5.2 Opportunities and Challenges of Open GLAM

5.2 Opportunities and Challenges of Open GLAM

Open GLAM presents both opportunities and challenges. Understanding them is crucial to making an informed decision on opening collections. This understanding will allow you to take advantage of the positive outcomes and work around the negative ones. Being able to explain the opportunities and plan for the challenges will help you build a strong argument for open access at your institution or community digitization group.

Learning Outcomes

  1. Understand the opportunities and challenges of Open GLAM
  2. Learn practical ways in which various institutions are seizing the opportunities and facing the challenges of open GLAM

Big Question / Why It Matters

A crucial mission of cultural heritage institutions is to provide access to knowledge and culture to help broaden the understanding that people have about themselves and the world. In doing so, institutions embark on a variety of projects, from on-site educational programs to digitization of works to increase access.

How well prepared are these institutions to reap the benefits of releasing their content? And how will they face the challenges that might appear along the way? How can institutions better support their missions, as well as scholarship and education, while mitigating the negative outcomes of giving away control?

This section will explore the benefits and challenges of open GLAM and look at how a broad understanding can support institutions in implementing open access practices and policies.

Personal Reflection / Why it Matters To You

Have you ever engaged in a conversation about why you think open access is important or how it can be challenging for GLAMs? Ever wonder what institutional case studies might help to build your case for opening access to a collection?

Acquiring Essential Knowledge

Open GLAM有哪些机遇?

在Unit 1,Section 1.3, we provided a short summary of the benefits of open GLAM. Here, we take a deeper dive into some of these, based on over a decade’s worth of GLAM experiences.

One of the best reports that summarizes these benefits is “The Impact of open access on Galleries, Libraries, Museums, & Archives” (2016) written by Effie Kapsalis, Senior Digital Officer at the Smithsonian. She also created a video overview of the report, for apresentation at SXSW 2016(CC BY 3.0):

This report served as a resource for internal advocacy and promotion of open access at the Smithsonian Institution. Kapsalis also identified partners and allies that were showing the value of opening their collection to help her build her case. In February 2020, the Smithsonian launched theiropen access initiative, placing more than 2 million items in the public domain. Imagine trying to display 2 million items in an in-person physical exhibit!

glam拥有惊人的收藏品,而且不可能在一个物理空间同时展示所有这些物品。2011年,利齐·宗马(Lizzy Jongma)加入国立博物馆,担任藏品信息部的数据经理,之后博物馆关闭,并进行了翻修,以扩大空间。但她突然灵光一现。As Lizzy explained forthis profilemade for the book “Made with Creative Commons即使重新装修、扩大空间,博物馆仍然无法展示他们百分之一以上的藏品——100多万件作品中的8000件。

在creasing the visibility of the collection can be easily achieved by using CC tools and licenses. Using such standardized tools to communicate the copyright status as well as use permissions for different works enables search engines to include more multimedia files, including images, from GLAMs into search results. Educators, researchers, artists and general users that are looking for free and open images and content, are more inclined to use the high-quality, openly available content provided by GLAMs.

Benefit: Enhanced mission and relevance to 21st century audiences

Section 5.1we discussed theUNESCO Recommendation concerning the preservation of, and access to, documentary heritage including in digital form.The Implementation Guidelines in the Recommendations affirm:

提供公共访问是记忆机构对社会有效性和有用性的可见证据。这是公共开支用于保护的理由,因为没有无障碍目的的保护是没有意义的。

Several GLAMs decided to implement and expand open access policies to better serve their missions to connect and share with their contemporary audiences. Sharing and dissemination information in digital form is becoming the default mode.

在his Medium article, “我们还需要在线收藏吗.” Adam Moriarty, Head of Information and Library at the Auckland Museum, New Zealand, describes how open access serves the museum’s mission:

“At the Auckland Museum we have a pretty solid mission and vision statement: To enrich lives and inspire discoveries + connect through sharing stories of people, lands and seas. . (…) We went open as a rule, closed open only in exception, released one million records, applied a CC-BY licence to 350,000 images, created an API that follows the principles of linked open data. (…) And we would amplify the Collections through collaboration, partnering with like-minded organisations who shared our passion for open access and already served an audience on a quest for knowledge or creativity.”

