. …

The I2 group is split into a few subgroups which have been charged with looking into how institutional identifiers are used in particular scenarios. These scenarios are e-resources, repositories and e-learning systems, and library resource workflows. The scenario names pain me a bit, but so be it; this is our industry, and there are bigger windmills to tilt at.

I am currently co-chairing the subgroup looking at repositories and e-learning, and apparently I am its "tech lead." I don't want to get caught up on names and roles and titles, though; this series isn't about those at all. I'm just setting the scene and explaining why my head's in this space and laying bare my stake in the issue.

The remainder of this series will provide a bit more detail on the issues around institutional identifiers, share how the repository subgroup is grappling with identifier issues and engaging the repository community to assess needs, propose an approach for an identifier system that may meet said needs, and explore what seems to be the thorniest issue[2].

Notes

1. I offer that very tentatively, knowing what a spectacular failure my last attempt at a series was.
2. Hint: management. I know, "duh," right?

While doing some reading for a little talk my colleague, Ed Summers, and I are giving at code4lib 2009, I came across a paragraph that sparked a crazy thought. So crazy that it's not crazy at all. So not crazy that I am sure other people have thought of it. But nonetheless, here I am writing about it just in case.

From Sarah Currier's paper on SWORD (emphasis mine):

One of the most frequently cited barriers to academics depositing their teaching materials into repositories is the keystroke-count involved in logging into a repository, uploading the resource, creating metadata, perhaps selecting a licence, and publishing the resource. It was a quick win, therefore, to create a drag-and-drop desktop tool to allow a single keystroke deposit of resources, including multiple resources in one action. For a repository that supports automatic metadata generation, administrative metadata can be created at the point of entry to the repository without the user needing to create any.

And I wondered how many repositories supported automatic metadata generation. I wondered how many repositories supported automatic generation of rich metadata. And lastly I wondered, might this be a more or less natural role for catalogers: augmenting stub metadata records or doing original cataloging for institutional repository deposits? Especially at a time when many of them are being reclassified as acquisitions specialists or digital projects managers?

Potential issues and questions:

• Author ignorance: Maybe catalogers are already doing this and I'm a moron?
• Scale: Is it realistic to expect to be able to "keep up" with repository deposits?
• Granularity: Does cataloging at the level of articles, and perhaps at even finer granularities, introduce challenges?
• Duplication: If pre-prints are cataloged in the IR, for instance, will they need to be cataloged again later?
• … there are others I thought of on my commute this morning but have since forgotten them. Feel free to add comments.

I will admit here that I've been somewhat out of the (academic) institutional repository space a while, and cataloging is something I don't share thoughts about very often because my exposure is limited to having taken one course a couple years ago.

I assume there's a body of research about this out there somewhere but I figured I'd post this anyway.

Lest I be criticized for unfairly calling out former employers in my recent Burn the Walled Gardens rant, I share news that the Rutgers University Libraries have boldly ventured into the world of open source software: RUcore Open Source Development. Huzzah! Thanks to the molotov-hurling Shaun Ellis, a peacenik/code monkey/musician extraordinaire, for all of his work and for bringing this to my attention.

On the RUcore open source page you can get a list of ongoing projects, a release schedule, and a rationale for their licensing decisions (i.e., choosing GPL 3).

The first project to be released (as of 2008/12/19) is the METS-based bibliographic utility, OpenMIC:

OpenMIC is an open source, web-based cataloging tool that can be used as a standalone application or integrated with other repository architectures by a wide range of organizations. It provides a complete metadata creation system for analog and digital materials, with services to export these metadata in standard formats.

• Low overhead and infrastructure requirements
• Events-based model for management and rights documentation
• Mapping and import from standard and in-house formats
• Unicode and CJK vernacular character support

OpenMIC is a core application for the Moving Image Collections (MIC) initiative developed at the Rutgers University Libraries with funding from the Library of Congress.

I look forward to following along as Rutgers releases yet more of the tools they have developed as part of their impressive digital library infrastructure. It will be even more interesting to hear what their model will be for taking patches / commits from the broader open source community. These things do take time, even though I failed to show an appreciation for that in my original rant, but I am reminded (by Jonathan Rochkind) that it's better to take the time and get it right. I cringe a bit to say that, knowing full well how things tend to languish in committees and fall victim to analysis paralysis in academia; surely there is some middle ground? There are some very talented and experienced folks at Rutgers, so I will be excited to see them take a leadership role in this space.

Go, Scarlet Knights!

I've been using my time at RepoCamp today to get the OAI-ORE plugin for WordPress validating again.  I'm having some trouble using the validator so I say that with some diffidence.  But the latest code which is now checked in to the WordPress plugins svn repo ought to be close, if not fully conformant, to the 0.9 version of the ORE spec.

I'm not sure the plugin is really useful; it's just an Atom feed of all posts and pages in a WP instance.  I can think of some ways to make this more useful, by allowing blog authors to create their own aggregations, pulling in content outside of the particular instance.  I am certain that others can come up with even better uses.  I'm open to suggestions.

Thanks to Jay Datema for prodding me a bit, if indirectly.