tutorial. 查询没有入向引用的tree[math-000A]
一个页面既没有被其他页面链接，也没有被transclude时，我们称它为orphan page。transclude也会把目标页面引入当前页面，因此应当算作一种入向引用。这个查询需要同时查看全站页面、链接和transclusion，所以必须等所有文章都读入并建立Forest后再运行。
本页由Flora的project.scm在分析阶段生成查询结果。项目代码组合Forester提供的pageo、nodeo和node-propertyo，定义自己的关系算子；Grove不需要预先知道“孤立页面”这个项目概念。
把链接和transclusion都表示为入向关系[#124]
link和transclude都直接指向tree ID；不再有heading fragment。incoming-pageo将两种入向引用合并：
(define-relation (incoming-pageo nodes page-id)
(exists (node-id kind)
(either ((== kind 'link)) ((== kind 'transclude)))
(nodeo nodes (node-id node-id) (kind kind))
(node-propertyo nodes node-id 'target page-id))) 先将kind限定为link或transclude，再调用nodeo，它就可以使用kind索引，而不必枚举全站所有节点。miniKanren的目标顺序会影响执行效率。
这里的nodes是Forest中的content-node relation。nodeo找出两类节点，node-propertyo读取目标；两种节点使用同一种tree身份，不需要解析目标字符串。
对有限页面集合做差集[#125]
miniKanren的=/=表示两个项不相等，并不表示“某个关系中不存在匹配行”。这里先查询所有被link或transclude的页面ID，再用递归的not-membero检查一个页面ID不在该有限列表中：
(define-relation (not-membero value values)
(either
((== '() values))
((exists (head tail)
(== `(,head . ,tail) values)
(=/= value head)
(not-membero value tail)))))
(define-relation (authored-pageo page-data page-id title)
(exists (metadata)
(pageo page-data
(page-id page-id)
(title title)
(metadata metadata))
(project (metadata)
(if (assq-ref metadata 'inline-subtree) fail succeed))))
(define-relation (orphan-pageo page-data incoming-page-ids page-id title)
(authored-pageo page-data page-id title)
(not-membero page-id incoming-page-ids))authored-pageo通过pageo排除inline subtree自动生成的页面。这样列出的都是项目中的文章页面，而不是正文里可独立寻址的小节。结果里的链接使用查询专用节点，不会被误记为文章作者创建的入链。
查看当前结果[#126]
构建过程先用incoming-pageo查询入向引用目标，再用orphan-pageo查询剩余文章。结果中的展示链接使用Forester专用的查询链接节点，不会反过来改变入向引用数据：
Found 14 authored pages with no incoming links or transclusions:
- Lesoinne, M.; Farhat, C.: Geometric Conservation Laws for Flow Problems with Moving Boundaries and Deformable Meshes and their Impact on Aeroelastic Computations. AIAA Paper 95-1709, 1995; also in Comp. Meth. Appl. Mech. Eng., 134 (1996), pp. 71-90. (cfd-r2-11)
- Schmatz, M.A.: Hypersonic Three-Dimensional Navier-Stokes Calculations for Equilibrium Gas. AIAA Paper 89-2183, 1989. (cfd-r2-16)
- Slomski, J.F.; Anderson, J.D.; Gorski, J.J.: Effectiveness of Multigrid in Accelerating Convergence of Multidimensional Flows in Chemical Nonequilibrium. AIAA Paper 90-1575, 1990. (cfd-r2-20)
- Li, C.P.: Computational Aspects of Chemically Reacting Flows. AIAA Paper 91-1574, 1991. (cfd-r2-22)
- Young, J.B.; Snoeck, J.: Aerothermodynamics of Low Pressure Steam Turbines and Condensers. Eds. Moore, M.J.; Sieverding, C.H.; Springer Verlag, N.Y., 1987, pp. 87-133. (cfd-r2-26)
- Bakhtar, F.; So, K.S.: A Study of Nucleating Flow of Steam in a Cascade of Supersonic Blading by the Time-Marching Method. Int. J. Heat and Fluid Flow 12 (1991), pp. 54-62. (cfd-r2-27)
- Young, J.B.: Two-Dimensional Non-Equilibrium Wet-Steam Calculations for Nozzles and Turbine Cascades. Trans. ASME, J. Turbomachinery, 114 (1992), pp. 569-579. (cfd-r2-28)
- White, A.J.; Young, J.B.: Time-Marching Method for the Prediction of Two-Dimensional, Unsteady Flows of Condensing Steam. AIAA J. Propulsion and Power, 9 (1993), pp. 579-587. (cfd-r2-29)
- Liberson, A.; Kosolapov, Y.; Rieger, N.; Hesler, S.: Calculation of 3-D Condensing Flows in Nozzles and Turbine Stages. EPRI Nucleation Workshop, Rochester, N.Y., October 24-26, 1995. (cfd-r2-30)
- Bakhtar, F.; Mahpeykar, M.R.; Abbas, K.K.: An Investigation of Nucleating Flows of Steam in a Cascade of Turbine Blading - Theoretical Treatment. Transaction of the ASME 117 (1995), pp. 138-144. (cfd-r2-31)
- Aslan, A.R.; Grundmann, R.: Computation of Three-Dimensional Subsonic Flows in Ducts Using the PNS Approach. ZFW, 14 (1990), Springer Verlag, pp. 373-380. (cfd-r2-36)
- Krishnan, R.R.; Eidson, T.M.: An Efficient, Parallel Space-Marching Euler Solver for HSCT Research. AIAA Paper 95-1749, 1995. (cfd-r2-39)
- Nakahashi, K.; Saitoh, E.: Space-Marching Method on Unstructured grid for Supersonic Flows with Embedded Subsonic Regions. AIAA Paper 96-0418, 1996. (cfd-r2-40)
- 尝试使用Grove (journal-0001)
如果列表为空，说明每篇文章都至少被link或transclude一次。新增文章后，它会自动出现在本页；从其他页面链接或transclude它之后，它会从列表中消失。这一查询展示了项目自定义关系的边界：Forester提供文章与内容节点事实，项目用miniKanren定义自己的谓词，并在有限事实集合上计算结果。