By going open, the Auckland Museum engaged with a range of platforms and websites as diverse asPinterest,Digital New Zealand,GBIF(Global Biodiversity Information Facility),Biodiversity Heritage LibraryandWikipedia,这增加了他们的收藏的存在和重用。奥克兰博物馆的实验也增加了他们的数字物品的流量。这反过来又增加了他们收藏的可见性。

GLAMs are often called upon to justify the value of their collections and the impact that they are making. Making collections openly available and thus highly discoverable and usable can justify a GLAM institution’s value — better positioning the institution for continued funding by communicating stakeholder value, their digital collections’ impact, and more.

Think about the mission of your own institution: how would you try to connect it to an open access policy? What language does your institution’s mission use that might advocate for releasing a small collection?

The institution’s mission statements can sometimes feel far away from daily activities, but they are crucial to propose big changes like releasing collections.

Benefit: Foster education through the creation of high quality Open Educational Resources (OER) by allowing the reuse of digital heritage

GLAMs有教育项目,帮助不同类型的观众接触收藏品,并为他们提供了解社会不同方面的学习机会。在tegrating open GLAM collections into education efforts can inform users about GLAM collections and practices, increasingprimary source literacy.重要的是,构建在glam共享的作品和收藏之上的资源可以在开放许可下作为OER(开放教育资源)共享。这些OER和教育策略可以采取不同的形式。

Cover of El archivo en el aula

For example, the project “El archivo en el aula” (“The archive in the classroom”) by Wikimedia Argentina in partnership with theUNESCO Associated Schools Networkand theComisión Nacional Argentina de Cooperación con la Unescodemonstrates what OER anyone can create with released collections.

Benefit: Increased research around collections and collaborations between researchers and institutions

As noted in theUNESCO Recommendation Concerning the Preservation of, and Access to, Documentary Heritage including in Digital Form:

在“数字时代”,获取信息的渠道越来越多。目录和查找工具是必不可少的,但它们现在被大量的数字选项补充:可搜索的在线内容,下载,社交媒体。对于记忆机构来说,有一个网站是至关重要的,包括一个通往他们自己藏品的门户。随着研究人员越来越多地寻求即时回应,一些人很容易认为,如果内容不在互联网上,它就不存在。Catalogues and finding aids, whether analogue or digital, should be structured to international standards so they can be machine readable, globally searchable and linkable.

文物数字化对研究人员具有明显的优势,但对利用馆藏进行研究的文化遗产机构也有一些重要的启示。For example, in her article “关于博物馆藏品,数据能告诉我们什么?,” Diana Greenwald recalls her experience with working with data while she was an Andrew W. Mellon Postdoctoral Curatorial Fellow in 2018 at the National Gallery of Art in the United States. She was able to explore its collections through a different lens just by using the data available about the collections.

Making collections openly available creates new possibilities for research, discoverability, reuse and interpretation. Making collections’ data available also helps building trust and collaboration with outside researchers. Offering your collection in this way also allows researchers to do bulk discovery, exploration and download of data through data dumps. This can bring more value and attention to the collection.

If research is at the core of your institutional mission, but you are unsure where to start, the following might be of interest to you: in 2017 the Institute of Literary Research of the Polish Academy of Sciences, Trinity College Dublin, and Creative Commons Polska had a set of workshops to discuss “How to Facilitate Cooperation between Humanities Researchers and Cultural Heritage Institutions.” As a result, they produced a set ofguidelineswith very illustrative examples of what can be done when institutions and researchers collaborate together through openly available collections. While their focus was on Humanities, some of their conclusions can be applied to other fields.

Benefit: Increased traffic to digital properties and interactions on social media

对于许多glam来说,社交媒体参与为他们的影响力提供了一个相关的衡量标准。At the beginning of the COVID-19 pandemic in 2020, the Getty Museum launchedThe Getty Museum Challenge, as a way to incentivize people to stay connected to art and engage with the museum, while keeping physical distance. The challenge was simple: people were encouraged to create their own version of famous public domain works using household items. The results of the challenge were later published in abook,所有的利润都捐给慈善机构。盖蒂博物馆的开放访问政策为公众远程与机构接触释放了意想不到的创造力和可能性。这个挑战证明了公共领域如何增加社交互动。

Another example is theGIF It Up!由Europeana、DPLA、Digital NZ和Trove联合举办。在2020,The Heritage LaborganizedGIF It Up! Indiafor the first time, with theDAG Museumsbeing the first institution to take part in it. Watch this video with Medhavi Gandhi from The Heritage Lab explaining the importance of social media presence for some institutions, and how the contest helped highlight the importance of open access collections:

And even more benefits…

我们将在与公民科学、众包和公众参与收集相关的即将到来的单元中探索其他益处。Below are additional benefits of releasing collections:

  1. Bringing works in the periphery into focus.当藏品和作品公开时,这些作品会以不同的方式被突出,引起不同用户和公众的关注。详细的元数据和机器可读的版权声明可以增加这些作品的可发现性。
  2. Generation of new narratives around collections in meaningful ways and critical exploration of existing narratives.开放获取允许这些新的叙事和批判性探索采用各种形式,对传统的生产知识的方式提出质疑。混合文化允许新媒体以不同的、有意义的方式审问作品。For a practical example, see this remix of “Mona Lisa vs. David.” For a more theoretical approach, explore Rick Prelinger’s ideas of remix in “On the virtues of pre-existing material.”
  3. 更多的透明度和可视性的集合。
  4. 缓解“版权焦虑。”用户确信,他们可以使用代收货款,而不用担心受到法律制裁。这既适用于公众,也适用于机构内部的专业人员,他们可能不会直接负责权利和复制问题。

What are the challenges of Open GLAM?

There are many benefits to releasing a collection openly. But, of course, there are also challenges. There are several reasons why institutions may not be ready to open access to their collections.

通过与世界各地的机构交流,知识共享了解到许多机构在尝试使用开放许可或工具发布其收藏时所面临的挑卡塔尔vs葡萄牙分析战和恐惧。We could summarize the challenges that many institutions face as concerns over money, attribution or credit[1]和质量。

A more detailed summary includes:

    1. 资金、收入损失和商业模式。在stitutions sometimes are afraid that releasing collections might end up affecting some business models, such as selling photographs, or might negatively impact on revenue streams from other funding sources.
    2. 责任和风险规避。Copyright law can be complicated, and understanding how it applies to specific works or across jurisdictions can create uncertainty that might lead to overly conservative approaches when releasing public domain works.
    3. Bad resolution copies and selling copies of public domain works.Third-party services can use public domain works for commercial purposes, and some institutions might fear that lesser quality versions could end up in the hands of users because of the inability to find the original source in which the digital reproduction of the work was first published.
    4. Uses of public domain works that may cause intentional or unintentional harm.Some uses of public domain works may create societal harm, whether intentional or unintentional, for example, when works are used to convey racist messages.
    5. 错误、混乱或不准确的元数据或信息。在formation and metadata experience changes over time: in the amount of data that is available about works at a given point, in the way in which data about works was represented in previous eras, and in the data input and technologies used to represent it. Some institutions fear that wrong or inaccurate information might represent visions of the world that are not aligned with the values that the institution currently holds.

Alternatively, if an institution is not ready to fully “open” its collections, there are intermediary options available. Anne Young, Director of Legal Affairs and Intellectual Property atNewfields, refers to one option as “Semi Open Access,” which consists of releasing only small portions of the collection to test the waters and assess how comfortable the institution feels with these initial steps. And, as Anne points out, it is also more attainable for a lot of GLAMs. This is important to acknowledge because the resources that institutions have vary greatly.

Challenge: Funding, losing revenues and business models

Depending on what type of collections your institution holds, the process of digitizing materials and maintaining a digital presence can be relatively cheap to very expensive. If you decide to have your own content management system or platform (which does not have to be the case, as some of the examples we have provided show), then it might become more burdensome to maintain.

Funding, both public and private, is crucial for sustaining digitization projects. The funding situation of the GLAM space varies immensely across geographies, with some GLAMs relying mostly on public funding, and others strongly dependent on private funding. Oftentimes, funding comes attached to the results of the digitization being made available under open access policies. Digitization can be an expensive process, and institutions need to have funding for it as the demands of the general public and specific users pivot towards requiring more digital presence.

接受公共资金的机构在实现收入来源多元化方面的压力可能较小。他们主要关心的是以最好的方式完成他们的使命。欧洲航空公司(Europeana)在2011年的一次研讨会上很早就探讨了公共资助机构收入来源的重要性问题。There, they analyzed the fears of revenue loss among European institutions, and one of the recommendations that came out in an after-workshop report “The Problem of the Yellow Milkmaid: A Business Model Perspective on Open Metadata” reads:

“Opening up data should be seen as an important part of the responsibility of our public cultural sector. Instead of measuring success by the amount of commercial revenue that institutions are able to secure from the market, new metrics should be developed that measure the amount of business generated (spill-over) based on data made openly available to the creative industries. This requires a change in evaluation metrics on a policy level.”

However, public funding often does not cover all the costs of digital projects. And for those institutions that do not rely on public money to support costly digital projects, there are legitimate concerns around revenue loss. Revenue loss can express itself as various concerns regarding:

  1. losing revenue from licensing reproduction rights;
  2. losing footfall in the physical space, which impacts the sale of tickets as well as sales in related facilities, like the gift shop or cafeteria;
  3. 投资者愿意支持不像建造或翻新设施那样立即可见或令人印象深刻的项目;and/or
  4. 私营部门的合作伙伴没有对日后可能被利用的数字化或数字版本的作品获得知识产权。

让我们从第一个论点开始。几项研究和经验表明,与版权和复制费用相关的成本实际上是节省的。

  1. Rights & permissions requests cost money.在his seminal study, “Reproduction charging models & rights policy for digital images in American art museums: A Mellon Foundation funded studySimon Tanner发现,有时候权利和许可请求的维护成本实际上比它们给机构带来的整体收入要高。
  2. Open access can make the institution more efficient.减少Rights & Permissions请求的数量可以提高效率。蒂帕帕博物馆仅通过在藏品上添加版权状态声明就减少了约1.4万张图片请求。“我们已经建立了一个强大的、低成本的、集中的系统,用户说他们觉得很容易使用。“ (Reusing Te Papa’s collections images, by the numbers).
  3. 明确的政策和自助式配送减轻了员工的负担。工作人员可以花更多的时间清理尚未数字化的作品的权利,而不是出席已经数字化的作品的请求。它还允许其他部门,如社交媒体和教育部门,能够自助服务,并使用他们可以信任的经过清理的材料,而不必只使用一小批预先选择的内容。For an in-depth exploration on this argument, read Karin Glasemann’s reflection onhow openness transformed the Nationalmuseum

还有一些新的商业模式有待探索。首先,提供收藏并不意味着你需要停止对制作副本的收费,或者你不能为这些数字副本探索不同的商业模式。事实上,数字化需要金钱,在某些情况下,这些成本仍然可以转移到提出特定数字化请求的用户身上,就像许多档案目前所做的那样。重要的是,这些成本需要对用户透明。在开放获取原则下不建议的做法是对在公共领域的作品收取许可费用。在这些案例中,版权主张充其量是可疑的,这违背了该机构向公众提供访问的使命。

An increase in brand licensing is also possible. For example, after The Metropolitan Museum of Art did their major open access release,new branding opportunitiesarose for them. The same was true for the Rijksmuseum, which had the opportunity to do a co-branding campaign with the Dutch brewing company Heineken. Of course, these are major museums with very well known brands, but these are some examples that can also help think differently about how public recognition of the work that institutions do through providing online access to the collection can have an impact. A pilot study conducted by academics: “Reaping the benefits of digitisation: Pilot study exploring revenue generation from digitised collections through technological Innovation,探索了小型机构的其他可能性。

Finally, foot traffic is of major importance for several GLAMs. COVID-19 demonstrated both the importance of these visitors, but also the crucial role that the digital environment played for GLAMs while people were isolated due to public health measures. People actually feel a stronger connection with the institution if it does not set artificial barriers to the content. An increase in the discoverability of the collection also makes people more aware of the existence of GLAM institutions and helps raise awareness of the need to support them.

Challenge: Liability and risk aversion

GLAMs face an inherent tension in dealing with works, irrespective of their nature. This tension arises between their roles as stewards of the physical objects embodying the works in their collection and the fact that most often copyright in the works belongs to someone outside the institution.[2]特别是,版权的严格规则和长期保护影响glam管理对象和公开发布其收藏(部分或全部)的能力。

Additionally, mistakes in releasing collections, such as infringing copyright (even if accidental), can be costly. In some cases, when GLAM communities make works available online, there might be some collaborators that feel that such a use infringes on an implicit social agreement. This is what Patricia Aufderheide and Peter Jaszi have calledthe “permissions culture” in the visual arts(适用于视觉艺术之外的其他领域)。重要的是要了解限制和例外是如何保护您的机构的,但也要提供修复错误的方法。

侵犯版权是导致机构规避风险和害怕承担责任的几个因素之一。然而,仅仅基于风险规避的决策也会影响机构履行其使命的能力。以下是关于制定风险评估策略的一些想法。

  1. 进行清晰、适当的风险评估。Ideally, a proper risk assessment will help assess undue liabilities in the institutions’ decision-making processes. It will also guide staff when making copyright-related decisions. If you or your institution lack experience with risk assessments, we will explore some examples in Section 5.4. For doing these risk assessments, you can rely on your awareness (or access to information about) local laws and court cases.
  2. Offer clear ways to fix mistakes.This is a solution typically used in the case of orphan works, where some institutions have taken their chance to upload and make available some works (even when not necessarily as open access) by offering ways to potential rightsholders to remove those works from the Internet. In any case, it is good practice to have mechanisms in place to solve copyright complaints.
  3. 在机构的需要和公众的需要之间找到平衡。如何平衡托收管理的风险,取决于个别机构、他们的背景和知识。由于害怕未知的法律风险,在标注作品版权信息方面过于保守,包括标明作品属于公共领域,也会产生影响。过于保守的标签和不确定性对作品的重用产生了一种令人不寒而栗的效应,削弱了公共领域内容创造繁荣的公共资源的潜力。

Challenge: Selling bad resolution copies of public domain works

有些网站对机构发布的一些公共领域的作品提供“库存照片”服务,并收取费用。需要注意的是,这些服务是合法的,除非该服务侵犯了该机构的商标或专利权;由于基础作品是在公共领域,即使网站决定对作品的数字复制应用水印,也不存在版权侵权。当GLAM机构决定将CC0应用于数字化作品时,它将发布其可能拥有的任何和所有版权声明。

Of course, this is a frustrating experience for many institutions that have decided to share these works out of their mission to share their collection with the public. It is also problematic from the perspective of quality: some of these services offer poor quality reproductions with watermarks all over them, or even with Technological Protection Measures (TPMs) designed to prevent future reuse.

There may not be a way to avoid these challenges, however, they are outweighed by the many other benefits of releasing a collection.

Also, it is important to note that both people seeking images and search engines will prioritize the good quality websites that offer the free, high resolution, high detailed images, with supporting materials and no watermarks on them. More likely than not, GLAM websites will also offer additional features (from better search capabilities to list-generating capabilities, or the generation of data dumps), which stock photo websites do not provide.

解决库存照片网站挑战的一个好方法不一定是诉诸法律,而是诉诸社会规范。Suggestions include:

  1. 通过解释这些“库存照片”网站的性质来提高用户的意识。如果他们发现你收藏的图片可以购买,让他们知道在你自己的机构网站上有免费、高质量和合法的下载选项。你也可以加上一个警告来提醒人们不要上当受骗。
  2. 相信你的品牌。这些网站的质量存在问题,而一个文化遗产机构的品牌容易被公众识别和信任。
  3. Emphasize the value added you provide. Your institution is not just offering “stock photos,” but also providing context and background to the works that it stewards. That’s a value added.
  4. Keep in mind that charging for digital images is likely not profitable for GLAMs. There is likely a negligible shortfall, if any, for the institution if a stock photo site charges for their photographs.

作为一个普遍的原则,除非用户是搜索一个特定的艺术作品,她将默认使用无风险和无成本的图像。

Challenge: Uses of public domain works that may cause intentional or unintentional harm

公共领域作品的滥用是glam非常关注的问题,特别是当涉及到体现或代表文化敏感内容的作品时。有些演员可能会以你意想不到的方式使用作品,或者让你或其他人感到冒犯。

This “misuse” does not refer to works that for a variety of reasons might not be sensible to release. Indeed, there are some reproductions of works that even while being in the public domain might not be appropriate to release. Such works range from digital copies of photos of human remains to digital reproductions of objects of Indigenous people. We will further discuss the ethical considerations later in the Unit, but a general approach is “open to the extent possible.” There are indeed some ethical considerations to take into account when doing open access releases.

Let us briefly explore some of the use cases that can cause intentional or unintentional harm. One of the most prominent, harmful use cases was that of a public domain work stewarded by the Clark Art Institute, Jean-Léon Gérôme’s “Slave Market” (1866), by the right-wing party Alternative für Deutschland (AfD). While the Clark Art Institutedisapprovedthe use of the public domain image, several months afterward the museum still enacted an Open Access policy, allowing for any reproduction of a public domain work to be downloaded high-resolution for free, as expressed intheir FAQ

The Clark Art Institute example highlights challenges that are not actually about (or within the realm of) copyright. Because the work is in the public domain, copyright is not the right legal mechanism for policing offensive or harmful behavior.

Even if copyright was claimed over the work, copyright protection is not absolute; limitations and exceptions might apply. In other words, even if copyright could be claimed, it may not protect against the particular harm in question.

This case exemplifies that copyright law is not always the best approach to solving challenges of reuse. As in the case of plagiarism, social sanctions and community norms might work better than legal action.

Some social sanctions and community norms to consider:

    1. Publicly disagreeing with the way in which the work was used:if the story is being elevated by the media, the institution can always remind people that although they do not control the use of the work since it’s in the public domain, the institution finds the use harmful, out of context or inaccurate. This strategy however can be counterproductive in some situations, especially if the institution ends up being dragged into a low-brow debate.
    2. Educate audiences about the work:the institution can also use the opportunity to educate its audience about the work. In general, newsflashes might increase the views of certain objects or works; when a public conversation is happening, it is more likely that people will look for that information on the web.[3]That offers the opportunity to bring people’s attention to the context of the work or object, either on the institution’s website or through third-party websites, news outlets, etc.
    3. Offer non-mandatory guidelines or protocols:建立社区规范也是鼓励作品重用的好方法。你可以通过不同的方式来鼓励这种行为,从FAQ部分到按钮,以及当人们下载作品时的提醒,这些都可以作为一种温和的推动。

这些只是社会制裁和社区规范的一些例子,以引发进一步的思考。

Challenge: Wrong, messy or inaccurate metadata or information

Another of GLAMs’ common concerns relates to releasing inaccurate metadata or information about the collection. In some cases, there are historical reasons that explain the inappropriate representation of different groups in metadata. This is a legitimate concern, and there are many workarounds to solve some of the underlying elements.

  1. One way is tomake a disclaimer.在your release, you can explain that some data might actually be inaccurate. This is for example what the Smithsonian did in their release, by adding a question to theirFAQaround “What is the Smithsonian’s commitment to cultural responsibility with open access?”

“Please note that the language and terminology used in this collection reflects the context and culture of the time of its creation, and may include culturally sensitive information. As an historical document, its contents may be at odds with contemporary views and terminology. The information within this collection does not reflect the views of the Smithsonian Institution, but is available in its original form to facilitate research.“

2. Offer ways for improving metadata upon feedback.版本实际上可以帮助改进关于集合的元数据和信息。Look at thissmall exampleof the Swedish Heritage Board collection on Flickr Commons. They uploaded a photo signaling that it was a “monastery,” but a user pointed out that the building depicted was indeed a castle, allowing them to correct a mistake in their records.

3. Explore how collaboration and crowd-sourcing can improve your metadata.Other projects also focus on improving or adding metadata through crowdsourcing, like the trailblazingexampleof the United States Library of Congress: they uploaded part of their collections to Flickr Commons to improve their information about these historical pictures.

Of course, ensuring metadata is usable requires work. But fear of inaccuracies should not prevent this very relevant information from being shared. And last but not least, it is important to remember that “perfect is the enemy of done.” The interaction with users and the public can actually help to improve substantive parts of the information about the collection.

Final remarks

开放馆藏是许多机构吸引当代观众的使命的一个组成部分。发行收藏品有很多好处,重要的是要选择与你的机构、你的机构的使命和你的机构服务的受众产生共鸣的好处。但也有需要评估的挑战。幸运的是,对挑战的意识可以帮助机构提前计划并设计出创造性的解决方案来克服它们。


  1. We will address the element of credit in Section 5.4, when describing different options for an institution to help users provide proper provenance of the works.
  2. 对实物拥有所有权并不意味着机构就是著作权人。实体所有权和版权所有权是分开的、有区别的所有权类型。我们将在第5.3节进一步探讨这一区别。
  3. A good example is to measure the relationship between page views on Wikipedia and events related to celebrities:https://pudding.cool/2018/08/wiki-death/